Recovery Plan for Phytophthora kernoviae Causing Bleeding Trunk Cankers, Leaf Blight and Stem Dieback in Trees and Shrubs

USDA-ARS?s Scientific Manuscript database

Phytophthora kernoviae, a recently described species of Phytophthora, is an invasive pathogen of forest trees and shrubs such as beech (Fagus sylvatica) and rhododendron (Rhododendron ponticum) that has become established in woodlands and public gardens in Cornwall, United Kingdom. Although the ori...

[Dynamics and combined injuries of main pest species in rice cropping zones of Yunnan, Southwest China].

PubMed

Dong, Kun; Dong, Yan; Wang, Hai-Long; Zhang, Li-Min; Zan, Qing-An; Chen, Bin; Li, Zheng-Yue

2014-01-01

A series of rice pest injuries (due to pathogens, insects, and weeds) were surveyed in 286 farmers' fields for major rice varieties of three rice cropping zones of Yunnan Province, Southwest China. The composition and dynamics of main pest species were analyzed, and the trend of rice pest succession in Yunnan was discussed based upon landmark publications. The results showed that the three rice cropping zones had different pest characteristics as regard to main species, dynamics and combined injuries. Sheath rot, bacterial leaf blight, rice stripe, leaf hoppers, armyworms and stem borers were serious in the japonica rice zone. Sheath blight and rice stripe were serious in the japonica-indica interlacing zone. Leaf blast, sheath blight, leaf folders and weeds above rice crop canopy were serious in the indica rice zone. False smut, plant hoppers and weeds below rice crop canopy were ubiquitous and serious in the three kinds of rice cropping zones. Many kinds of weed infestation emerged in the whole rice cropping seasons. Echinochloa crusgalli, Sagittaria pygmaea, Potamogeton distinctus and Spirodela polyrhiza were the main species of weeds in the rice cropping zones of Yunnan. Overall, levels of combined injuries due to pests in the japonica rice zone and the indica rice zone were higher than that in the japonica-indica interlacing zone. In terms of the trend of rice pest succession in Yunnan, injuries due to false smut, sheath blight and plant hoppers seemed to be in a worse tendency in all rice cropping zones of Yunnan, while dominants species of weeds in the paddy fields are shifting from the annual weeds to the perennial malignant weeds.

Transgenic American chestnuts show enhanced blight resistance and transmit the trait to T1 progeny.

PubMed

Newhouse, Andrew E; Polin-McGuigan, Linda D; Baier, Kathleen A; Valletta, Kristia E R; Rottmann, William H; Tschaplinski, Timothy J; Maynard, Charles A; Powell, William A

2014-11-01

American chestnut (Castanea dentata) is a classic example of a native keystone species that was nearly eradicated by an introduced fungal pathogen. This report describes progress made toward producing a fully American chestnut tree with enhanced resistance to the blight fungus (Cryphonectria parasitica). The transgenic American chestnut 'Darling4,' produced through an Agrobacterium co-transformation procedure to express a wheat oxalate oxidase gene driven by the VspB vascular promoter, shows enhanced blight resistance at a level intermediate between susceptible American chestnut and resistant Chinese chestnut (Castanea mollissima). Enhanced resistance was identified first with a leaf-inoculation assay using young chestnuts grown indoors, and confirmed with traditional stem inoculations on 3- and 4-year-old field-grown trees. Pollen from 'Darling4' and other events was used to produce transgenic T1 seedlings, which also expressed the enhanced resistance trait in leaf assays. Outcrossed transgenic seedlings have several advantages over tissue-cultured plantlets, including increased genetic diversity and faster initial growth. This represents a major step toward the restoration of the majestic American chestnut. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

Novel species of Botryosphaeriaceae associated with shoot blight of pistachio.

PubMed

Chen, ShuaiFei; Li, GuoQing; Liu, FeiFei; Michailides, Themis J

2015-01-01

Various species of phytopathogenic Botryosphaeriaceae were identified previously from pistachio trees worldwide. Disease symptoms caused by pathogens in Botryosphaeriaceae on pistachio include panicle and shoot blight, leaf defoliation, fruit discoloration and decay. In this study species of Botryosphaeriaceae were collected from blighted pistachio shoots in Arizona, USA, and Greece. The aims of this study were to identify these Botryosphaeriaceae isolates and to test their pathogenicity to pistachio. The fungi were identified based on comparisons of DNA sequence data of the nuclear rDNA internal transcribed spacer region (ITS), a partial translation elongation factor 1-alpha gene (TEF1), a partial β-tubulin gene (TUB2) and morphological characteristics. Results indicated that some isolates collected from pistachio represent two previously undescribed species, which we described here as Lasiodiplodia americana sp. nov. from the United States and Neofusicoccum hellenicum sp. nov. from Greece. Field inoculations of L. americana and N. hellenicum on branches of four pistachio cultivars showed that both L. americana and N. hellenicum are pathogenic on pistachio. The four pistachio cultivars differed in their susceptibility to the Botryosphaeriaceae species. Results of this study suggested that the two new species of Botryosphaeriaceae need to be monitored carefully to determine the distribution of these pathogens and the possible spread to other areas. © 2015 by The Mycological Society of America.

Management of foliar infection of Rhododendron by Phytophthora ramorum with film forming polymers and surfactants

Treesearch

Ebba K. Peterson; Eric Larson

2017-01-01

Phytophthora ramorum, causal agent of sudden oak death (SOD) and ramorum leaf blight, remains a persistent problem of regulatory concern within the horticultural industry. Damages to nurseries have been realized as a result of enforced quarantine and sanitation efforts designed to prevent the spread and establishment of this invasive pathogen....

Draft genome sequences of Chrysoporthe austroafricana, Diplodia scrobiculata, Fusarium nygamai, Leptographium lundbergii, Limonomyces culmigenus, Stagonosporopsis tanaceti, and Thielaviopsis punctulata

USDA-ARS?s Scientific Manuscript database

Basidiomycete fungi in the genus Limonomyces are important pathogens of turfgrasses, causing pink patch and cream leaf blight diseases on numerous grass hosts worldwide. Much is unknown about the biology and taxonomy of these fungi, and molecular resources are extremely rare. Here, we report draft...

Effectiveness of a detached‐leaf assay as a proxy for stem inoculations in backcrossed chestnut (Castanea) blight resistance breeding populations

Treesearch

N. R. LaBonte; J.R. McKenna; K. Woeste

2016-01-01

A recently developed detached-leaf blight resistance assay has generated interest because it could reduce the amount of time needed to evaluate backcrossed hybrid trees in the American chestnut blight resistance breeding programme. We evaluated the leaf inoculation technique on a sample of advanced progeny from the Indiana state chapter American Chestnut Foundation...

‘Carolina Broadleaf’ mustard green (Brassica juncea L.) resistant to the bacterial leaf blight pathogen Pseudomonas cannabina pv. alisalensis

USDA-ARS?s Scientific Manuscript database

A leafy-green mustard (Brassica juncea L.) cultivar designated ‘Carolina Broadleaf’ has been released by the Agricultural Research Service of the U.S. Dept. of Agriculture in 2015. This released cultivar is a narrow-based population of leafy-green mustard derived from a U.S. plant introduction (PI)...

Fire behavioral changes as a result of sudden oak death in coastal California forests

Treesearch

Y. Vlachovic; C. Lee; H. Scanlon; J.M. Varner; R. Glebocki; B.D. Graham; D.M. Rizzo

2013-01-01

Field observations and anecdotal evidence suggest that sudden oak death (SOD), a disease caused by the pathogen Phytophthora ramorum, may alter fuel loading in affected forests. Though it is reasonable to assume that a disease resulting in leaf blight, dead branches, and tree mortality would increase forest fuels, little work has been done to...

Gnomonia canker, shoot blight, and leaf spot of yellow birch.

Treesearch

Kenneth J. Jr. Kessler

1978-01-01

Describes a canker, shoot blight, and leaf spot disease of yellow birch seedlings in the northern Great Lakes region and tells how and when trees become infected by the fungal causal agent, Gnomonia setacea.

Constitutive expression of the xylanase inhibitor TAXI-III delays Fusarium head blight symptoms in durum wheat transgenic plants.

PubMed

Moscetti, Ilaria; Tundo, Silvio; Janni, Michela; Sella, Luca; Gazzetti, Katia; Tauzin, Alexandra; Giardina, Thierry; Masci, Stefania; Favaron, Francesco; D'Ovidio, Renato

2013-12-01

Cereals contain xylanase inhibitor (XI) proteins which inhibit microbial xylanases and are considered part of the defense mechanisms to counteract microbial pathogens. Nevertheless, in planta evidence for this role has not been reported yet. Therefore, we produced a number of transgenic plants constitutively overexpressing TAXI-III, a member of the TAXI type XI that is induced by pathogen infection. Results showed that TAXI-III endows the transgenic wheat with new inhibition capacities. We also showed that TAXI-III is correctly secreted into the apoplast and possesses the expected inhibition parameters against microbial xylanases. The new inhibition properties of the transgenic plants correlate with a significant delay of Fusarium head blight disease symptoms caused by Fusarium graminearum but do not significantly influence leaf spot symptoms caused by Bipolaris sorokiniana. We showed that this contrasting result can be due to the different capacity of TAXI-III to inhibit the xylanase activity of these two fungal pathogens. These results provide, for the first time, clear evidence in planta that XI are involved in plant defense against fungal pathogens and show the potential to manipulate TAXI-III accumulation to improve wheat resistance against F. graminearum.

Effects of neolignans from the stem bark of Magnolia obovata on plant pathogenic fungi.

PubMed

Choi, N H; Choi, G J; Min, B-S; Jang, K S; Choi, Y H; Kang, M S; Park, M S; Choi, J E; Bae, B K; Kim, J-C

2009-06-01

To characterize antifungal principles from the methanol extract of Magnolia obovata and to evaluate their antifungal activities against various plant pathogenic fungi. Four neolignans were isolated from stem bark of M. obovata as antifungal principles and identified as magnolol, honokiol, 4-methoxyhonokiol and obovatol. In mycelial growth inhibition assay, both magnolol and honokiol displayed more potent antifungal activity than 4-methoxyhonokiol and obovatol. Both magnolol and honokiol showed similar in vivo antifungal spectrum against seven plant diseases tested; both compounds effectively suppressed the development of rice blast, tomato late blight, wheat leaf rust and red pepper anthracnose. 4-Methoxyhonokiol and obovatol were highly active to only rice blast and wheat leaf rust respectively. The extract of M. obovata and four neolignans had potent in vivo antifungal activities against plant pathogenic fungi. Neolignans from Magnolia spp. can be used and suggested as a novel antifungal lead compound for the development of new fungicide and directly as a natural fungicide for the control of plant diseases such as rice blast and wheat leaf rust.

Addition of transcription activator-like effector binding sites to a pathogen strain-specific rice bacterial blight resistance gene makes it effective against additional strains and against bacterial leaf streak.

PubMed

Hummel, Aaron W; Doyle, Erin L; Bogdanove, Adam J

2012-09-01

Xanthomonas transcription activator-like (TAL) effectors promote disease in plants by binding to and activating host susceptibility genes. Plants counter with TAL effector-activated executor resistance genes, which cause host cell death and block disease progression. We asked whether the functional specificity of an executor gene could be broadened by adding different TAL effector binding elements (EBEs) to it. We added six EBEs to the rice Xa27 gene, which confers resistance to strains of the bacterial blight pathogen Xanthomonas oryzae pv. oryzae (Xoo) that deliver the TAL effector AvrXa27. The EBEs correspond to three other effectors from Xoo strain PXO99(A) and three from strain BLS256 of the bacterial leaf streak pathogen Xanthomonas oryzae pv. oryzicola (Xoc). Stable integration into rice produced healthy lines exhibiting gene activation by each TAL effector, and resistance to PXO99(A) , a PXO99(A) derivative lacking AvrXa27, and BLS256, as well as two other Xoo and 10 Xoc strains virulent toward wildtype Xa27 plants. Transcripts initiated primarily at a common site. Sequences in the EBEs were found to occur nonrandomly in rice promoters, suggesting an overlap with endogenous regulatory sequences. Thus, executor gene specificity can be broadened by adding EBEs, but caution is warranted because of the possible coincident introduction of endogenous regulatory elements. © 2012 The Authors. New Phytologist © 2012 New Phytologist Trust.

Comparative transcript profiling by SuperSAGE identifies novel candidate genes for controlling potato quantitative resistance to late blight not compromised by late maturity.

PubMed

Draffehn, Astrid M; Li, Li; Krezdorn, Nicolas; Ding, Jia; Lübeck, Jens; Strahwald, Josef; Muktar, Meki S; Walkemeier, Birgit; Rotter, Björn; Gebhardt, Christiane

2013-01-01

Resistance to pathogens is essential for survival of wild and cultivated plants. Pathogen susceptibility causes major losses of crop yield and quality. Durable field resistance combined with high yield and other superior agronomic characters are therefore, important objectives in every crop breeding program. Precision and efficacy of resistance breeding can be enhanced by molecular diagnostic tools, which result from knowledge of the molecular basis of resistance and susceptibility. Breeding uses resistance conferred by single R genes and polygenic quantitative resistance. The latter is partial but considered more durable. Molecular mechanisms of plant pathogen interactions are elucidated mainly in experimental systems involving single R genes, whereas most genes important for quantitative resistance in crops like potato are unknown. Quantitative resistance of potato to Phytophthora infestans causing late blight is often compromised by late plant maturity, a negative agronomic character. Our objective was to identify candidate genes for quantitative resistance to late blight not compromised by late plant maturity. We used diagnostic DNA-markers to select plants with different field levels of maturity corrected resistance (MCR) to late blight and compared their leaf transcriptomes before and after infection with P. infestans using SuperSAGE (serial analysis of gene expression) technology and next generation sequencing. We identified 2034 transcripts up or down regulated upon infection, including a homolog of the kiwi fruit allergen kiwellin. 806 transcripts showed differential expression between groups of genotypes with contrasting MCR levels. The observed expression patterns suggest that MCR is in part controlled by differential transcript levels in uninfected plants. Functional annotation suggests that, besides biotic and abiotic stress responses, general cellular processes such as photosynthesis, protein biosynthesis, and degradation play a role in MCR.

Comparative study on the effect of chemicals on Alternaria blight in Indian mustard--a multi-location study in India.

PubMed

Meena, P D; Chattopadhyay, C; Kumar, A; Awasthi, R P; Singh, R; Kaur, S; Thomas, L; Goyal, P; Chand, P

2011-05-01

High severity of Altemaria blight disease is a major constraint in production of rapeseed-mustard in India. The aim of this study was to investigate the suppressive potential of chemicals viz., zinc sulphate, borax, sulphur, potash and calcium sulphate, aqueous extracts viz., Eucalyptus globosus (50 g l-1) leaf extract and garlic (Allium sativum) bulb (20 g l-1) extract, cow urine and bio-agents Trichoderma harzianum, Pseudomonas fluorescence in comparison with the recommended chemical fungicide (mancozeb), against foliar disease Alternaria blight of Indian mustard [Brassica juncea (L.) Czern. and Coss] under five different geographical locations of India. Mancozeb recorded the lowest mean severity (leaf: 33.1%; pod: 26.3%) of Alternaria blight with efficacy of garlic bulb extract alone (leaf = 34.4%; pod = 27.3%) or in combination with cow urine (leaf = 34.2%; pod = 28.6%) being statistically at par with the recommended chemical fungicide. Chemicals also proved effective in reducing Alternaria blight severity on leaves and pods of Indian mustard (leaf = 36.3-37.9%; pod = 27.5-30.1%). The effective treatments besides providing significant reduction in disease severity also enabled increase in dry seed yield of the crop (mancozeb = 2052 kg ha-1; garlic = 2006 kg ha-1; control = 1561 kg ha-1).

Maculosin, a host-specific phytotoxin for spotted knapweed from Alternaria alternata

PubMed Central

Stierle, Andrea C.; Cardellina, John H.; Strobel, Gary A.

1988-01-01

Several diketopiperazines have been isolated from liquid cultures of Alternaria alternata, the causal agent of black leaf blight of spotted knapweed, Centaurea maculosa Lam. One of these compounds, maculosin [the diketopiperazine cyclo(-L-Pro-L-Tyr-)], was active in the nicked-leaf bioassay at 10-5 M; synthetic maculosin possessed chemical and biological activities identical to those of the natural product. Other diketopiperazines isolated from the fungus possessed either less activity or none at all. In tests against 19 plant species, maculosin was phytotoxic only to spotted knapweed. Thus maculosin is a host-specific phytotoxin from a weed pathogen. PMID:16593989

Dehydro-alpha-lapachone isolated from Catalpa ovata stems: activity against plant pathogenic fungi.

PubMed

Cho, Jun Young; Kim, Hae Young; Choi, Gyung Ja; Jang, Kyoung Soo; Lim, He Kyoung; Lim, Chi Hwan; Cho, Kwang Yun; Kim, Jin-Cheol

2006-05-01

The methanol extract of stems of Catalpa ovata G Don exhibits potent in vivo antifungal activity against Magnaporthe grisea (Hebert) Barr (rice blast) on rice plants, Botrytis cinerea Pers ex Fr (tomato grey mould) and Phytophthora infestans (Mont) de Bary (tomato late blight) on tomato plants, Puccinia recondita Rob ex Desm (wheat leaf rust) on wheat plants and Blumeria graminis (DC) Speer f. sp. hordei Marchal (barley powdery mildew) on barley plants. An antifungal substance was isolated and identified as dehydro-alpha-lapachone from mass and nuclear magnetic resonance spectral data. It completely inhibited the mycelial growth of B. cinerea, Colletotrichum acutatum Simmonds, Colletotrichum gloeosporioides Simmonds, M. grisea and Pythium ultimum Trow over a range of 0.4-33.3 mg litre(-1). It also controlled the development of rice blast, tomato late blight, wheat leaf rust, barley powdery mildew and red pepper anthracnose (Colletotrichum coccodes (Wallr) S Hughes). The chemical was particularly effective in suppressing red pepper anthracnose by 95% at a concentration of 125 mg litre(-1). Copyright 2006 Society of Chemical Industry.

Results of the 1971 Corn Blight Watch experiment

NASA Technical Reports Server (NTRS)

Macdonald, R. B.; Allen, R. D.; Bauer, M. E.; Clifton, J. W.; Frickson, J. D.; Landgrebe, D. A.

1972-01-01

Advanced remote sensing techniques are used to: (1)Detect development and spread of corn leaf blight during the growing season; (2) assess the extent and severity of blight infection; (3) assess the impact of blight on corn production; and (4) estimate the applicability of these techniques to similar situations occurring in the future.

The Diaporthe sojae species complex: Phylogenetic re-assessment of pathogens associated with soybean, cucurbits and other field crops.

PubMed

Udayanga, Dhanushka; Castlebury, Lisa A; Rossman, Amy Y; Chukeatirote, Ekachai; Hyde, Kevin D

2015-05-01

Phytopathogenic species of Diaporthe are associated with a number of soybean diseases including seed decay, pod and stem blight and stem canker and lead to considerable crop production losses worldwide. Accurate morphological identification of the species that cause these diseases has been difficult. In this study, we determined the phylogenetic relationships and species boundaries of Diaporthe longicolla, Diaporthe phaseolorum, Diaporthe sojae and closely related taxa. Species boundaries for this complex were determined based on combined phylogenetic analysis of five gene regions: partial sequences of calmodulin (CAL), beta-tubulin (TUB), histone-3 (HIS), translation elongation factor 1-α (EF1-α), and the nuclear ribosomal internal transcribed spacers (ITS). Phylogenetic analyses revealed that this large complex of taxa is comprised of soybean pathogens as well as species associated with herbaceous field crops and weeds. Diaporthe arctii, Diaporthe batatas, D. phaseolorum and D. sojae are epitypified. The seed decay pathogen D. longicolla was determined to be distinct from D. sojae. D. phaseolorum, originally associated with stem and leaf blight of Lima bean, was not found to be associated with soybean. A new species, Diaporthe ueckerae on Cucumis melo, is introduced with description and illustrations. Published by Elsevier Ltd.

Green tissue-specific co-expression of chitinase and oxalate oxidase 4 genes in rice for enhanced resistance against sheath blight.

PubMed

Karmakar, Subhasis; Molla, Kutubuddin Ali; Chanda, Palas K; Sarkar, Sailendra Nath; Datta, Swapan K; Datta, Karabi

2016-01-01

Green tissue-specific simultaneous overexpression of two defense-related genes ( OsCHI11 & OsOXO4 ) in rice leads to significant resistance against sheath blight pathogen ( R. solani ) without distressing any agronomically important traits. Overexpressing two defense-related genes (OsOXO4 and OsCHI11) cloned from rice is effective at enhancing resistance against sheath blight caused by Rhizoctonia solani. These genes were expressed under the control of two different green tissue-specific promoters, viz. maize phosphoenolpyruvate carboxylase gene promoter, PEPC, and rice cis-acting 544-bp DNA element, immediately upstream of the D54O translational start site, P D54O-544 . Putative T0 transgenic rice plants were screened by PCR and integration of genes was confirmed by Southern hybridization of progeny (T1) rice plants. Successful expression of OsOXO4 and OsCHI11 in all tested plants was confirmed. Expression of PR genes increased significantly following pathogen infection in overexpressing transgenic plants. Following infection, transgenic plants exhibited elevated hydrogen peroxide levels, significant changes in activity of ROS scavenging enzymes and reduced membrane damage when compared to their wild-type counterpart. In a Rhizoctonia solani toxin assay, a detached leaf inoculation test and an in vivo plant bioassay, transgenic plants showed a significant reduction in disease symptoms in comparison to non-transgenic control plants. This is the first report of overexpression of two different PR genes driven by two green tissue-specific promoters providing enhanced sheath blight resistance in transgenic rice.

Efficacy of bacillus biocontrol agents for management of sheath blight and narrow brown leaf spot in organic rice

USDA-ARS?s Scientific Manuscript database

Organic rice production has significantly increased in the U. S. over the last decade. Growers lack effective tools to manage sheath blight, caused by Rhizoctonia solani, and narrow brown leaf spot (NBLS), caused by Cercospora janseana, two major diseases affecting organic rice production. An experi...

Southern corn leaf blight a story worth retelling

USDA-ARS?s Scientific Manuscript database

The Southern Corn Leaf Blight Epidemic of 1970-1971 was one of the most costly disease outbreaks to affect North American agriculture, destroying 15% of the crop at a cost of $1.0 billion (US). It resulted from an over reliance on cytoplasmic Texas male sterile (cms-T) lines in hybrid seed producti...

Corn blight watch experiment results

NASA Technical Reports Server (NTRS)

Johannsen, C. J.; Bauer, M. E.

1972-01-01

Results pertaining to the detection and assessment of the severity and extent of southern corn leaf blight in the Corn Belt area are discussed. Ground observations, interpretation of color infrared photography, and machine analysis of multispectral scanner data were used to identify the blight.

South American Leaf Blight of the Rubber Tree (Hevea spp.): New Steps in Plant Domestication using Physiological Features and Molecular Markers

PubMed Central

Lieberei, Reinhard

2007-01-01

Background Rubber trees (Hevea spp.) are perennial crops of Amazonian origin that have been spread over the whole tropical belt to guarantee worldwide production of natural rubber. This crop plant has found its place in many national economies of producing countries, and although its domestication by selection of suitable genotypes was very slow, it contributes a lot to the welfare of small farmers worldwide. Its development is limited by severe diseases. In South America, the main fungal disease of rubber trees is the South American leaf blight (SALB) caused by the ascomycete Microcyclus ulei. This fungus inhibits natural rubber production on a commercial scale in South and Central America. Scope The disease is still restricted to its continent of origin, but its potential to be distributed around the world rises with every transcontinental airline connection that directly links tropical regions. The need to develop control measures against the disease is an urgent task and must be carried out on an international scale. All control efforts so far taken since 1910 have ended in a miserable failure. Even the use of modern systemic fungicides and use of greatly improved application techniques have failed to prevent large losses and dieback of trees. The results of research dealing with both the disease and the pathosystem over more than 50 years are summarized and placed into perspective. Future Prospects A detailed knowledge of this host–pathogen combination requires understanding of the dynamics of Hevea leaf development, the biochemical potential for cyanide liberation, and molecular data for several types of resistance factors. Resolution of the Hevea–SALB problem may serve as a model for future host–pathogen studies of perennial plants requiring a holistic approach. PMID:17650512

First report of a new leaf blight caused by Phacidiopycnis washingtonensis on Pacific Madrone in Western Washington and Oregon

USDA-ARS?s Scientific Manuscript database

In recent years, an unknown leaf blight disease, consisting of browned, desiccated leaves occurring mainly in the lower parts of the canopy, has been observed during periods of wet springs on Pacific madrone (Arbutus menziesii) in western Washington and Oregon. In May 2009 and 2011 severe outbreaks ...

Large scale field inoculation and scoring of maize southern leaf blight and other maize foliar fungal diseases

USDA-ARS?s Scientific Manuscript database

Field-grown maize is inoculated with Cochliobolus heterostrophus, causal agent of Southern Leaf Blight disease, by dropping sorghum grains infested with the fungus into the whorl of each maize plant at an early stage of growth. The initial lesions produce secondary inoculum that is dispersed by wind...

Field evaluation of leaf blight-resistant plant introductions of Brassica Juncea and Brassica Rapa and elucidation of inheritance of resistance

USDA-ARS?s Scientific Manuscript database

Brassica leafy greens (Brassica juncea and Brassica rapa) represent one of the most economically important vegetable crop groups in the southeastern United States. In the last 10 years, numerous occurrences of a leaf blight disease on these leafy vegetables have been reported in several states. One ...

Detection of gene expression changes in Capsicum annuum L. leaf foliar blight caused by Phytophthora capsici Leon. using qRT-PCR and leaf discs

USDA-ARS?s Scientific Manuscript database

Phytophthora capsici is responsible for multiple disease syndromes of Capsicum annuum but the resistance mechanism is still unknown. Evaluating gene expression during foliar blight can be used to identify expression patterns associated with resistance in Capsicum species. This study reports a direct...

Identification of Teosinte (Zea mays ssp. parviglumis) alleles for resistance to southern leaf blight in near isogenic maize lines

USDA-ARS?s Scientific Manuscript database

Southern Leaf Blight [(SLB), causal agent Cochliobolus heterostrophus race O] is an important fungal disease of maize in the United States. Teosinte (Zea mays ssp. parviglumis), the wild progenitor of maize, offers a novel source of resistance alleles that may have been lost during domestication. T...

Expression of Rice Chitinase Gene in Genetically Engineered Tomato Confers Enhanced Resistance to Fusarium Wilt and Early Blight

PubMed Central

Jabeen, Nyla; Chaudhary, Zubeda; Gulfraz, Muhammad; Rashid, Hamid; Mirza, Bushra

2015-01-01

This is the first study reporting the evaluation of transgenic lines of tomato harboring rice chitinase (RCG3) gene for resistance to two important fungal pathogens Fusarium oxysporum f. sp. lycopersici (Fol) causing fusarium wilt and Alternaria solani causing early blight (EB). In this study, three transgenic lines TL1, TL2 and TL3 of tomato Solanum lycopersicum Mill. cv. Riogrande genetically engineered with rice chitinase (RCG 3) gene and their R1 progeny was tested for resistance to Fol by root dip method and A. solani by detached leaf assay. All the R0 transgenic lines were highly resistant to these fungal pathogens compared to non-transgenic control plants. The pattern of segregation of three independent transformant for Fol and A. solani was also studied. Mendelian segregation was observed in transgenic lines 2 and 3 while it was not observed in transgenic line 1. It was concluded that introduction of chitinase gene in susceptible cultivar of tomato not only enhanced the resistance but was stably inherited in transgenic lines 2 and 3. PMID:26361473

Invasion of Solanum tuberosum L. by Aspergillus terreus: a microscopic and proteomics insight on pathogenicity.

PubMed

Louis, Bengyella; Waikhom, Sayanika Devi; Roy, Pranab; Bhardwaj, Pardeep Kumar; Singh, Mohendro Wakambam; Chandradev, Sharma K; Talukdar, Narayan Chandra

2014-06-10

Aspergillus terreus is one of the most harmful filamentous fungal pathogen of humans, animals and plants. Recently, researchers have discovered that A. terreus can cause foliar blight disease in potato (Solanum tuberosum L.). We used light and scanning electron microscopy, and performed proteomics analysis in an attempt to dissect the invasion process of A. terreus in this important crop. Microscopic study revealed that invasion of leaf tissue is marked by rapid germination of A. terreus phialidic conidia (PC) by 4 h after inoculation. By 8 h after inoculation, primary germ tubes from PC differentiated into irregular protuberance, often displayed stomata atropism, and failed to penetrate via the epidermal cells. Colonization of leaf tissues was associated with high rate of production of accessory conidia (AC). These analyses showed the occurrence of a unique opposing pattern of AC, tissue-specific and produced on melanized colonizing hyphae during the infection of leaf tissue. A significant proteome change hallmarked by differential expression of class I patatin, lipoxygenase, catalase-peroxidase complex, and cysteine proteinase inhibitor were observed during tuber colonization. These proteins are often involved in signal transduction pathways and crosstalk in pathogenic responses. A. terreus abundantly produced AC and multipolar germinating PC to invade potato leaf tissue. Additionally, A. terreus differentially induced enzymes in potato tuber during colonization which facilitates rapid disease development.

Invasion of Solanum tuberosum L. by Aspergillus terreus: a microscopic and proteomics insight on pathogenicity

PubMed Central

2014-01-01

Background Aspergillus terreus is one of the most harmful filamentous fungal pathogen of humans, animals and plants. Recently, researchers have discovered that A. terreus can cause foliar blight disease in potato (Solanum tuberosum L.). We used light and scanning electron microscopy, and performed proteomics analysis in an attempt to dissect the invasion process of A. terreus in this important crop. Results Microscopic study revealed that invasion of leaf tissue is marked by rapid germination of A. terreus phialidic conidia (PC) by 4 h after inoculation. By 8 h after inoculation, primary germ tubes from PC differentiated into irregular protuberance, often displayed stomata atropism, and failed to penetrate via the epidermal cells. Colonization of leaf tissues was associated with high rate of production of accessory conidia (AC). These analyses showed the occurrence of a unique opposing pattern of AC, tissue-specific and produced on melanized colonizing hyphae during the infection of leaf tissue. A significant proteome change hallmarked by differential expression of class I patatin, lipoxygenase, catalase-peroxidase complex, and cysteine proteinase inhibitor were observed during tuber colonization. These proteins are often involved in signal transduction pathways and crosstalk in pathogenic responses. Conclusion A. terreus abundantly produced AC and multipolar germinating PC to invade potato leaf tissue. Additionally, A. terreus differentially induced enzymes in potato tuber during colonization which facilitates rapid disease development. PMID:24917207

The corn blight problem: 1970 and 1971

NASA Technical Reports Server (NTRS)

Bauer, M. E.

1972-01-01

Southern corn leaf blight is caused by the fungus, Helminthosporium maydis. Race T of H maydis adapted itself to the Texas male sterile cytoplasm corn. The problems caused by this variety of the blight in 1970 and 1971 are discussed, as well as the symptoms and development of the disease.

Enhanced resistance to blister blight in transgenic tea (Camellia sinensis [L.] O. Kuntze) by overexpression of class I chitinase gene from potato (Solanum tuberosum).

PubMed

Singh, H Ranjit; Deka, Manab; Das, Sudripta

2015-07-01

Tea is the second most consumed beverage in the world. A crop loss of up to 43 % has been reported due to blister blight disease of tea caused by a fungus, Exobasidium vexans. Thus, it directly affects the tea industry qualitatively and quantitatively. Solanum tuberosum class I chitinase gene (AF153195) is a plant pathogenesis-related gene. It was introduced into tea genome via Agrobacterium-mediated transformation with hygromycin phosphotransferase (hpt) gene conferring hygromycin resistance as plant selectable marker. A total of 41 hygromycin resistant plantlets were obtained, and PCR analysis established 12 plantlets confirming about the stable integration of transgene in the plant genome. Real-time PCR detected transgene expression in four transgenic plantlets (T28, C57, C9, and T31). Resistance to biotrophic fungal pathogen, E. vexans, was tested by detached leaf infection assay of greenhouse acclimated plantlets. An inhibitory activity against the fungal pathogen was evident from the detached leaves from the transformants compared with the control. Fungal lesion formed on control plantlet whereas the transgenic plantlets showed resistance to inoculated fungal pathogen by the formation of hypersensitivity reaction area. This result suggests that constitutive expression of the potato class I chitinase gene can be exploited to improve resistance to fungal pathogen, E. vexans, in economical perennial plantation crop like tea.

Fusarium species as pathogen on orchids.

PubMed

Srivastava, Shikha; Kadooka, Chris; Uchida, Janice Y

2018-03-01

The recent surge in demand for exotic ornamental crops such as orchids has led to a rise in international production, and a sharp increase in the number of plant and plant products moving between countries. Along with the plants, diseases are also being transported and introduced into new areas. Fusarium is one of the major diseases causing pathogens infecting orchids that is spreading through international trade. Studies have identified several species of Fusarium associated with orchids, some are pathogenic and cause symptoms such as leaf and flower spots, leaf or sheath blights, pseudostem or root rots, and wilts. Infection and damage caused by Fusarium reduces the quality of plants and flowers, and can cause severe economic losses. This review documents the current status of the Fusarium-orchid interaction, and illustrates challenges and future perspectives based on the available literature. This review is the first of Fusarium and orchid interactions, and integrates diverse results that both furthers the understanding and knowledge of this disease complex, and will enable the development of effective disease management practices. Copyright © 2017 Elsevier GmbH. All rights reserved.

A severe epidemic of Marssonina leaf blight on quaking aspen in Northern Utah

Treesearch

Roy O. Harniss; David L. Nelson

1984-01-01

The extent of Marssonina leaf blight (Marssonina populi) on quaking aspen (Populus tremuloides) was observed in northern Utah and adjacent States in 1981 aand 1982. Area of the epidemic and symptoms of the disease are described. On 1,000 acres (405 hal) in northern Utah, infection levels were 6 percent slight, 12 percent light, 32 percent moderate, 16 percent...

The durable wheat disease resistance gene Lr34 confers common rust and northern corn leaf blight resistance in maize.

PubMed

Sucher, Justine; Boni, Rainer; Yang, Ping; Rogowsky, Peter; Büchner, Heike; Kastner, Christine; Kumlehn, Jochen; Krattinger, Simon G; Keller, Beat

2017-04-01

Maize (corn) is one of the most widely grown cereal crops globally. Fungal diseases of maize cause significant economic damage by reducing maize yields and by increasing input costs for disease management. The most sustainable control of maize diseases is through the release and planting of maize cultivars with durable disease resistance. The wheat gene Lr34 provides durable and partial field resistance against multiple fungal diseases of wheat, including three wheat rust pathogens and wheat powdery mildew. Because of its unique qualities, Lr34 became a cornerstone in many wheat disease resistance programmes. The Lr34 resistance is encoded by a rare variant of an ATP-binding cassette (ABC) transporter that evolved after wheat domestication. An Lr34-like disease resistance phenotype has not been reported in other cereal species, including maize. Here, we transformed the Lr34 resistance gene into the maize hybrid Hi-II. Lr34-expressing maize plants showed increased resistance against the biotrophic fungal disease common rust and the hemi-biotrophic disease northern corn leaf blight. Furthermore, the Lr34-expressing maize plants developed a late leaf tip necrosis phenotype, without negative impact on plant growth. With this and previous reports, it could be shown that Lr34 is effective against various biotrophic and hemi-biotrophic diseases that collectively parasitize all major cereal crop species. © 2016 The Authors. Plant Biotechnology Journal published by Society for Experimental Biology and The Association of Applied Biologists and John Wiley & Sons Ltd.

Comparative population genomics of Fusarium graminearum reveals adaptive divergence among cereal head blight pathogens

USDA-ARS?s Scientific Manuscript database

In this study we sequenced the genomes of 60 Fusarium graminearum, the major fungal pathogen responsible for Fusarium head blight (FHB) in cereal crops world-wide. To investigate adaptive evolution of FHB pathogens, we performed population-level analyses to characterize genomic structure, signatures...

Sensitive Detection of Xanthomonas oryzae Pathovars oryzae and oryzicola by Loop-Mediated Isothermal Amplification

PubMed Central

Lang, Jillian M.; Langlois, Paul; Nguyen, Marian Hanna R.; Triplett, Lindsay R.; Purdie, Laura; Holton, Timothy A.; Djikeng, Appolinaire; Vera Cruz, Casiana M.; Verdier, Valérie

2014-01-01

Molecular diagnostics for crop diseases can enhance food security by enabling the rapid identification of threatening pathogens and providing critical information for the deployment of disease management strategies. Loop-mediated isothermal amplification (LAMP) is a PCR-based tool that allows the rapid, highly specific amplification of target DNA sequences at a single temperature and is thus ideal for field-level diagnosis of plant diseases. We developed primers highly specific for two globally important rice pathogens, Xanthomonas oryzae pv. oryzae, the causal agent of bacterial blight (BB) disease, and X. oryzae pv. oryzicola, the causal agent of bacterial leaf streak disease (BLS), for use in reliable, sensitive LAMP assays. In addition to pathovar distinction, two assays that differentiate X. oryzae pv. oryzae by African or Asian lineage were developed. Using these LAMP primer sets, the presence of each pathogen was detected from DNA and bacterial cells, as well as leaf and seed samples. Thresholds of detection for all assays were consistently 104 to 105 CFU ml−1, while genomic DNA thresholds were between 1 pg and 10 fg. Use of the unique sequences combined with the LAMP assay provides a sensitive, accurate, rapid, simple, and inexpensive protocol to detect both BB and BLS pathogens. PMID:24837384

Earlier occurrence and increased explanatory power of climate for the first incidence of potato late blight caused by Phytophthora infestans in Fennoscandia

PubMed Central

Wiik, Lars; Hannukkala, Asko; Andreasson, Erik; Chen, Deliang; Ou, Tinghai; Liljeroth, Erland; Lankinen, Åsa

2017-01-01

Background Late blight (caused by Phytophthora infestans) is a devastating potato disease that has been found to occur earlier in the season over the last decades in Fennoscandia. Up until now the reasons for this change have not been investigated. Possible explanations for this change are climate alterations, changes in potato production or changes in pathogen biology, such as increased fitness or changes in gene flow within P. infestans populations. The first incidence of late blight is of high economic importance since fungicidal applications should be typically applied two weeks before the first signs of late blight and are repeated on average once a week. Methods We use field observations of first incidence of late blight in experimental potato fields from five sites in Sweden and Finland covering a total of 30 years and investigate whether the earlier incidence of late blight can be related to the climate. Results We linked the field data to meteorological data and found that the previous assumption, used in common late blight models, that the disease only develops at relative humidity levels above 90% had to be rejected. Rather than the typically assumed threshold relationship between late blight disease development and relative humidity we found a linear relationship. Our model furthermore showed two distinct responses of late blight to climate. At the beginning of the observation time (in Sweden until the early 90s and in Finland until the 2000s) the link between climate and first incidence was very weak. However, for the remainder of the time period the link was highly significant, indicating a change in the biological properties of the pathogen which could for example be a change in the dominating reproduction mode or a physiological change in the response of the pathogen to climate. Conclusions The study shows that models used in decision support systems need to be checked and re-parametrized regularly to be able to capture changes in pathogen biology. While this study was performed with data from Fennoscandia this new pathogen biology and late blight might spread to (or already be present at) other parts of the world as well. The strong link between climate and first incidence together with the presented model offers a tool to assess late blight incidence in future climates. PMID:28558041

Earlier occurrence and increased explanatory power of climate for the first incidence of potato late blight caused by Phytophthora infestans in Fennoscandia.

PubMed

Lehsten, Veiko; Wiik, Lars; Hannukkala, Asko; Andreasson, Erik; Chen, Deliang; Ou, Tinghai; Liljeroth, Erland; Lankinen, Åsa; Grenville-Briggs, Laura

2017-01-01

Late blight (caused by Phytophthora infestans) is a devastating potato disease that has been found to occur earlier in the season over the last decades in Fennoscandia. Up until now the reasons for this change have not been investigated. Possible explanations for this change are climate alterations, changes in potato production or changes in pathogen biology, such as increased fitness or changes in gene flow within P. infestans populations. The first incidence of late blight is of high economic importance since fungicidal applications should be typically applied two weeks before the first signs of late blight and are repeated on average once a week. We use field observations of first incidence of late blight in experimental potato fields from five sites in Sweden and Finland covering a total of 30 years and investigate whether the earlier incidence of late blight can be related to the climate. We linked the field data to meteorological data and found that the previous assumption, used in common late blight models, that the disease only develops at relative humidity levels above 90% had to be rejected. Rather than the typically assumed threshold relationship between late blight disease development and relative humidity we found a linear relationship. Our model furthermore showed two distinct responses of late blight to climate. At the beginning of the observation time (in Sweden until the early 90s and in Finland until the 2000s) the link between climate and first incidence was very weak. However, for the remainder of the time period the link was highly significant, indicating a change in the biological properties of the pathogen which could for example be a change in the dominating reproduction mode or a physiological change in the response of the pathogen to climate. The study shows that models used in decision support systems need to be checked and re-parametrized regularly to be able to capture changes in pathogen biology. While this study was performed with data from Fennoscandia this new pathogen biology and late blight might spread to (or already be present at) other parts of the world as well. The strong link between climate and first incidence together with the presented model offers a tool to assess late blight incidence in future climates.

Fire blight disease reactome: RNA-seq transcriptional profile of apple host plant defense responses to Erwinia amylovora pathogen infection.

PubMed

Kamber, Tim; Buchmann, Jan P; Pothier, Joël F; Smits, Theo H M; Wicker, Thomas; Duffy, Brion

2016-02-17

The molecular basis of resistance and susceptibility of host plants to fire blight, a major disease threat to pome fruit production globally, is largely unknown. RNA-sequencing data from challenged and mock-inoculated flowers were analyzed to assess the susceptible response of apple to the fire blight pathogen Erwinia amylovora. In presence of the pathogen 1,080 transcripts were differentially expressed at 48 h post inoculation. These included putative disease resistance, stress, pathogen related, general metabolic, and phytohormone related genes. Reads, mapped to regions on the apple genome where no genes were assigned, were used to identify potential novel genes and open reading frames. To identify transcripts specifically expressed in response to E. amylovora, RT-PCRs were conducted and compared to the expression patterns of the fire blight biocontrol agent Pantoea vagans strain C9-1, another apple pathogen Pseudomonas syringae pv. papulans, and mock inoculated apple flowers. This led to the identification of a peroxidase superfamily gene that was lower expressed in response to E. amylovora suggesting a potential role in the susceptibility response. Overall, this study provides the first transcriptional profile by RNA-seq of the host plant during fire blight disease and insights into the response of susceptible apple plants to E. amylovora.

Fire blight disease reactome: RNA-seq transcriptional profile of apple host plant defense responses to Erwinia amylovora pathogen infection

PubMed Central

Kamber, Tim; Buchmann, Jan P.; Pothier, Joël F.; Smits, Theo H. M.; Wicker, Thomas; Duffy, Brion

2016-01-01

The molecular basis of resistance and susceptibility of host plants to fire blight, a major disease threat to pome fruit production globally, is largely unknown. RNA-sequencing data from challenged and mock-inoculated flowers were analyzed to assess the susceptible response of apple to the fire blight pathogen Erwinia amylovora. In presence of the pathogen 1,080 transcripts were differentially expressed at 48 h post inoculation. These included putative disease resistance, stress, pathogen related, general metabolic, and phytohormone related genes. Reads, mapped to regions on the apple genome where no genes were assigned, were used to identify potential novel genes and open reading frames. To identify transcripts specifically expressed in response to E. amylovora, RT-PCRs were conducted and compared to the expression patterns of the fire blight biocontrol agent Pantoea vagans strain C9-1, another apple pathogen Pseudomonas syringae pv. papulans, and mock inoculated apple flowers. This led to the identification of a peroxidase superfamily gene that was lower expressed in response to E. amylovora suggesting a potential role in the susceptibility response. Overall, this study provides the first transcriptional profile by RNA-seq of the host plant during fire blight disease and insights into the response of susceptible apple plants to E. amylovora. PMID:26883568

PGPR and entomopathogenic fungus bioformulation for the synchronous management of leaffolder pest and sheath blight disease of rice.

PubMed

Karthiba, Loganathan; Saveetha, Kandasamy; Suresh, Seetharaman; Raguchander, Thiruvengadam; Saravanakumar, Duraisamy; Samiyappan, Ramasamy

2010-05-01

The biological control of plant pests and diseases using a single organism has been reported to give inconsistent and poor performance. To improve the efficacy, bioformulations were developed possessing mixtures of bioagents. Bioformulations combining Pseudomonas fluorescens Migula strains Pf1 and AH1 and Beauveria bassiana (Balsamo) Vuill. isolate B2 were developed and tested for their efficacy against leaffolder pest and sheath blight disease on rice under glasshouse and field conditions. The combination of Pf1, AH1 and B2 effectively reduced the incidence of leaffolder insect and sheath blight disease on rice compared with other treatments. An in vitro assay of leaffolder preference to rice leaf tissues treated with Pf1 + AH1 + B2 biformulation showed variation from normal growth and development of leaffolder larvae. Plants treated with the Pf1 + AH1 + B2 combination showed a greater accumulation of enzymes, lipoxygenase and chitinase activity against leaffolder insect compared with other treatments. Similarly, the plants showed a higher accumulation of defence enzymes, peroxidase and polyphenol oxidase activity against sheath blight pathogen in Pf1 + AH1 + B2 treatment compared with the untreated control. The bioformulation mixture attracted the natural enemy population of leaffolder under field conditions. In addition, a significant increase in rice grain yield was observed in Pf1 + AH1 + B2 treatment compared with the untreated control. The combination of P. fluorescens strains and B. bassiana isolate effectively reduced the incidence of leaffolder insect and sheath blight disease on rice plants and showed the possibility of controlling both pest and disease using a single bioformulation.

Pseudomonas blight caused by Pseudomonas syringae on raspberry in California

USDA-ARS?s Scientific Manuscript database

Plantings of red raspberry (Rubus idaeus var. strigosus) exhibited symptoms of a previously undocumented disease. Lesions were observable from both adaxial and abaxial leaf surfaces. As disease progressed, lesions enlarged and coalesced, resulting in significant dark brown to black blighting of the ...

Efficacy of epiphytic bacteria to prevent northern leaf blight caused by Exserohilum turcicum in maize.

PubMed

Sartori, Melina; Nesci, Andrea; García, Julián; Passone, María A; Montemarani, Analía; Etcheverry, Miriam

Eight potential biological control agents (BCAs) were evaluated in planta in order to assess their effectiveness in reducing disease severity of northern leaf blight caused by Exserohilum turcicum. The assay was carried out in greenhouse. Twenty-six-day-old plants, V4 phenological stage, were inoculated with antagonists by foliar spray. Only one biocontrol agent was used per treatment. Ten days after this procedure, all treatments were inoculated with E. turcicum by foliar application. Treatments performed were: C-Et: control of E. turcicum; T1: isolate 1 (Enterococcus genus)+E. turcicum; T2: isolate 2 (Corynebacterium genus)+E. turcicum; T3: isolate 3 (Pantoea genus)+E. turcicum; T4: isolate 4 (Corynebacterium genus)+E. turcicum; T5: isolate 5 (Pantoea genus)+E. turcicum; T6: isolate 6 (Bacillus genus)+E. turcicum; T7: isolate 7 (Bacillus genus)+E. turcicum; T8: isolate 8 (Bacillus genus)+E. turcicum. Monitoring of antagonists on the phyllosphere was performed at different times. Furthermore, the percentage of infected leaves and, plant and leaf incidence were determined. Foliar application of different bacteria significantly reduced the leaf blight between 30-78% and 39-56% at 20 and 39 days respectively. It was observed that in the V10 stage of maize plants, isolate 8 (Bacillus spp.) caused the greatest effect on reducing the severity of northern leaf blight. Moreover, isolate 8 was the potential BCA that showed more stability in the phyllosphere. At 39 days, all potential biocontrol agents had a significant effect on controlling the disease caused by E. turcicum. Copyright © 2016 Asociación Argentina de Microbiología. Publicado por Elsevier España, S.L.U. All rights reserved.

Comprehensive analysis of microRNA-Seq and target mRNAs of rice sheath blight pathogen provides new insights into pathogenic regulatory mechanisms.

PubMed

Lin, Runmao; He, Liye; He, Jiayu; Qin, Peigang; Wang, Yanran; Deng, Qiming; Yang, Xiaoting; Li, Shuangcheng; Wang, Shiquan; Wang, Wenming; Liu, Huainian; Li, Ping; Zheng, Aiping

2016-07-03

MicroRNAs (miRNAs) are ∼22 nucleotide non-coding RNAs that regulate gene expression by targeting mRNAs for degradation or inhibiting protein translation. To investigate whether miRNAs regulate the pathogenesis in necrotrophic fungus Rhizoctonia solani AG1 IA, which causes significant yield loss in main economically important crops, and to determine the regulatory mechanism occurring during pathogenesis, we constructed hyphal small RNA libraries from six different infection periods of the rice leaf. Through sequencing and analysis, 177 miRNA-like small RNAs (milRNAs) were identified, including 15 candidate pathogenic novel milRNAs predicted by functional annotations of their target mRNAs and expression patterns of milRNAs and mRNAs during infection. Reverse transcription-quantitative polymerase chain reaction results for randomly selected milRNAs demonstrated that our novel comprehensive predictions had a high level of accuracy. In our predicted pathogenic protein-protein interaction network of R. solani, we added the related regulatory milRNAs of these core coding genes into the network, and could understand the relationships among these regulatory factors more clearly at the systems level. Furthermore, the putative pathogenic Rhi-milR-16, which negatively regulates target gene expression, was experimentally validated to have regulatory functions by a dual-luciferase reporter assay. Additionally, 23 candidate rice miRNAs that may involve in plant immunity against R. solani were discovered. This first study on novel pathogenic milRNAs of R. solani AG1 IA and the recognition of target genes involved in pathogenicity, as well as rice miRNAs, participated in defence against R. solani could provide new insights into revealing the pathogenic mechanisms of the severe rice sheath blight disease. © The Author 2016. Published by Oxford University Press on behalf of Kazusa DNA Research Institute.

Identification of an emergent bacterial blight of garlic in Brazil

USDA-ARS?s Scientific Manuscript database

Outbreaks of a bacterial blight disease occurred on garlic (Allium sativum) cultivars Roxo Caxiense, Quiteria and Cacador in Southern Brazil, and threatened the main production regions of Rio Grande do Sul State. Symptoms were characterized by watersoaked reddish streaks along the leaf midrib, follo...

75 FR 57019 - Pesticide Product Registrations; Conditional Approval

Federal Register 2010, 2011, 2012, 2013, 2014

2010-09-17

... foliar use on soybeans to control brown spot, cercospora blight, frogeye leaf spot, leaf spot, powdery..., 2010. G. Jeffrey Herndon, Acting Director, Registration Division, Office of Pesticide Programs. [FR Doc...

[Erwinia amylovora--the fire blight pathogen of trees in Ukraine].

PubMed

Iakovleva, L M; Moroz, S N; Shcherbina, T N; Ogorodnik, L E; Gvozdiak, R I; Patyka, V F

2014-01-01

Niduses of fire blight of fruit and ornamental trees have been found in the Kyiv and Vinnitsa regions of Ukraine. Pathogen Erwinia amylovora was isolated between April and October. The pathogen was often accompanied by bacteria Pseudomonas syringae pv. syringae. Artificial infection with a mixture of bacteria E. amylovora and P. syringae pv. syringae accelerates and enhances the disease process in the laboratory.

Introduction to Oomycetes

USDA-ARS?s Scientific Manuscript database

The oomycetes, also known as “water molds”, are a group of several hundred organisms that include some of the most devastating plant pathogens. The diseases they cause include seedling blights, damping-off, root rots, foliar blights and downy mildews. Some notable diseases are the late blight of po...

Use of mycelium and detached leaves in bioassays for assessing resistance to boxwood blight

USDA-ARS?s Scientific Manuscript database

Boxwood blight caused by Calonectria pseudonaviculata is a newly emergent disease of boxwood (Buxus L.) in the United States that causes leaf drop, stem lesions, and plant death. A rapid and reliable laboratory assay that enables screening hundreds of boxwood genotypes for resistance to boxwood blig...

Suppression of the rice fatty-acid desaturase gene OsSSI2 enhances resistance to blast and leaf blight diseases in rice.

PubMed

Jiang, Chang-Jie; Shimono, Masaki; Maeda, Satoru; Inoue, Haruhiko; Mori, Masaki; Hasegawa, Morifumi; Sugano, Shoji; Takatsuji, Hiroshi

2009-07-01

Fatty acids and their derivatives play important signaling roles in plant defense responses. It has been shown that suppressing a gene for stearoyl acyl carrier protein fatty-acid desaturase (SACPD) enhances the resistance of Arabidopsis (SSI2) and soybean to multiple pathogens. In this study, we present functional analyses of a rice homolog of SSI2 (OsSSI2) in disease resistance of rice plants. A transposon insertion mutation (Osssi2-Tos17) and RNAi-mediated knockdown of OsSSI2 (OsSSI2-kd) reduced the oleic acid (18:1) level and increased that of stearic acid (18:0), indicating that OsSSI2 is responsible for fatty-acid desaturase activity. These plants displayed spontaneous lesion formation in leaf blades, retarded growth, slight increase in endogenous free salicylic acid (SA) levels, and SA/benzothiadiazole (BTH)-specific inducible genes, including WRKY45, a key regulator of SA/BTH-induced resistance, in rice. Moreover, the OsSSI2-kd plants showed markedly enhanced resistance to the blast fungus Magnaporthe grisea and leaf-blight bacteria Xanthomonas oryzae pv. oryzae. These results suggest that OsSSI2 is involved in the negative regulation of defense responses in rice, as are its Arabidopsis and soybean counterparts. Microarray analyses identified 406 genes that were differentially expressed (>or=2-fold) in OsSSI2-kd rice plants compared with wild-type rice and, of these, approximately 39% were BTH responsive. Taken together, our results suggest that induction of SA-responsive genes, including WRKY45, is likely responsible for enhanced disease resistance in OsSSI2-kd rice plants.

Characterization of the bacterial stem blight pathogen of alfalfa, Pseudomonas syringae pv. syringae ALF3

USDA-ARS?s Scientific Manuscript database

Bacterial stem blight of alfalfa occurs sporadically in the central and western U.S. Yield losses of up to 50% of the first harvest can occur with some cultivars. Developing resistant cultivars is hampered by lack of information on the pathogen and a standard test for evaluating plant germplasm. Bac...

Control of fire blight by Pseudomonas fluorescens A506 and Pantoea vagans C9-1 applied as single strains and mixed inocula

USDA-ARS?s Scientific Manuscript database

The biological control agents Pseudomonas fluorescens A506 and Pantoea vagans C9-1 were evaluated individually and in combination for the suppression of fire blight of pear or apple in ten field trials inoculated with the pathogen Erwinia amylovora. The formulation of pathogen inoculum applied to b...

Complete Genome Sequence of Pseudomonas fluorescens LBUM636, a Strain with Biocontrol Capabilities against Late Blight of Potato

PubMed Central

Morrison, Christopher K.; Novinscak, Amy; Gadkar, Vijay J.; Joly, David L.

2016-01-01

Herein provided is the full-genome sequence of Pseudomonas fluorescens LBUM636. This strain is a plant growth-promoting rhizobacterium (PGPR) which produces phenazine-1-carboxylic acid, an antibiotic involved in the biocontrol of numerous plant pathogens, including late blight of potato caused by the plant pathogen Phytophthora infestans. PMID:27231373

Association between QTLs and morphological traits toward sheath blight resistance in rice (Oryza sativa L.)

PubMed Central

Hossain, Md Kamal; Jena, Kshirod Kumar; Bhuiyan, Md Atiqur Rahman; Wickneswari, Ratnam

2016-01-01

Sheath blight is considered the most significant disease of rice and causes enormous yield losses over the world. Breeding for resistant varieties is the only viable option to combat the disease efficiently. Seventeen diverged rice genotypes along with 17 QTL-linked SSR markers were evaluated under greenhouse conditions. Pearson’s correlation showed only the flag leaf angle had a significant correlation with sheath blight resistance under greenhouse screening. Multivariate analysis based on UPGMA clustering and principal component analysis (PCA) indicated that the flag leaf angle, flag leaf length, and plant compactness were significantly associated with the following SSR marker alleles: RM209 (116,130), RM202 (176), RM224 (126), RM257 (156), RM426 (175), and RM6971 (196), which are linked to the SB QTLs: QRlh11, qSBR11-3, qSBR11-1, qSBR9-1, qShB3-2, and qSB-9. A Mantel test suggested a weak relationship between the observed phenotypes and allelic variation patterns, implying the independent nature of morphological and molecular variations. Teqing and Tetep were found to be the most resistant cultivars. IR65482-4-136-2-2, MR219-4, and MR264 showed improved resistance potentials. These results suggest that the morphological traits and QTLs which have been found to associate with sheath blight resistance are a good choice to enhance resistance through pyramiding either 2 QTLs or QTLs and traits in susceptible rice cultivars. PMID:27795687

Lack of a Cytoplasmic RLK, Required for ROS Homeostasis, Induces Strong Resistance to Bacterial Leaf Blight in Rice.

PubMed

Yoo, Youngchul; Park, Jong-Chan; Cho, Man-Ho; Yang, Jungil; Kim, Chi-Yeol; Jung, Ki-Hong; Jeon, Jong-Seong; An, Gynheung; Lee, Sang-Won

2018-01-01

Many scientific findings have been reported on the beneficial function of reactive oxygen species (ROS) in various cellular processes, showing that they are not just toxic byproducts. The double-edged role of ROS shows the importance of the regulation of ROS level. We report a gene, rrsRLK (required for ROS-scavenging receptor-like kinase), that encodes a cytoplasmic RLK belonging to the non-RD kinase family. The gene was identified by screening rice RLK mutant lines infected with Xanthomonas oryzae pv. oryzae ( Xoo ), an agent of bacterial leaf blight of rice. The mutant (Δ rrsRLK ) lacking the Os01g02290 gene was strongly resistant to many Xoo strains, but not to the fungal pathogen Magnaporthe grisea . Δ rrsRLK showed significantly higher expression of OsPR1a , OsPR1b , OsLOX , RBBTI4 , and jasmonic acid-related genes than wild type. We showed that rrsRLK protein interacts with OsVOZ1 (vascular one zinc-finger 1) and OsPEX11 (peroxisomal biogenesis factor 11). In the further experiments, abnormal biogenesis of peroxisomes, hydrogen peroxide (H 2 O 2 ) accumulation, and reduction of activity of ROS-scavenging enzymes were investigated in Δ rrsRLK . These results suggest that the enhanced resistance in Δ rrsRLK is due to H 2 O 2 accumulation caused by irregular ROS-scavenging mechanism, and rrsRLK is most likely a key regulator required for ROS homeostasis in rice.

Global invasive Cochliobolus species: cohort of destroyers with implications in food losses and insecurity in the twenty-first century.

PubMed

Bengyella, Louis; Yekwa, Elsie Laban; Nawaz, Kiran; Iftikhar, Sehrish; Tambo, Ernest; Alisoltani, Arghavan; Feto, Naser Aliye; Roy, Pranab

2018-01-01

Matching the global food demand by 2050 and to ensure the stability of food security in over than 99 countries, it is necessary to scale up the production of food such as sorghum, wheat, rice, maize and sugarcane which are however natural hosts of Cochliobolus species. Cochliobolus species major epidemics such as the Great Bengal famine, Southern corn leaf blight, and Northern leaf spot blight were associated with substantial economic losses in the past decades. Thus, there is an urgent need to establish a specific coordinated global surveillance program for the migration of invasive Cochliobolus species, planning contextual control programs engaging all agricultural stakeholders and information sharing in real time for prevention of disastrous Cochliobolus disease outbreak effects. We discuss pertinent outcome of interactions of cash crops with Cochliobolus species having devastating impact on the livelihood of farmers and food security. While post-genomic era elucidated prominent differences among Cochliobolus heterostrophus, C. carbonum, C. victoriae, C. lunatus and C. miyabeanus, their destructive potentials and implications in food losses remained unearthed. Intriguingly, the annual colossal losses caused by Cochliobolus species in the production perspective of sorghum, wheat, rice, maize, cassava and soybean is estimated over 10 billion USD worldwide. This paper provides a comprehensive analysis of the invasive Cochliobolus species distribution and diversity, evolving pathogenicity, persistent diseases, threats and epidemics, consequences on food crops production and increasing global food insecurity issues.

Putative resistance gene markers associated with quantitative trait loci for fire blight resistance in Malus 'Robusta 5' accessions

USDA-ARS?s Scientific Manuscript database

Breeding of fire blight resistant scions and rootstocks is a goal of several international apple breeding programs, as options are limited for management of this destructive disease caused by the bacterial pathogen Erwinia amylovora. A broad, large effect QTL for fire blight resistance has been pre...

Chitosan-induced immunity in Camellia sinensis (L.) O. Kuntze against blister blight disease is mediated by nitric-oxide.

PubMed

Chandra, Swarnendu; Chakraborty, Nilanjan; Panda, Koustubh; Acharya, Krishnendu

2017-06-01

Blister blight disease, caused by an obligate biotrophic fungal pathogen, Exobasidium vexans Massee is posing a serious threat for tea cultivation in Asia. As the use of chemical pesticides on tea leaves substantially increases the toxic risks of tea consumption, serious attempts are being made to control such pathogens by boosting the intrinsic natural defense responses against invading pathogens in tea plants. In this study, the nature and durability of resistance offered by chitosan and the possible mechanism of chitosan-induced defense induction in Camellia sinensis (L.) O. Kuntze plants against blister blight disease were investigated. Foliar application of 0.01% chitosan solution at 15 days interval not only reduced the blister blight incidence for two seasons, but also maintained the induced expressions of different defense related enzymes and total phenol content compared to the control. Defense responses induced by chitosan were found to be down regulated under nitric oxide (NO) deficient conditions in vivo, indicating that the observed chitosan-induced resistance is probably activated via NO signaling. Such role of NO in host defense response was further established by application of the NO donor, sodium nitroprusside (SNP), which produced similar defense responses accomplished through chitosan treatment. Taken together, our results suggest that increased production of NO in chitosan-treated tea plants may play a critical role in triggering the innate defense responses effective against plant pathogens, including that causing the blister blight disease. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

Biocontrol of Bacterial Leaf Blight of Rice and Profiling of Secondary Metabolites Produced by Rhizospheric Pseudomonas aeruginosa BRp3

PubMed Central

Yasmin, Sumera; Hafeez, Fauzia Y.; Mirza, Muhammad S.; Rasul, Maria; Arshad, Hafiz M. I.; Zubair, Muhammad; Iqbal, Mazhar

2017-01-01

Xanthomonas oryzae pv. oryzae (Xoo) is widely prevalent and causes Bacterial Leaf Blight (BLB) in Basmati rice grown in different areas of Pakistan. There is a need to use environmentally safe approaches to overcome the loss of grain yield in rice due to this disease. The present study aimed to develop inocula, based on native antagonistic bacteria for biocontrol of BLB and to increase the yield of Super Basmati rice variety. Out of 512 bacteria isolated from the rice rhizosphere and screened for plant growth promoting determinants, the isolate BRp3 was found to be the best as it solubilized 97 μg/ mL phosphorus, produced 30 μg/mL phytohormone indole acetic acid and 15 mg/ L siderophores in vitro. The isolate BRp3 was found to be a Pseudomonas aeruginosa based on 16S rRNA gene sequencing (accession no. HQ840693). This bacterium showed antagonism in vitro against different phytopathogens including Xoo and Fusarium spp. Strain BRp3 showed consistent pathogen suppression of different strains of BLB pathogen in rice. Mass spectrometric analysis detected the production of siderophores (1-hydroxy-phenazine, pyocyanin, and pyochellin), rhamnolipids and a series of already characterized 4-hydroxy-2-alkylquinolines (HAQs) as well as novel 2,3,4-trihydroxy-2-alkylquinolines and 1,2,3,4-tetrahydroxy-2-alkylquinolines in crude extract of BRp3. These secondary metabolites might be responsible for the profound antibacterial activity of BRp3 against Xoo pathogen. Another contributing factor toward the suppression of the pathogen was the induction of defense related enzymes in the rice plant by the inoculated strain BRp3. When used as an inoculant in a field trial, this strain enhanced the grain and straw yields by 51 and 55%, respectively, over non-inoculated control. Confocal Laser Scanning Microscopy (CLSM) used in combination with immunofluorescence marker confirmed P. aeruginosa BRp3 in the rice rhizosphere under sterilized as well as field conditions. The results provide evidence that novel secondary metabolites produced by BRp3 may contribute to its activity as a biological control agent against Xoo and its potential to promote the growth and yield of Super Basmati rice. PMID:29018437

Using Citrus aurantifolia essential oil for the potential biocontrol of Colocasia esculenta (taro) leaf blight caused by Phytophthora colocasiae.

PubMed

Tchameni, Séverin Nguemezi; Mbiakeu, Staelle Njamou; Sameza, Modeste Lambert; Jazet, Pierre Michel Dongmo; Tchoumbougnang, François

2017-11-17

The aim of this work was to evaluate the antimicrobial activities of leaves and epicarp of Citrus aurantifolia essential oil against Phytophthora colocasiae, the causative agent of taro leaf blight. Oils were extracted by hydrodistillation, and their chemical composition was determined by gas chromatography and gas chromatography coupled with mass spectrometry. Antimicrobial activities of oils were tested in vitro against mycelium growth and sporangium production. In situ tests were done on healthy taro leaves, and the necrosis symptoms were evaluated. Results showed that the essential oil extraction yields from leaves and epicarp were 0.61 and 0.36%, respectively. Limonene (48.96%), bornyl acetate (14.18%), geraniol (10.53%), geranial (3.93%), and myrcene (3.14%) were the main components in leaf oil, while limonene (59.09%), cis-hydrate sabinene (7.53%), geranial (5.61%), myrtenol (5.02%), and terpinen-4-ol (3.48%) were the main components in epicarp oil. Both oils exhibited antimicrobial activities with total inhibition of the mycelium growth at 500 and 900 ppm for leaf and epicarp, respectively. The highest inhibitory concentration of sporangium production was 400 (72.84%) and 800 ppm (80.65%) for leaf and epicarp oil, respectively. For the standard fungicide (metalaxyl), the total inhibition value of mycelial growth and sporangium production was 750 ppm. In situ tests showed that, at 5000 ppm, total inhibition (100%) was obtained for a preventive test, while 50% of the inhibition was observed for a curative test when leaf oil was applied. When epicarp essential oil was applied at 5000 ppm, 47.5 and 16.66% of the reduction of leaf necrosis were observed for the preventive and curative test, respectively. There were positive correlations between both the oil concentration and the reduction of necrosis caused by P. colocasiae. These findings suggest that the C. aurantifolia essential oil could serve as an eco-friendly biocontrol for the management of taro leaf blight.

Molecular genetics of Erwinia amylovora involved in the development of fire blight.

PubMed

Oh, Chang-Sik; Beer, Steven V

2005-12-15

The bacterial plant pathogen, Erwinia amylovora, causes the devastating disease known as fire blight in some Rosaceous plants like apple, pear, quince, raspberry and several ornamentals. Knowledge of the factors affecting the development of fire blight has mushroomed in the last quarter century. On the molecular level, genes encoding a Hrp type III secretion system, genes encoding enzymes involved in synthesis of extracellular polysaccharides and genes facilitating the growth of E. amylovora in its host plants have been characterized. The Hrp pathogenicity island, delimited by genes suggesting horizontal gene transfer, is composed of four distinct regions, the hrp/hrc region, the HEE (Hrp effectors and elicitors) region, the HAE (Hrp-associated enzymes) region, and the IT (Island transfer) region. The Hrp pathogenicity island encodes a Hrp type III secretion system (TTSS), which delivers several proteins from bacteria to plant apoplasts or cytoplasm. E. amylovora produces two exopolysaccharides, amylovoran and levan, which cause the characteristic fire blight wilting symptom in host plants. In addition, other genes, and their encoded proteins, have been characterized as virulence factors of E. amylovora that encode enzymes facilitating sorbitol metabolism, proteolytic activity and iron harvesting. This review summarizes our understanding of the genes and gene products of E. amylovora that are involved in the development of the fire blight disease.

Cutinase in Cryphonectria parasitica, the chestnut blight fungus: suppression of cutinase gene expression in isogenic hypovirulent strains containing double-stranded RNAs

Treesearch

D.A. ​Varley; G.K. Podila; S.T. Hiremath

1992-01-01

Plant-pathogenic fungi produce cutinase, an enzyme required to degrade plant cuticles and facilitate penetration into the host. The absence of cutinase or a decrease in its production has been associated with a decrease in pathogenicity of the fungus. A set of isogenic strains of Cryphonectria parasitica, the chestnut blight fungus, was tested for...

Medfly Ceratitis capitata as Potential Vector for Fire Blight Pathogen Erwinia amylovora: Survival and Transmission.

PubMed

Ordax, Mónica; Piquer-Salcedo, Jaime E; Santander, Ricardo D; Sabater-Muñoz, Beatriz; Biosca, Elena G; López, María M; Marco-Noales, Ester

2015-01-01

Monitoring the ability of bacterial plant pathogens to survive in insects is required for elucidating unknown aspects of their epidemiology and for designing appropriate control strategies. Erwinia amylovora is a plant pathogenic bacterium that causes fire blight, a devastating disease in apple and pear commercial orchards. Studies on fire blight spread by insects have mainly focused on pollinating agents, such as honeybees. However, the Mediterranean fruit fly (medfly) Ceratitis capitata (Diptera: Tephritidae), one of the most damaging fruit pests worldwide, is also common in pome fruit orchards. The main objective of the study was to investigate whether E. amylovora can survive and be transmitted by the medfly. Our experimental results show: i) E. amylovora can survive for at least 8 days inside the digestive tract of the medfly and until 28 days on its external surface, and ii) medflies are able to transmit the bacteria from inoculated apples to both detached shoots and pear plants, being the pathogen recovered from lesions in both cases. This is the first report on E. amylovora internalization and survival in/on C. capitata, as well as the experimental transmission of the fire blight pathogen by this insect. Our results suggest that medfly can act as a potential vector for E. amylovora, and expand our knowledge on the possible role of these and other insects in its life cycle.

Medfly Ceratitis capitata as Potential Vector for Fire Blight Pathogen Erwinia amylovora: Survival and Transmission

PubMed Central

Ordax, Mónica; Piquer-Salcedo, Jaime E.; Santander, Ricardo D.; Sabater-Muñoz, Beatriz; Biosca, Elena G.; López, María M.; Marco-Noales, Ester

2015-01-01

Monitoring the ability of bacterial plant pathogens to survive in insects is required for elucidating unknown aspects of their epidemiology and for designing appropriate control strategies. Erwinia amylovora is a plant pathogenic bacterium that causes fire blight, a devastating disease in apple and pear commercial orchards. Studies on fire blight spread by insects have mainly focused on pollinating agents, such as honeybees. However, the Mediterranean fruit fly (medfly) Ceratitis capitata (Diptera: Tephritidae), one of the most damaging fruit pests worldwide, is also common in pome fruit orchards. The main objective of the study was to investigate whether E. amylovora can survive and be transmitted by the medfly. Our experimental results show: i) E. amylovora can survive for at least 8 days inside the digestive tract of the medfly and until 28 days on its external surface, and ii) medflies are able to transmit the bacteria from inoculated apples to both detached shoots and pear plants, being the pathogen recovered from lesions in both cases. This is the first report on E. amylovora internalization and survival in/on C. capitata, as well as the experimental transmission of the fire blight pathogen by this insect. Our results suggest that medfly can act as a potential vector for E. amylovora, and expand our knowledge on the possible role of these and other insects in its life cycle. PMID:25978369

Data Mining Feature Subset Weighting and Selection Using Genetic Algorithms

DTIC Science & Technology

2002-03-01

seed-stain, anthracnose, phyllosticta-leaf-spot, alternarialeaf-spot, frog-eye-leaf- spot, diaporthe-pod-&-stem-blight, cyst - nematode , 2-4-d-injury...seed-discolor: absent,present,?. 33. seed-size: norm,lt-norm,?. 34. shriveling: absent,present,?. 35. roots: norm,rotted,galls- cysts

Overexpression of BSR1 confers broad-spectrum resistance against two bacterial diseases and two major fungal diseases in rice

PubMed Central

Maeda, Satoru; Hayashi, Nagao; Sasaya, Takahide; Mori, Masaki

2016-01-01

Broad-spectrum disease resistance against two or more types of pathogen species is desirable for crop improvement. In rice, Xanthomonas oryzae pv. oryzae (Xoo), the causal bacteria of rice leaf blight, and Magnaporthe oryzae, the fungal pathogen causing rice blast, are two of the most devastating pathogens. We identified the rice BROAD-SPECTRUM RESISTANCE 1 (BSR1) gene for a BIK1-like receptor-like cytoplasmic kinase using the FOX hunting system, and demonstrated that BSR1-overexpressing (OX) rice showed strong resistance to the bacterial pathogen, Xoo and the fungal pathogen, M. oryzae. Here, we report that BSR1-OX rice showed extended resistance against two other different races of Xoo, and to at least one other race of M. oryzae. In addition, the rice showed resistance to another bacterial species, Burkholderia glumae, which causes bacterial seedling rot and bacterial grain rot, and to Cochliobolus miyabeanus, another fungal species causing brown spot. Furthermore, BSR1-OX rice showed slight resistance to rice stripe disease, a major viral disease caused by rice stripe virus. Thus, we demonstrated that BSR1-OX rice shows remarkable broad-spectrum resistance to at least two major bacterial species and two major fungal species, and slight resistance to one viral pathogen. PMID:27436950

Overexpression of BSR1 confers broad-spectrum resistance against two bacterial diseases and two major fungal diseases in rice.

PubMed

Maeda, Satoru; Hayashi, Nagao; Sasaya, Takahide; Mori, Masaki

2016-06-01

Broad-spectrum disease resistance against two or more types of pathogen species is desirable for crop improvement. In rice, Xanthomonas oryzae pv. oryzae (Xoo), the causal bacteria of rice leaf blight, and Magnaporthe oryzae, the fungal pathogen causing rice blast, are two of the most devastating pathogens. We identified the rice BROAD-SPECTRUM RESISTANCE 1 (BSR1) gene for a BIK1-like receptor-like cytoplasmic kinase using the FOX hunting system, and demonstrated that BSR1-overexpressing (OX) rice showed strong resistance to the bacterial pathogen, Xoo and the fungal pathogen, M. oryzae. Here, we report that BSR1-OX rice showed extended resistance against two other different races of Xoo, and to at least one other race of M. oryzae. In addition, the rice showed resistance to another bacterial species, Burkholderia glumae, which causes bacterial seedling rot and bacterial grain rot, and to Cochliobolus miyabeanus, another fungal species causing brown spot. Furthermore, BSR1-OX rice showed slight resistance to rice stripe disease, a major viral disease caused by rice stripe virus. Thus, we demonstrated that BSR1-OX rice shows remarkable broad-spectrum resistance to at least two major bacterial species and two major fungal species, and slight resistance to one viral pathogen.

Characterization of rhizosphere bacteria for control of phytopathogenic fungi of tomato.

PubMed

Pastor, Nicolás; Carlier, Evelin; Andrés, Javier; Rosas, Susana B; Rovera, Marisa

2012-03-01

Fluorescent Pseudomonas spp., isolated from rhizosphere soil of tomato and pepper plants, were evaluated in vitro as potential antagonists of fungal pathogens. Strains were characterized using the API 20NE biochemical system, and tested against the causal agents of stem canker and leaf blight (Alternaria alternata f. sp. lycopersici), southern blight (Sclerotium rolfsii Sacc.), and root rot (Fusarium solani). To this end, dual culture antagonism assays were carried out on 25% Tryptic Soy Agar, King B medium, and Potato Dextrose Agar to determine the effect of the strains on mycelial growth of the pathogens. The effect of two concentrations of FeCl(3) on antagonism against Alternaria alternata f. sp. lycopersici was also tested. In addition, strains were screened for ability to produce exoenzymes and siderophores. Finally, the selected Pseudomonas strain, PCI2, was evaluated for effect on tomato seedling development and as a potential candidate for controlling tomato damping-off caused by Sclerotium rolfsii Sacc., under growth chamber conditions. All strains significantly inhibited Alternaria alternata f. sp. lycopersici, particularly in 25% TSA medium. Antagonistic effect on Sclerotium rolfsii Sacc. and Fusarium solani was greater on King B medium. Protease was produced by 30% of the strains, but no strains produced cellulase or chitinase. Growth chamber studies resulted in significant increases in plant stand as well as in root dry weight. PCI2 was able to establish and survive in tomato plants rhizosphere after 40 days following planting of bacterized seeds. Copyright © 2011 Elsevier Ltd. All rights reserved.

Evaluation of Different PCR-Based Assays and LAMP Method for Rapid Detection of Phytophthora infestans by Targeting the Ypt1 Gene

PubMed Central

Khan, Mehran; Li, Benjin; Jiang, Yue; Weng, Qiyong; Chen, Qinghe

2017-01-01

Late blight, caused by the oomycete Phytophthora infestans, is one of the most devastating diseases affecting potato and tomato worldwide. Early diagnosis of the P. infestans pathogen causing late blight should be the top priority for addressing disease epidemics and management. In this study, we performed a loop-mediated isothermal amplification (LAMP) assay, conventional polymerase chain reaction (PCR), nested PCR, and real-time PCR to verify and compare the sensitivity and specificity of the reaction based on the Ypt1 (Ras-related protein) gene of P. infestans. In comparison with the PCR-based assays, the LAMP technique led to higher specificity and sensitivity, using uncomplicated equipment with an equivalent time frame. All 43 P. infestans isolates, yielded positive detection results using LAMP assay showing no cross reaction with other Phytophthora spp., oomycetes or fungal pathogens. The LAMP assay yielded the lowest detectable DNA concentration (1.28 × 10-4 ng μL-1), being 10 times more sensitive than nested PCR (1.28 × 10-3 ng μL-1), 100 times more sensitive than real-time PCR (1.28 × 10-2 ng μL-1) and 103 times more sensitive than the conventional PCR assay (1.28 × 10-1 ng μL-1). In the field experiment, the LAMP assay outperformed the other tests by amplifying only diseased tissues (leaf and stem), and showing no positive reaction in healthy tissues. Overall, the LAMP assay developed in this study provides a specific, sensitive, simple, and effective visual method for detection of the P. infestans pathogen, and is therefore suitable for application in early prediction of the disease to reduce the risk of epidemics. PMID:29051751

AraC/XylS Family Stress Response Regulators Rob, SoxS, PliA, and OpiA in the Fire Blight Pathogen Erwinia amylovora

PubMed Central

Pletzer, Daniel; Schweizer, Gabriel

2014-01-01

Transcriptional regulators of the AraC/XylS family have been associated with multidrug resistance, organic solvent tolerance, oxidative stress, and virulence in clinically relevant enterobacteria. In the present study, we identified four homologous AraC/XylS regulators, Rob, SoxS, PliA, and OpiA, from the fire blight pathogen Erwinia amylovora Ea1189. Previous studies have shown that the regulators MarA, Rob, and SoxS from Escherichia coli mediate multiple-antibiotic resistance, primarily by upregulating the AcrAB-TolC efflux system. However, none of the four AraC/XylS regulators from E. amylovora was able to induce a multidrug resistance phenotype in the plant pathogen. Overexpression of rob led to a 2-fold increased expression of the acrA gene. However, the rob-overexpressing strain showed increased resistance to only a limited number of antibiotics. Furthermore, Rob was able to induce tolerance to organic solvents in E. amylovora by mechanisms other than efflux. We demonstrated that SoxS from E. amylovora is involved in superoxide resistance. A soxS-deficient mutant of Ea1189 was not able to grow on agar plates supplemented with the superoxide-generating agent paraquat. Furthermore, expression of soxS was induced by redox cycling agents. We identified two novel members of the AraC/XylS family in E. amylovora. PliA was highly upregulated during the early infection phase in apple rootstock and immature pear fruits. Multiple compounds were able to induce the expression of pliA, including apple leaf extracts, phenolic compounds, redox cycling agents, heavy metals, and decanoate. OpiA was shown to play a role in the regulation of osmotic and alkaline pH stress responses. PMID:24936054

Evaluation of Different PCR-Based Assays and LAMP Method for Rapid Detection of Phytophthora infestans by Targeting the Ypt1 Gene.

PubMed

Khan, Mehran; Li, Benjin; Jiang, Yue; Weng, Qiyong; Chen, Qinghe

2017-01-01

Late blight, caused by the oomycete Phytophthora infestans , is one of the most devastating diseases affecting potato and tomato worldwide. Early diagnosis of the P. infestans pathogen causing late blight should be the top priority for addressing disease epidemics and management. In this study, we performed a loop-mediated isothermal amplification (LAMP) assay, conventional polymerase chain reaction (PCR), nested PCR, and real-time PCR to verify and compare the sensitivity and specificity of the reaction based on the Ypt1 (Ras-related protein) gene of P. infestans. In comparison with the PCR-based assays, the LAMP technique led to higher specificity and sensitivity, using uncomplicated equipment with an equivalent time frame. All 43 P. infestans isolates, yielded positive detection results using LAMP assay showing no cross reaction with other Phytophthora spp., oomycetes or fungal pathogens. The LAMP assay yielded the lowest detectable DNA concentration (1.28 × 10 -4 ng μL -1 ), being 10 times more sensitive than nested PCR (1.28 × 10 -3 ng μL -1 ), 100 times more sensitive than real-time PCR (1.28 × 10 -2 ng μL -1 ) and 10 3 times more sensitive than the conventional PCR assay (1.28 × 10 -1 ng μL -1 ). In the field experiment, the LAMP assay outperformed the other tests by amplifying only diseased tissues (leaf and stem), and showing no positive reaction in healthy tissues. Overall, the LAMP assay developed in this study provides a specific, sensitive, simple, and effective visual method for detection of the P. infestans pathogen, and is therefore suitable for application in early prediction of the disease to reduce the risk of epidemics.

Monitoring Phytophthora ramorum in soil, leaf litter, rain traps, and watercourses in an historical cornish garden

Treesearch

David Lockley; Judith Turner; Gillian Humphries; Phil Jennings

2008-01-01

Phytophthora ramorum was identified as the cause of a leaf blight on rhododendrons in an historic garden in Cornwall in 2003. A programme of measures was set in place to eradicate the disease from the garden and several sites were selected to monitor the effect of these measures on the recovery of P. ramorum from soil, leaf litter...

Harnessing the microbiome to reduce Fusarium head blight

USDA-ARS?s Scientific Manuscript database

Fusarium graminearum (Fg), the primary fungal pathogen responsible for Fusarium head blight (FHB), reduces crop yield and contaminates grain with trichothecene mycotoxins that are deleterious to plant, human and animal health. In this presentation, we will discuss two different research projects tha...

Edge effects, not connectivity, determine the incidence and development of a foliar fungal plant disease.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Johnson, Brenda, L.; Haddad, Nick, M.

2011-08-01

Using a model plant-pathogen system in a large-scale habitat corridor experiment, we found that corridors do not facilitate the movement of wind-dispersed plant pathogens, that connectivity of patches does not enhance levels of foliar fungal plant disease, and that edge effects are the key drivers of plant disease dynamics. Increased spread of infectious disease is often cited as a potential negative effect of habitat corridors used in conservation, but the impacts of corridors on pathogen movement have never been tested empirically. Using sweet corn (Zea mays) and southern corn leaf blight (Cochliobolus heterostrophus) as a model plant-pathogen system, we testedmore » the impacts of connectivity and habitat fragmentation on pathogen movement and disease development at the Savannah River Site, South Carolina, USA. Over time, less edgy patches had higher proportions of diseased plants, and distance of host plants to habitat edges was the greatest determinant of disease development. Variation in average daytime temperatures provided a possible mechanism for these disease patterns. Our results show that worries over the potentially harmful effects of conservation corridors on disease dynamics are misplaced, and that, in a conservation context, many diseases can be better managed by mitigating edge effects.« less

Fire blight: applied genomic insights of the pathogen and host

USDA-ARS?s Scientific Manuscript database

The enterobacterial phytopathogen, Erwinia amylovora, causes fire blight, an invasive disease that threatens a wide range of commercial and ornamental Rosaceae host plants. The response elicited by E. amylovora in its host during disease development is similar to the hypersensitive reaction that ty...

Rootstock-regulated gene expression patterns associated with fire blight resistance in apple

USDA-ARS?s Scientific Manuscript database

Background: Desirable apple varieties are clonally propagated by grafting vegetative scions onto rootstocks. Rootstocks influence many phenotypic traits of the scion, including resistance to pathogens such as Erwinia amylovora, which causes fire blight, the most serious bacterial disease of apple....

Disease Alert: Stemphylium Blight

USDA-ARS?s Scientific Manuscript database

Lentil leaves showing symptoms of Stemphylium blight were collected from a lentil field northeast of Garfield (near Idaho border) on July 8, 2013, and incubation of the diseased leaves showed typical spores of the pathogen Stemphylium botryosum or other Stemphylium sp. The field was planted with ‘Mo...

Whole-Genome Sequence of Pseudomonas fluorescens EK007-RG4, a Promising Biocontrol Agent against a Broad Range of Bacteria, Including the Fire Blight Bacterium Erwinia amylovora.

PubMed

Habibi, Roghayeh; Tarighi, Saeed; Behravan, Javad; Taheri, Parissa; Kjøller, Annelise Helene; Brejnrod, Asker; Madsen, Jonas Stenløkke; Sørensen, Søren Johannes

2017-03-30

Here, we report the first draft whole-genome sequence of Pseudomonas fluorescens strain EK007-RG4, which was isolated from the phylloplane of a pear tree. P. fluorescens EK007-RG4 displays strong antagonism against Erwinia amylovora , the causal agent for fire blight disease, in addition to several other pathogenic and non-pathogenic bacteria. Copyright © 2017 Habibi et al.

The fire blight pathogen Erwinia amylovora requires the rpoN gene for pathogenicity in apple.

PubMed

Ramos, Laura S; Lehman, Brian L; Sinn, Judith P; Pfeufer, Emily E; Halbrendt, Noemi O; McNellis, Timothy W

2013-10-01

RpoN is a σ(54) factor regulating essential virulence gene expression in several plant pathogenic bacteria, including Pseudomonas syringae and Pectobacterium carotovorum. In this study, we found that mutation of rpoN in the fire blight pathogen Erwinia amylovora caused a nonpathogenic phenotype. The E. amylovora rpoN Tn5 transposon mutant rpoN1250::Tn5 did not cause fire blight disease symptoms on shoots of mature apple trees. In detached immature apple fruits, the rpoN1250::Tn5 mutant failed to cause fire blight disease symptoms and grew to population levels 12 orders of magnitude lower than the wild-type. In addition, the rpoN1250::Tn5 mutant failed to elicit a hypersensitive response when infiltrated into nonhost tobacco plant leaves, and rpoN1250::Tn5 cells failed to express HrpN protein when grown in hrp (hypersensitive response and pathogenicity)-inducing liquid medium. A plasmid-borne copy of the wild-type rpoN gene complemented all the rpoN1250::Tn5 mutant phenotypes tested. The rpoN1250::Tn5 mutant was prototrophic on minimal solid and liquid media, indicating that the rpoN1250::Tn5 nonpathogenic phenotype was not caused by a defect in basic metabolism or growth. This study provides clear genetic evidence that rpoN is an essential virulence gene of E. amylovora, suggesting that rpoN has the same function in E. amylovora as in P. syringae and Pe. carotovorum. 2013 BSPP and JOHN WILEY & SONS LTD

Erwinia amylovora pyrC mutant causes fire blight despite pyrimidine auxotrophy.

PubMed

Ramos, L S; Sinn, J P; Lehman, B L; Pfeufer, E E; Peter, K A; McNellis, T W

2015-06-01

Erwinia amylovora bacteria cause fire blight disease, which affects apple and pear production worldwide. The Erw. amylovora pyrC gene encodes a predicted dihydroorotase enzyme involved in pyrimidine biosynthesis. Here, we discovered that the Erw. amylovora pyrC244::Tn5 mutant was a uracil auxotroph. Unexpectedly, the Erw. amylovora pyrC244::Tn5 mutant grew as well as the wild-type in detached immature apple and pear fruits. Fire blight symptoms caused by the pyrC244::Tn5 mutant in immature apple and pear fruits were attenuated compared to those caused by the wild-type. The pyrC244::Tn5 mutant also caused severe fire blight symptoms in apple tree shoots. A plasmid-borne copy of the wild-type pyrC gene restored prototrophy and symptom induction in apple and pear fruit to the pyrC244::Tn5 mutant. These results suggest that Erw. amylovora can obtain sufficient pyrimidine from the host to support bacterial growth and fire blight disease development, although de novo pyrimidine synthesis by Erw. amylovora is required for full symptom development in fruits. Significance and impact of the study: This study provides information about the fire blight host-pathogen interaction. Although the Erwinia amylovora pyrC mutant was strictly auxotrophic for pyrimidine, it grew as well as the wild-type in immature pear and apple fruits and caused severe fire blight disease in apple trees. This suggests that Erw. amylovora can obtain sufficient pyrimidines from host tissue to support growth and fire blight disease development. This situation contrasts with findings in some human bacterial pathogens, which require de novo pyrimidine synthesis for growth in host blood, for example. © 2015 The Society for Applied Microbiology.

Novel fusarium head blight pathogens from Nepal and Louisiana revealed by multilocus genealogical concordance

USDA-ARS?s Scientific Manuscript database

This study was conducted to assess evolutionary relationships, species diversity, and trichothecene toxin potential of five Fusarium graminearum complex (FGSC) isolates identified as genetically novel during prior Fusarium head blight (FHB) surveys in Nepal and Louisiana. Results of a multilocus gen...

Priming of Wheat with the Green Leaf Volatile Z-3-Hexenyl Acetate Enhances Defense against Fusarium graminearum But Boosts Deoxynivalenol Production1

PubMed Central

Ameye, Maarten; Audenaert, Kris; De Zutter, Nathalie; Steppe, Kathy; Van Meulebroek, Lieven; Vanhaecke, Lynn; De Vleesschauwer, David; Haesaert, Geert; Smagghe, Guy

2015-01-01

Priming refers to a mechanism whereby plants are sensitized to respond faster and/or more strongly to future pathogen attack. Here, we demonstrate that preexposure to the green leaf volatile Z-3-hexenyl acetate (Z-3-HAC) primed wheat (Triticum aestivum) for enhanced defense against subsequent infection with the hemibiotrophic fungus Fusarium graminearum. Bioassays showed that, after priming with Z-3-HAC, wheat ears accumulated up to 40% fewer necrotic spikelets. Furthermore, leaves of seedlings showed significantly smaller necrotic lesions compared with nonprimed plants, coinciding with strongly reduced fungal growth in planta. Additionally, we found that F. graminearum produced more deoxynivalenol, a mycotoxin, in the primed treatment. Expression analysis of salicylic acid (SA) and jasmonic acid (JA) biosynthesis genes and exogenous methyl salicylate and methyl jasmonate applications showed that plant defense against F. graminearum is sequentially regulated by SA and JA during the early and later stages of infection, respectively. Interestingly, analysis of the effect of Z-3-HAC pretreatment on SA- and JA-responsive gene expression in hormone-treated and pathogen-inoculated seedlings revealed that Z-3-HAC boosts JA-dependent defenses during the necrotrophic infection stage of F. graminearum but suppresses SA-regulated defense during its biotrophic phase. Together, these findings highlight the importance of temporally separated hormone changes in molding plant health and disease and support a scenario whereby the green leaf volatile Z-3-HAC protects wheat against Fusarium head blight by priming for enhanced JA-dependent defenses during the necrotrophic stages of infection. PMID:25713338

Characterization and Comparison of Clavibacter michiganensis subsp. nebraskensis Strains Recovered from Epiphytic and Symptomatic Infections of Maize in Iowa

PubMed Central

Robertson, Alison E.

2015-01-01

Clavibacter michiganensis subsp. nebraskensis (Cmn), the causal organism of Goss’s wilt and leaf blight of maize, can be detected in the phyllosphere of its host prior to disease development. We compared the morphology and pathogenicity of 37 putative isolates of Cmn recovered from asymptomatic and symptomatic maize leaves. Thirty-three of the isolates produced mucoid orange colonies, irrespective of the source of isolation and all but four of these isolates were pathogenic on maize. The remaining 4 isolates recovered from asymptomatic leaves had large fluidal yellow colonies, and were non-pathogenic on maize. Isolates varied in their aggressiveness on a susceptible hybrid of maize but no significant differences in aggressiveness were detected between epiphytic isolates and those recovered from diseased maize tissues. The genomics of Cmn is poorly understood; therefore as a first step to determining what genes may play a role in virulence, we compared 33 putative virulence gene sequences from 6 pathogenic and a non-pathogenic isolate recovered from the phyllosphere. Sequence polymorphisms were detected in 5 genes, cellulase A, two endoglucanases, xylanase B and a pectate lyase but there was no relationship with pathogenicity. Further research is needed to determine what genes play a role in virulence of Cmn. Our data show however, that the virulence factors in Cmn likely differ from those reported for the closely related subspecies michiganensis and sepedonicus. PMID:26599211

Characterization and Comparison of Clavibacter michiganensis subsp. nebraskensis Strains Recovered from Epiphytic and Symptomatic Infections of Maize in Iowa.

PubMed

Ahmad, Azeem; Mbofung, Gladys Y; Acharya, Jyotsna; Schmidt, Clarice L; Robertson, Alison E

2015-01-01

Clavibacter michiganensis subsp. nebraskensis (Cmn), the causal organism of Goss's wilt and leaf blight of maize, can be detected in the phyllosphere of its host prior to disease development. We compared the morphology and pathogenicity of 37 putative isolates of Cmn recovered from asymptomatic and symptomatic maize leaves. Thirty-three of the isolates produced mucoid orange colonies, irrespective of the source of isolation and all but four of these isolates were pathogenic on maize. The remaining 4 isolates recovered from asymptomatic leaves had large fluidal yellow colonies, and were non-pathogenic on maize. Isolates varied in their aggressiveness on a susceptible hybrid of maize but no significant differences in aggressiveness were detected between epiphytic isolates and those recovered from diseased maize tissues. The genomics of Cmn is poorly understood; therefore as a first step to determining what genes may play a role in virulence, we compared 33 putative virulence gene sequences from 6 pathogenic and a non-pathogenic isolate recovered from the phyllosphere. Sequence polymorphisms were detected in 5 genes, cellulase A, two endoglucanases, xylanase B and a pectate lyase but there was no relationship with pathogenicity. Further research is needed to determine what genes play a role in virulence of Cmn. Our data show however, that the virulence factors in Cmn likely differ from those reported for the closely related subspecies michiganensis and sepedonicus.

Paromomycin Derived from Streptomyces sp. AG-P 1441 Induces Resistance against Two Major Pathogens of Chili Pepper.

PubMed

Balaraju, Kotnala; Kim, Chang-Jin; Park, Dong-Jin; Nam, Ki-Woong; Zhang, Kecheng; Sang, Mee Kyung; Park, Kyungseok

2016-09-28

This is the first report that paromomycin, an antibiotic derived from Streptomyces sp. AG-P 1441 (AG-P 1441), controlled Phytophthora blight and soft rot diseases caused by Phytophthora capsici and Pectobacterium carotovorum, respectively, in chili pepper (Capsicum annum L.). Chili pepper plants treated with paromomycin by foliar spray or soil drenching 7 days prior to inoculation with P. capsici zoospores showed significant (p < 0.05) reduction in disease severity (%) when compared with untreated control plants. The disease severity of Phytophthora blight was recorded as 8% and 50% for foliar spray and soil drench, respectively, at 1.0 ppm of paromomycin, compared with untreated control, where disease severity was 83% and 100% by foliar spray and soil drench, respectively. A greater reduction of soft rot lesion areas per leaf disk was observed in treated plants using paromomycin (1.0 μg/ml) by infiltration or soil drench in comparison with untreated control plants. Paromomycin treatment did not negatively affect the growth of chili pepper. Furthermore, the treatment slightly promoted growth; this growth was supported by increased chlorophyll content in paromomycin-treated chili pepper plants. Additionally, paromomycin likely induced resistance as confirmed by the expression of pathogenesis-related (PR) genes: PR-1, β-1,3-glucanase, chitinase, PR-4, peroxidase, and PR-10, which enhanced plant defense against P. capsici in chili pepper. This finding indicates that AG-P 1441 plays a role in pathogen resistance upon the activation of defense genes, by secretion of the plant resistance elicitor, paromomycin.

A barley UDP-glucosyltransferase inactivates nivalenol and provides Fusarium head blight resistance in transgenic wheat

USDA-ARS?s Scientific Manuscript database

Fusarium Head Blight is a disease of cereal crops that causes severe yield losses and mycotoxin contamination of grain. The main causal pathogen, Fusarium graminearum, produces the trichothecene toxins deoxynivalenol or nivalenol as virulence factors. Nivalenol-producing isolates are most prevalent ...

Controlled release of Pantoea agglomerans E325 for biocontrol of fire blight

USDA-ARS?s Scientific Manuscript database

Microencapsulation and controlled release of Pantoea agglomerans strain E325 (E325), which is an antagonist to bacterial pathogen (Erwinia amylovora) of fire blight, a devastating disease of apple and pear, have been investigated. Uniform core-shell alginate microcapsules (AMCs), 60-300 µm in diamet...

Systematics, Phylogeny and Trichothecene Mycotoxin Potential of Fusarium Head Blight Cereal Pathogens

USDA-ARS?s Scientific Manuscript database

Economically devastating outbreaks and epidemics of Fusarium head blight (FHB) or scab of wheat and barley have occurred worldwide over the past two decades. Although the primary etiological agent of FHB was thought to comprise a single panmictic species, Fusarium graminearum, a series of studies we...

Does infection by southern root-knot nematode influence development of Phytophthora blight in pepper?

USDA-ARS?s Scientific Manuscript database

The southern root-knot nematode, Meloidogyne incognita, and Phytophthora capsici, the causal agent of Phytophthora blight, are both important pathogens of pepper (Capsicum annuum L.) in the U.S. and worldwide. Although there is significant information in the literature about the responses of pepper...

Induction of antimicrobial 3-deoxyflavonoids in pome fruit trees controls fire blight.

PubMed

Halbwirth, Heidrun; Fischer, Thilo C; Roemmelt, Susanne; Spinelli, Francesco; Schlangen, Karin; Peterek, Silke; Sabatini, Emidio; Messina, Christian; Speakman, John-Bryan; Andreotti, Carlo; Rademacher, Wilhelm; Bazzi, Carlo; Costa, Guglielmo; Treutter, Dieter; Forkmann, Gert; Stich, Karl

2003-01-01

Fire blight, a devastating bacterial disease in pome fruits, causes severe economic losses worldwide. Hitherto, an effective control could only be achieved by using antibiotics, but this implies potential risks for human health, livestock and environment. A new approach allows transient inhibition of a step in the flavonoid pathway, thereby inducing the formation of a novel antimicrobial 3-deoxyflavonoid controlling fire blight in apple and pear leaves. This compound is closely related to natural phytoalexins in sorghum. The approach does not only provide a safe method to control fire blight: Resistance against different pathogens is also induced in other crop plants.

Diversity and potential impact of Calonectria species in Eucalyptus plantations in Brazil

PubMed Central

Alfenas, R.F.; Lombard, L.; Pereira, O.L.; Alfenas, A.C.; Crous, P.W.

2015-01-01

Species in the genus Calonectria (Hypocreales) represent an important group of plant pathogenic fungi that cause serious losses to plant crops in tropical and subtropical climates. Calonectria leaf blight is currently one of the main impediments to Eucalyptus cultivation in Brazil, and various species of Calonectria have been associated with this disease. Since most previous identifications were solely based on morphological characters, much of the published literature needs to be re-evaluated. The aim of this study was thus to identify and determine the phylogenetic relationships among species that occur in the Eucalyptus growing regions of Brazil by using partial sequences of the β-tubulin, calmodulin, translation elongation factor 1-α and histone H3 gene regions. Based on extensive collections from soil and infected eucalypt leaf samples from plantations, phylogenetic inference revealed the Ca. pteridis complex to be the most common species complex present in Eucalyptus plantations in Brazil. By elucidating taxa in the Ca. pteridis, Ca. cylindrospora and Ca. candelabra species complexes, 20 novel Calonectria species were identified, and a new name in Calonectria provided for Cylindrocladium macrosporum as Ca. pseudopteridis. PMID:26955192

Diversity and potential impact of Calonectria species in Eucalyptus plantations in Brazil.

PubMed

Alfenas, R F; Lombard, L; Pereira, O L; Alfenas, A C; Crous, P W

2015-03-01

Species in the genus Calonectria (Hypocreales) represent an important group of plant pathogenic fungi that cause serious losses to plant crops in tropical and subtropical climates. Calonectria leaf blight is currently one of the main impediments to Eucalyptus cultivation in Brazil, and various species of Calonectria have been associated with this disease. Since most previous identifications were solely based on morphological characters, much of the published literature needs to be re-evaluated. The aim of this study was thus to identify and determine the phylogenetic relationships among species that occur in the Eucalyptus growing regions of Brazil by using partial sequences of the β-tubulin, calmodulin, translation elongation factor 1-α and histone H3 gene regions. Based on extensive collections from soil and infected eucalypt leaf samples from plantations, phylogenetic inference revealed the Ca. pteridis complex to be the most common species complex present in Eucalyptus plantations in Brazil. By elucidating taxa in the Ca. pteridis, Ca. cylindrospora and Ca. candelabra species complexes, 20 novel Calonectria species were identified, and a new name in Calonectria provided for Cylindrocladium macrosporum as Ca. pseudopteridis.

Exploration of Using Antisense Peptide Nucleic Acid (PNA)-cell Penetrating Peptide (CPP) as a Novel Bactericide against Fire Blight Pathogen Erwinia amylovora.

PubMed

Patel, Ravi R; Sundin, George W; Yang, Ching-Hong; Wang, Jie; Huntley, Regan B; Yuan, Xiaochen; Zeng, Quan

2017-01-01

Erwinia amylovora is a Gram-negative bacterial plant pathogen in the family Enterobacteriaceae and is the causal agent of fire blight, a devastating disease of apple and pear. Fire blight is traditionally managed by the application of the antibiotic streptomycin during bloom, but this strategy has been challenged by the development and spread of streptomycin resistance. Thus, there is an urgent need for effective, specific, and sustainable control alternatives for fire blight. Antisense antimicrobials are oligomers of nucleic acid homologs with antisense sequence of essential genes in bacteria. The binding of these molecules to the mRNA of essential genes can result in translational repression and antimicrobial effect. Here, we explored the possibility of developing antisense antimicrobials against E. amylovora and using these compounds in fire blight control. We determined that a 10-nucleotide oligomer of peptide nucleic acid (PNA) targeting the start codon region of an essential gene acpP is able to cause complete growth inhibition of E. amylovora . We found that conjugation of cell penetrating peptide (CPP) to PNA is essential for the antimicrobial effect, with CPP1 [(KFF)3K] being the most effective against E. amylovora . The minimal inhibitory concentration (MIC) of anti- acpP -CPP1 (2.5 μM) is comparable to the MIC of streptomycin (2 μM). Examination of the antimicrobial mechanisms demonstrated that anti- acpP -CPP1 caused dose-dependent reduction of acpP mRNA in E. amylovora upon treatment and resulted in cell death (bactericidal effect). Anti- acpP -CPP1 (100 μM) is able to effectively limit the pathogen growth on stigmas of apple flowers, although less effective than streptomycin. Finally, unlike streptomycin that does not display any specificity in inhibiting pathogen growth, anti- acpP -CPP1 has more specific antimicrobial effect against E. amylovora . In summary, we demonstrated that PNA-CPP can cause an effective, specific antimicrobial effect against E. amylovora and may provide the basis for a novel approach for fire blight control.

Exploration of Using Antisense Peptide Nucleic Acid (PNA)-cell Penetrating Peptide (CPP) as a Novel Bactericide against Fire Blight Pathogen Erwinia amylovora

PubMed Central

Patel, Ravi R.; Sundin, George W.; Yang, Ching-Hong; Wang, Jie; Huntley, Regan B.; Yuan, Xiaochen; Zeng, Quan

2017-01-01

Erwinia amylovora is a Gram-negative bacterial plant pathogen in the family Enterobacteriaceae and is the causal agent of fire blight, a devastating disease of apple and pear. Fire blight is traditionally managed by the application of the antibiotic streptomycin during bloom, but this strategy has been challenged by the development and spread of streptomycin resistance. Thus, there is an urgent need for effective, specific, and sustainable control alternatives for fire blight. Antisense antimicrobials are oligomers of nucleic acid homologs with antisense sequence of essential genes in bacteria. The binding of these molecules to the mRNA of essential genes can result in translational repression and antimicrobial effect. Here, we explored the possibility of developing antisense antimicrobials against E. amylovora and using these compounds in fire blight control. We determined that a 10-nucleotide oligomer of peptide nucleic acid (PNA) targeting the start codon region of an essential gene acpP is able to cause complete growth inhibition of E. amylovora. We found that conjugation of cell penetrating peptide (CPP) to PNA is essential for the antimicrobial effect, with CPP1 [(KFF)3K] being the most effective against E. amylovora. The minimal inhibitory concentration (MIC) of anti-acpP-CPP1 (2.5 μM) is comparable to the MIC of streptomycin (2 μM). Examination of the antimicrobial mechanisms demonstrated that anti-acpP-CPP1 caused dose-dependent reduction of acpP mRNA in E. amylovora upon treatment and resulted in cell death (bactericidal effect). Anti-acpP-CPP1 (100 μM) is able to effectively limit the pathogen growth on stigmas of apple flowers, although less effective than streptomycin. Finally, unlike streptomycin that does not display any specificity in inhibiting pathogen growth, anti-acpP-CPP1 has more specific antimicrobial effect against E. amylovora. In summary, we demonstrated that PNA–CPP can cause an effective, specific antimicrobial effect against E. amylovora and may provide the basis for a novel approach for fire blight control. PMID:28469617

Antimicrobial activity of pyrrocidines from Acremonium zeae against endophytes and pathogens of maize.

PubMed

Wicklow, Donald T; Poling, Stephen M

2009-01-01

Acremonium zeae produces pyrrocidines A and B, which are polyketide-amino acid-derived antibiotics, and is recognized as a seedborne protective endophyte of maize which augments host defenses against microbial pathogens causing seedling blights and stalk rots. Pyrrocidine A displayed significant in vitro activity against Aspergillus flavus and Fusarium verticillioides in assays performed using conidia as inoculum, with pyrrocidine A being more active than B. In equivalent assays performed with conidia or hyphal cells as inoculum, pyrrocidine A revealed potent activity against major stalk and ear rot pathogens of maize, including F. graminearum, Nigrospora oryzae, Stenocarpella (Diplodia) maydis, and Rhizoctonia zeae. Pyrrocidine A displayed significant activity against seed-rotting saprophytes A. flavus and Eupenicillium ochrosalmoneum, as well as seed-infecting colonists of the phylloplane Alternaria alternata, Cladosporium cladosporioides, and Curvularia lunata, which produces a damaging leaf spot disease. Protective endophytes, including mycoparasites which grow asymptomatically within healthy maize tissues, show little sensitivity to pyrrocidines. Pyrrocidine A also exhibited potent activity against Clavibacter michiganense subsp. nebraskense, causal agent of Goss's bacterial wilt of maize, and Bacillus mojaviense and Pseudomonas fluorescens, maize endophytes applied as biocontrol agents, but were ineffective against the wilt-producing bacterium Pantoea stewartii.

Utilizing Bacillus to inhibit the growth and infection by sheath blight pathogen, Rhizoctoniasolani in rice

NASA Astrophysics Data System (ADS)

Margani, R.; Hadiwiyono; Widadi, S.

2018-03-01

Rhizoctonia solani Kuhn is a common pathogen of rice. The pathogen causes sheath blight of rice. The pathogen can cause loss in the production of rice up to 45%. So far, the disease however is still poorly taken care of by the farmers and researchers, so the control measures is nearly never practiced by the farmers in the fields. It due to the unavailability of effective control method of the disease. Therefore, development to control the disease is important. Bacillus is one of popular bacteria which is effective as biological control agent of a lot of pathogens in plants, but it has not been used for control sheath blight in rice yet. The current researches were aimed to study the potential of Bacillus collected from healthy rice as candidates of biological control agent of the disease. The results showed that some isolates showed indications to inhibit significantly the growth and infection of the pathogen. We obtained at least five isolates of Bacillus collected from leaves, sheath, and stem of healthy rice fields. All of the isolates could effectively inhibit the growth of R. solani in vitro on potato dextrose medium at range 30.33-58.00%, whereas in vivo B05 isolate was the most effective in inhibiting the infection of pathogen at 30.43%. It was not significantly different (P≥0.05) to application of hexaconazol with dosage of 2 ml L-1.

Multilocus Genotyping and Molecular Phylogenetics Resolve a Novel Head Blight Pathogen within the Fusarium graminearum Species Complex from Ethiopia

USDA-ARS?s Scientific Manuscript database

A survey of Fusarium head blight (FHB)-contaminated wheat in Ethiopia recovered 31 isolates resembling members of the Fusarium graminearum species complex. Results of a multilocus genotyping (MLGT) assay for FHB species and trichothecene chemotype determination suggested that 22 of these isolates m...

Germplasm Evaluation for Resistance and Monitoring Bacterial Panicle Blight Disease of Rice in Arkansas, 2016

USDA-ARS?s Scientific Manuscript database

Bacterial panicle blight (BPB), caused by a bacterial pathogen, mainly Burkholderia glumae, has posed a higher level of threat to rice production worldwide in recent years. Here we report the response of over 300 entries evaluated by artificially inoculating with a bacterial suspension under field c...

Nut cold hardiness as a factor influencing the restoration of American chestnut in northern latitudes and high elevations

Treesearch

Thomas M. Saielli; Paul G. Schaberg; Gary J. Hawley; Joshua M. Halman; Kendra M. Gurney

2012-01-01

American chestnut (Castanea dentata (Marsh.) Borkh.) was functionally removed as a forest tree by chestnut blight (caused by the fungal pathogen Cryphonectria parasitica (Murr.) Barr). Hybrid-backcross breeding between blight-resistant Chinese chestnut (Castanea mollissima Blume) and American chestnut is used to...

Regional differences in the composition of Fusarium head blight pathogens and mycotoxins associated with wheat in Mexico

USDA-ARS?s Scientific Manuscript database

Fusarium Head Blight (FHB) is a destructive disease of small grain cereals and a major food safety concern. Epidemics result in substantial yield losses, reduction in crop quality, and contamination of grains with trichothecenes and other mycotoxins. A number of different fusaria can cause FHB, and ...

Role of temperature and free moisture in onion flower blight. [Botrytis squamosa; Botrytis cinerea; and Botrytis allii

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ramsey, G.R.; Lorbeer, J.W.

1986-06-01

The cardinal temperatures at which onion umbels were blighted (after inoculation when two-thirds of the florets were open) with Botrytis squamosa, B. cinerea, and B. allii (isolated from blighted onion florets) were near 9, 21, and 27 C for B. squamosa, near 12, 21, and 30 C for B. cinerea, and near 9, 24, and 30 C for B. allii. The cardinal temperatures for mycelial growth (potato-dextrose agar) of B. squamosa, B. cinerea, and B. allii were near 5, 22, and 30 C for each fungus. The cardinal temperatures for conidial germination (on purified water agar) were near 6, 15,more » and 30 C for B. squamosa; 3, 18, and 33 C for B. cinerea; and 6, 24, and 33 C for B. allii. When the duration of free moisture on umbels after inoculation with the three pathogens was increased from 0 to 96 hr. the percentages of unopened florets, open florets, and immature seed capsules blighted at 21 C were increased significantly. Free moisture durations of 12-24, 6-12, and 6-12 hr were necessary for blighting of unopen florets, open florets, and immature seed capsules, respectively, by each pathogen at 21 C. A positive correlation between the amount of July rainfall and the natural incidence of onion flower blight was observed in Orange County, New York, from 1976 to 1981. 10 references, 2 figures, 1 table.« less

Stemphylium Leaf Blight of Garlic (Allium sativum ) in Spain: Taxonomy and In Vitro Fungicide Response

PubMed Central

Gálvez, Laura; Gil-Serna, Jéssica; García, Marta; Iglesias, Concepción; Palmero, Daniel

2016-01-01

The most serious aerial disease of garlic is leaf blight caused by Stemphylium spp. Geographical variation in the causal agent of this disease is indicated. Stemphylium vesicarium has been reported in Spain, whereas S. solani is the most prevalent species recorded in China. In this study, Stemphylium isolates were obtained from symptomatic garlic plants sampled from the main Spanish production areas. Sequence data for the ITS1–5.8S–ITS2 region enabled assignation of the isolates to the Pleospora herbarum complex and clearly distinguished the isolates from S. solani. Conidial morphology of the isolates corresponded to that of S. vesicarium and clearly discriminated them from S. alfalfae and S. herbarum on the basis of the size and septation pattern of mature conidia. Conidial morphology as well as conidial length, width and length:width ratio also allowed the Spanish isolates to be distinguished from S. botryosum and S. herbarum. Control of leaf blight of garlic is not well established. Few studies are available regarding the effectiveness of chemical treatments to reduce Stemphylium spp. incidence on garlic. The effectiveness of nine fungicides of different chemical groups to reduce Stemphylium mycelial growth in vitro was tested. Boscalid + pyraclostrobin (group name, succinate dehydrogenase inhibitors + quinone outside inhibitors), iprodione (dicar-boximide), and prochloraz (demethylation inhibitors) were highly effective at reducing mycelial growth in S. vesicarium with EC50 values less than 5 ppm. In general, the effectiveness of the fungicide was enhanced with increasing dosage. PMID:27721688

Inhibition of OsSWEET11 function in mesophyll cells improves resistance of rice to sheath blight disease.

PubMed

Gao, Yue; Zhang, Chong; Han, Xiao; Wang, Zi Yuan; Ma, Lai; Yuan, De Peng; Wu, Jing Ni; Zhu, Xiao Feng; Liu, Jing Miao; Li, Dao Pin; Hu, Yi Bing; Xuan, Yuan Hu

2018-04-16

Pathogen-host interaction is a complicated process; pathogens mainly infect host plants to acquire nutrients, especially sugars. Rhizoctonia solani, the causative agent of sheath blight disease, is a major pathogen of rice. However, it is not known, as to how this pathogen obtains sugar from rice plants. In this study, we found that the rice sugar transporter, OsSWEET11 is involved in the pathogenesis of sheath blight disease. qRT-PCR and β-d-glucuronidase expression analyses showed that R. solani infection significantly enhanced OsSWEET11 expression in leaves among the clade III SWEET members. The analyses of transgenic plants revealed that Ossweet11 mutants were less susceptible, whereas plants overexpressing OsSWEET11 were more susceptible to sheath blight compared to wild-type controls, but the yield of OsSWEET11 mutants and overexpressors was reduced. SWEETs become active upon oligomerization. Split-ubiquitin yeast two-hybrid, bimolecular fluorescence complementation, and coimmunoprecipitation assays showed that mutated-OsSWEET11 interacted with normal OsSWEET11. In addition, expressing conserved residue mutated-AtSWEET1 inhibits normal AtSWEET1 activity. To analyze whether inhibition of OsSWEET11 function in mesophyll cells is related to defense against this disease, mutated- OsSWEET11 was expressed under the control of Rubisco promoter, which is specific for green tissues. The resistance of transgenic plants to sheath blight disease, but not other disease was improved, while yield production was not evidently affected. Overall, these results suggest that R. solani might acquire sugar from rice leaves by activating OsSWEET11 expression. The plants can be protected from infection by manipulating the expression of OsSWEET11 without affecting the crop yield. This article is protected by copyright. All rights reserved. © 2018 BSPP and John Wiley & Sons Ltd.

The sentinel tree nursery as an early warning system for pathway risk assessment: Fungal pathogens associated with Chinese woody plants commonly shipped to Europe

PubMed Central

Vettraino, Anna Maria; Li, Hong-Mei; Eschen, Rene; Morales-Rodriguez, Carmen

2017-01-01

Introduction of and invasion by alien plant pathogens represents the main cause of emerging infectious diseases affecting domesticated and wild plant species worldwide. The trade in living plants is the most common pathway of introduction. Many of the alien tree pathogens recently introduced into Europe were not previously included on any quarantine lists. To help determine the potential risk of pest introduction through trading of ornamental plants, a sentinel nursery was established in Beijing, China in 2008. The sentinel nursery planting included four of the most common ornamental woody species shipped to Europe including Ilex cornuta var. fortunae, Zelkova schneideriana, Fraxinus chinensis and Buxus microphylla. Symptoms developing on these species within the sentinel nursery were detected in 2013 and consisted of necrotic spots on leaves, canker and stem necrosis, shoot blight and shoot necrosis. Fungi associated with the trees and their symptoms included Alternaria alternata detected from all hosts; Diaporthe liquidambaris and Diaporthe capsici from bark and leaf necrosis of Zelkova schneideriana; Botryosphaeria dothidea and Nothophoma quercina from stem cankers on Fraxinus chinensis and leaf necrosis on Ilex cornuta; and Pseudonectria foliicola from leaf necrosis on Buxus microphylla. Next generation sequencing analysis from asymptomatic tissues detected eighteen OTU’s at species level among which some taxa had not been previously recorded in Europe. These results clearly demonstrate that looking at trees of internationally traded species in the region of origin can reveal the presence of potentially harmful organisms of major forestry, landscape or crop trees. Results of this study also provide an indication as to how some disease agents can be introduced using pathways other than the co-generic hosts. Hence, sentinel nurseries represent one potential mechanism to address the current lack of knowledge about pests in the countries from where live plants are shipped and the threats they represent to native flora and crops in importing countries. PMID:29186190

The sentinel tree nursery as an early warning system for pathway risk assessment: Fungal pathogens associated with Chinese woody plants commonly shipped to Europe.

PubMed

Vettraino, Anna Maria; Li, Hong-Mei; Eschen, Rene; Morales-Rodriguez, Carmen; Vannini, Andrea

2017-01-01

Introduction of and invasion by alien plant pathogens represents the main cause of emerging infectious diseases affecting domesticated and wild plant species worldwide. The trade in living plants is the most common pathway of introduction. Many of the alien tree pathogens recently introduced into Europe were not previously included on any quarantine lists. To help determine the potential risk of pest introduction through trading of ornamental plants, a sentinel nursery was established in Beijing, China in 2008. The sentinel nursery planting included four of the most common ornamental woody species shipped to Europe including Ilex cornuta var. fortunae, Zelkova schneideriana, Fraxinus chinensis and Buxus microphylla. Symptoms developing on these species within the sentinel nursery were detected in 2013 and consisted of necrotic spots on leaves, canker and stem necrosis, shoot blight and shoot necrosis. Fungi associated with the trees and their symptoms included Alternaria alternata detected from all hosts; Diaporthe liquidambaris and Diaporthe capsici from bark and leaf necrosis of Zelkova schneideriana; Botryosphaeria dothidea and Nothophoma quercina from stem cankers on Fraxinus chinensis and leaf necrosis on Ilex cornuta; and Pseudonectria foliicola from leaf necrosis on Buxus microphylla. Next generation sequencing analysis from asymptomatic tissues detected eighteen OTU's at species level among which some taxa had not been previously recorded in Europe. These results clearly demonstrate that looking at trees of internationally traded species in the region of origin can reveal the presence of potentially harmful organisms of major forestry, landscape or crop trees. Results of this study also provide an indication as to how some disease agents can be introduced using pathways other than the co-generic hosts. Hence, sentinel nurseries represent one potential mechanism to address the current lack of knowledge about pests in the countries from where live plants are shipped and the threats they represent to native flora and crops in importing countries.

Genetic of virulence in Ascochyta rabiei

USDA-ARS?s Scientific Manuscript database

Many attempts have been made to classify variation in virulence of the chickpea Ascochyta blight pathogen, Ascochyta rabiei, into discrete categories referred to as “pathogenic groups”, “races” or “pathotypes”. Results have been inconsistent and conflicting due to differences in host and pathogen...

The rise and fall of the Phytophthora infestans lineage that triggered the Irish potato famine

USDA-ARS?s Scientific Manuscript database

Potato late blight, caused by the oomycete Phytophthora infestans, is a plant pathogen of historical dimension that remains one of the world’s most destructive crop diseases. Ever since its first global outbreak of the 1840s that culminated in the Great Famine in Ireland, late blight has been a majo...

Thymol-based sub-micron emulsions exhibit antifungal activity against Fusarium graminearum and inhibit Fusarium head blight (FHB) in wheat

USDA-ARS?s Scientific Manuscript database

Fusarium graminearum is a very destructive fungal pathogen that leads to Fusarium head blight (FHB) in wheat, a disease that costs growers millions of dollars annually both in crop losses and control measures. Current countermeasures include the deployment of wheat varieties with some resistance to ...

Population genetic structure and mycotoxin potential of the wheat crown rot and head blight pathogen Fusarium culmorum in Algeria

USDA-ARS?s Scientific Manuscript database

Surveys for crown rot (FCR) and head blight (FHB) of Algerian wheat conducted during 2014 and 2015 revealed that Fusarium culmorum strains producing 3-acetyl-deoxynivalenol (3ADON) or nivalenol (NIV) were the primary causal agents of these important diseases. Morphological identification of the isol...

First report of Fusarium graminearum, F. asiaticum and F. cortaderiae as head blight pathogens of annual ryegrass in Brazil

USDA-ARS?s Scientific Manuscript database

Members of the Fusarium graminearum species complex (FGSC) cause Fusarium head blight (FHB) of small grains and several grasses, including annual ryegrass (Lolium multiflorum Lam.), an important forage crop, but also a common weed in wheat, rice and maize agroecosystem in southern Brazil. Although i...

Genomic analysis of Bacillus subtilis OH 131.1 and coculturing with Cryptococcus flavescens for control of fusarium head blight

USDA-ARS?s Scientific Manuscript database

Bacillus subtilis OH131.1 is a bacterial antagonist of Fusarium graminearum, a plant pathogen which causes Fusarium head blight in wheat. The genome of B. subtilis OH131.1 was sequenced, annotated and analyzed to understand its potential to produce bioactive metabolites. The analysis identified 6 sy...

AraC/XylS family stress response regulators Rob, SoxS, PliA, and OpiA in the fire blight pathogen Erwinia amylovora.

PubMed

Pletzer, Daniel; Schweizer, Gabriel; Weingart, Helge

2014-09-01

Transcriptional regulators of the AraC/XylS family have been associated with multidrug resistance, organic solvent tolerance, oxidative stress, and virulence in clinically relevant enterobacteria. In the present study, we identified four homologous AraC/XylS regulators, Rob, SoxS, PliA, and OpiA, from the fire blight pathogen Erwinia amylovora Ea1189. Previous studies have shown that the regulators MarA, Rob, and SoxS from Escherichia coli mediate multiple-antibiotic resistance, primarily by upregulating the AcrAB-TolC efflux system. However, none of the four AraC/XylS regulators from E. amylovora was able to induce a multidrug resistance phenotype in the plant pathogen. Overexpression of rob led to a 2-fold increased expression of the acrA gene. However, the rob-overexpressing strain showed increased resistance to only a limited number of antibiotics. Furthermore, Rob was able to induce tolerance to organic solvents in E. amylovora by mechanisms other than efflux. We demonstrated that SoxS from E. amylovora is involved in superoxide resistance. A soxS-deficient mutant of Ea1189 was not able to grow on agar plates supplemented with the superoxide-generating agent paraquat. Furthermore, expression of soxS was induced by redox cycling agents. We identified two novel members of the AraC/XylS family in E. amylovora. PliA was highly upregulated during the early infection phase in apple rootstock and immature pear fruits. Multiple compounds were able to induce the expression of pliA, including apple leaf extracts, phenolic compounds, redox cycling agents, heavy metals, and decanoate. OpiA was shown to play a role in the regulation of osmotic and alkaline pH stress responses. Copyright © 2014, American Society for Microbiology. All Rights Reserved.

Harpin Hpa1 Interacts with Aquaporin PIP1;4 to Promote the Substrate Transport and Photosynthesis in Arabidopsis.

PubMed

Li, Liang; Wang, Hao; Gago, Jorge; Cui, Haiying; Qian, Zhengjiang; Kodama, Naomi; Ji, Hongtao; Tian, Shan; Shen, Dan; Chen, Yanjuan; Sun, Fengli; Xia, Zhonglan; Ye, Qing; Sun, Wei; Flexas, Jaume; Dong, Hansong

2015-11-26

Harpin proteins produced by plant-pathogenic Gram-negative bacteria are the venerable player in regulating bacterial virulence and inducing plant growth and defenses. A major gap in these effects is plant sensing linked to cellular responses, and plant sensor for harpin Hpa1 from rice bacterial blight pathogen points to plasma membrane intrinsic protein (PIP). Here we show that Arabidopsis AtPIP1;4 is a plasma membrane sensor of Hpa1 and plays a dual role in plasma membrane permeability of CO2 and H2O. In particular, AtPIP1;4 mediates CO2 transport with a substantial contribute to photosynthesis and further increases this function upon interacting with Hpa1 at the plasma membrane. As a result, leaf photosynthesis rates are increased and the plant growth is enhanced in contrast to the normal process without Hpa1-AtPIP1;4 interaction. Our findings demonstrate the first case that plant sensing of a bacterial harpin protein is connected with photosynthetic physiology to regulate plant growth.

Harpin Hpa1 Interacts with Aquaporin PIP1;4 to Promote the Substrate Transport and Photosynthesis in Arabidopsis

PubMed Central

Li, Liang; Wang, Hao; Gago, Jorge; Cui, Haiying; Qian, Zhengjiang; Kodama, Naomi; Ji, Hongtao; Tian, Shan; Shen, Dan; Chen, Yanjuan; Sun, Fengli; Xia, Zhonglan; Ye, Qing; Sun, Wei; Flexas, Jaume; Dong, Hansong

2015-01-01

Harpin proteins produced by plant-pathogenic Gram-negative bacteria are the venerable player in regulating bacterial virulence and inducing plant growth and defenses. A major gap in these effects is plant sensing linked to cellular responses, and plant sensor for harpin Hpa1 from rice bacterial blight pathogen points to plasma membrane intrinsic protein (PIP). Here we show that Arabidopsis AtPIP1;4 is a plasma membrane sensor of Hpa1 and plays a dual role in plasma membrane permeability of CO2 and H2O. In particular, AtPIP1;4 mediates CO2 transport with a substantial contribute to photosynthesis and further increases this function upon interacting with Hpa1 at the plasma membrane. As a result, leaf photosynthesis rates are increased and the plant growth is enhanced in contrast to the normal process without Hpa1-AtPIP1;4 interaction. Our findings demonstrate the first case that plant sensing of a bacterial harpin protein is connected with photosynthetic physiology to regulate plant growth. PMID:26607179

Biocontrol Efficacy of Formulated Pseudomonas chlororaphis O6 against Plant Diseases and Root-Knot Nematodes

PubMed Central

Nam, Hyo Song; Anderson, Anne J.; Kim, Young Cheol

2018-01-01

Commercial biocontrol of microbial plant diseases and plant pests, such as nematodes, requires field-effective formulations. The isolate Pseudomonas chlororaphis O6 is a Gram-negative bacterium that controls microbial plant pathogens both directly and indirectly. This bacterium also has nematocidal activity. In this study, we report on the efficacy of a wettable powder-type formulation of P. chlororaphis O6. Culturable bacteria in the formulated product were retained at above 1 × 108 colony forming units/g after storage of the powder at 25 °C for six months. Foliar application of the diluted formulated product controlled leaf blight and gray mold in tomato. The product also displayed preventative and curative controls for root-knot nematode (Meloidogyne spp.) in tomato. Under laboratory conditions and for commercially grown melon, the control was at levels comparable to that of a standard commercial chemical nematicide. The results indicated that the wettable powder formulation product of P. chlororaphis O6 can be used for control of plant microbial pathogens and root-knot nematodes. PMID:29887780

LAMP detection assays for boxwood blight pathogens: a comparative genomics approach

USDA-ARS?s Scientific Manuscript database

Rapid and accurate molecular diagnostic tools are critical to efforts to minimize the impact and spread of emergent pathogens. The identification of diagnostic markers for novel pathogens presents several challenges, especially in the absence of information about population diversity, and where gen...

A Single, Plastic Population of Mycosphaerella pinodes Causes Ascochyta Blight on Winter and Spring Peas (Pisum sativum) in France

PubMed Central

Guibert, Michèle; Leclerc, Aurélie; Andrivon, Didier; Tivoli, Bernard

2012-01-01

Plant diseases are caused by pathogen populations continuously subjected to evolutionary forces (genetic flow, selection, and recombination). Ascochyta blight, caused by Mycosphaerella pinodes, is one of the most damaging necrotrophic pathogens of field peas worldwide. In France, both winter and spring peas are cultivated. Although these crops overlap by about 4 months (March to June), primary Ascochyta blight infections are not synchronous on the two crops. This suggests that the disease could be due to two different M. pinodes populations, specialized on either winter or spring pea. To test this hypothesis, 144 pathogen isolates were collected in the field during the winter and spring growing seasons in Rennes (western France), and all the isolates were genotyped using amplified fragment length polymorphism (AFLP) markers. Furthermore, the pathogenicities of 33 isolates randomly chosen within the collection were tested on four pea genotypes (2 winter and 2 spring types) grown under three climatic regimes, simulating winter, late winter, and spring conditions. M. pinodes isolates from winter and spring peas were genetically polymorphic but not differentiated according to the type of cultivars. Isolates from winter pea were more pathogenic than isolates from spring pea on hosts raised under winter conditions, while isolates from spring pea were more pathogenic than those from winter pea on plants raised under spring conditions. These results show that disease developed on winter and spring peas was initiated by a single population of M. pinodes whose pathogenicity is a plastic trait modulated by the physiological status of the host plant. PMID:23023742

Antifungal metabolites (monorden, monocillins I, II, III) from Colletotrichum graminicola, a systemic vascular pathogen of maize.

PubMed

Wicklow, Donald T; Jordan, Annalisa M; Gloer, James B

2009-12-01

Colletotrichum graminicola is a systemic vascular pathogen that causes anthracnose stalk rot and leaf blight of maize. In the course of an effort to explore the potential presence and roles of C. graminicola metabolites in maize, ethyl acetate extracts of solid substrate fermentations of several C. graminicola isolates from Michigan and Illinois were found to be active against Aspergillus flavus and Fusarium verticillioides, both mycotoxin-producing seed-infecting fungal pathogens. Chemical investigations of the extract of one such isolate (NRRL 47511) led to the isolation of known metabolites monorden (also known as radicicol) and monocillins I-III as major components. Monorden and monocillin I displayed in vitro activity against the stalk- and ear-rot pathogen Stenocarpella maydis while only the most abundant metabolite (monorden) showed activity against foliar pathogens Alternaria alternata, Bipolaris zeicola, and Curvularia lunata. Using LC-HRESITOFMS, monorden was detected in steam-sterilized maize stalks and stalk residues inoculated with C. graminicola but not in the necrotic stalk tissues of wound-inoculated plants grown in an environmental chamber. Monorden and monocillin I can bind and inhibit plant Hsp90, a chaperone of R-proteins. It is hypothesized that monorden and monocillins could support the C. graminicola disease cycle by disrupting maize plant defenses and by excluding other fungi from necrotic tissues and crop residues. This is the first report of natural products from C. graminicola, as well as the production of monorden and monocillins by a pathogen of cereals.

Purification, crystal structure and antimicrobial activity of phenazine-1-carboxamide produced by a growth-promoting biocontrol bacterium, Pseudomonas aeruginosa MML2212.

PubMed

Shanmugaiah, V; Mathivanan, N; Varghese, B

2010-02-01

To purify and characterize an antimicrobial compound produced by a biocontrol bacterium, Pseudomonas aeruginosa MML2212, and evaluate its activity against rice pathogens, Rhizoctonia solani and Xanthomonas oryzae pv. oryzae. Pseudomonas aeruginosa strain MML2212 isolated from the rice rhizosphere with wide-spectrum antimicrobial activity was cultured in Kings'B broth using a fermentor for 36 h. The extracellular metabolites were isolated from the fermented broth using ethyl acetate extraction and purified by two-step silica-gel column chromatography. Three fractions were separated, of which a major compound was obtained in pure state as yellow needles. It was crystallized after dissolving with chloroform followed by slow evaporation. It is odourless with a melting point of 220-222 degrees C. It was soluble in most of the organic solvents and poorly soluble in water. The molecular mass of purified compound was estimated as 223.3 by mass spectral analysis. Further, it was characterized by IR, (1)H and (13)C NMR spectral analyses. The crystal structure of the compound was elucidated for the first time by X-ray diffraction study and deposited in the Cambridge Crystallographic Data Centre (http://www.ccde.com.ac.uk) with the accession no. CCDC 617344. The crystal compound was undoubtedly identified as phenazine-1-carboxamide (PCN) with the empirical formula of C(13)H(9)N(3)O. As this is the first report on the crystal structure of PCN, it provides additional information to the structural chemistry. Furthermore, the present study reports the antimicrobial activity of purified PCN on major rice pathogens, R. solani and X. oryzae pv. oryzae. Therefore, the PCN can be developed as an ideal agrochemical candidate for the control of both sheath blight and bacterial leaf blight diseases of rice.

II. Pathogens

Treesearch

Ned B. Klopfenstein; Brian W. Geils

2011-01-01

Invasive fungal pathogens have caused immeasurably large ecological and economic damage to forests. It is well known that invasive fungal pathogens can cause devastating forest diseases (e.g., white pine blister rust, chestnut blight, Dutch elm disease, dogwood anthracnose, butternut canker, Scleroderris canker of pines, sudden oak death, pine pitch canker) (Maloy 1997...

In vivo assessment of plant extracts for control of plant diseases: A sesquiterpene ketolactone isolated from Curcuma zedoaria suppresses wheat leaf rust.

PubMed

Han, Jae Woo; Shim, Sang Hee; Jang, Kyoung Soo; Choi, Yong Ho; Dang, Quang Le; Kim, Hun; Choi, Gyung Ja

2018-02-01

As an alternative to synthetic pesticides, natural materials such as plant extracts and microbes have been considered to control plant diseases. In this study, methanol extracts of 120 plants were explored for in vivo antifungal activity against Rhizoctonia solani, Botrytis cinerea, Phytophthora infestans, Puccinia triticina, and Blumeria graminis f. sp. hordei. Of the 120 plant extracts, eight plant extracts exhibited a disease control efficacy of more than 90% against at least one of five plant diseases. In particular, a methanol extract of Curcuma zedoaria rhizomes exhibited strong activity against wheat leaf rust caused by P. triticina. When the C. zedoaria methanol extracts were partitioned with various solvents, the layers of n-hexane, methylene chloride, and ethyl acetate showed disease control values of 100, 80, and 43%, respectively, against wheat leaf rust. From the C. zedoaria rhizome extracts, an antifungal substance was isolated and identified as a sesquiterpene ketolactone based on the mass and nuclear magnetic resonance spectral data. The active compound controlled the development of rice sheath blight, wheat leaf rust, and tomato late blight. Considering the in vivo antifungal activities of the sesquiterpene ketolactone and the C. zedoaria extracts, these results suggest that C. zedoaria can be used as a potent fungicide in organic agriculture.

Inheritance of high levels of resistance to common bacterial blight caused by Xanthomonas Axonopodis pv. Phaseoli in common bean (Phaseolus vulgaris L.)

USDA-ARS?s Scientific Manuscript database

Common bacterial blight caused by the pathogen Xanthomonas axonopodis pv. phaseoli (Xap) is an important biotic factor limiting common bean (Phaseolus vulgaris L.) production. A few interspecific bean breeding lines such as VAX 6 exhibit a high level of resistance to a wide range of Xap strains repr...

Developing hazelnuts (Corylus spp.) with durable resistance to eastern filbert blight caused by Anisogramma anomala

Treesearch

Thomas J. Molnar; John Capik; Clayton W. Leadbetter; Ning Zhang; Guohong Cai; Bradley I. Hillman

2012-01-01

Eastern filbert blight (EFB) is a devastating fungal disease of European hazelnut, Corylus avellana L., and is considered to be the primary reason hazelnuts have not been developed as a commercial crop in the eastern United States. The pathogen, Anisogramma anomala, is native to a wide area east of the Rocky Mountains, where it...

Control of plant defense mechanisms and fire blight pathogenesis through the regulation of 6-thioguanine biosynthesis in Erwinia amylovora.

PubMed

Coyne, Sébastien; Litomska, Agnieszka; Chizzali, Cornelia; Khalil, Mohammed N A; Richter, Klaus; Beerhues, Ludger; Hertweck, Christian

2014-02-10

Fire blight is a devastating disease of Rosaceae plants, such as apple and pear trees. It is characterized by necrosis of plant tissue, caused by the phytopathogenic bacterium Erwinia amylovora. The plant pathogen produces the well-known antimetabolite 6-thioguanine (6TG), which plays a key role in fire blight pathogenesis. Here we report that YcfR, a member of the LTTR family, is a major regulator of 6TG biosynthesis in E. amylovora. Inactivation of the regulator gene (ycfR) led to dramatically decreased 6TG production. Infection assays with apple plants (Malus domestica cultivar Holsteiner Cox) and cell cultures of Sorbus aucuparia (mountain ash, rowan) revealed abortive fire blight pathogenesis and reduced plant response (biphenyl and dibenzofuran phytoalexin production). In the presence of the ΔycfR mutant, apple trees were capable of activating the abscission machinery to remove infected tissue. In addition to unveiling the regulation of 6TG biosynthesis in a major plant pathogen, we demonstrate for the first time that this antimetabolite plays a pivotal role in dysregulating the plant response to infection. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Putative resistance gene markers associated with quantitative trait loci for fire blight resistance in Malus ‘Robusta 5’ accessions

PubMed Central

2012-01-01

Background Breeding of fire blight resistant scions and rootstocks is a goal of several international apple breeding programs, as options are limited for management of this destructive disease caused by the bacterial pathogen Erwinia amylovora. A broad, large-effect quantitative trait locus (QTL) for fire blight resistance has been reported on linkage group 3 of Malus ‘Robusta 5’. In this study we identified markers derived from putative fire blight resistance genes associated with the QTL by integrating further genetic mapping studies with bioinformatics analysis of transcript profiling data and genome sequence databases. Results When several defined E.amylovora strains were used to inoculate three progenies from international breeding programs, all with ‘Robusta 5’ as a common parent, two distinct QTLs were detected on linkage group 3, where only one had previously been mapped. In the New Zealand ‘Malling 9’ X ‘Robusta 5’ population inoculated with E. amylovora ICMP11176, the proximal QTL co-located with SNP markers derived from a leucine-rich repeat, receptor-like protein ( MxdRLP1) and a closely linked class 3 peroxidase gene. While the QTL detected in the German ‘Idared’ X ‘Robusta 5’ population inoculated with E. amylovora strains Ea222_JKI or ICMP11176 was approximately 6 cM distal to this, directly below a SNP marker derived from a heat shock 90 family protein gene ( HSP90). In the US ‘Otawa3’ X ‘Robusta5’ population inoculated with E. amylovora strains Ea273 or E2002a, the position of the LOD score peak on linkage group 3 was dependent upon the pathogen strains used for inoculation. One of the five MxdRLP1 alleles identified in fire blight resistant and susceptible cultivars was genetically associated with resistance and used to develop a high resolution melting PCR marker. A resistance QTL detected on linkage group 7 of the US population co-located with another HSP90 gene-family member and a WRKY transcription factor previously associated with fire blight resistance. However, this QTL was not observed in the New Zealand or German populations. Conclusions The results suggest that the upper region of ‘Robusta 5’ linkage group 3 contains multiple genes contributing to fire blight resistance and that their contributions to resistance can vary depending upon pathogen virulence and other factors. Mapping markers derived from putative fire blight resistance genes has proved a useful aid in defining these QTLs and developing markers for marker-assisted breeding of fire blight resistance. PMID:22471693

Perturbation of Maize Phenylpropanoid Metabolism by an AvrE Family Type III Effector from Pantoea stewartii1[OPEN

PubMed Central

Asselin, Jo Ann E.; Lin, Jinshan; Perez-Quintero, Alvaro L.; Gentzel, Irene; Majerczak, Doris; Opiyo, Stephen O.; Zhao, Wanying; Paek, Seung-Mann; Kim, Min Gab; Coplin, David L.; Blakeslee, Joshua J.; Mackey, David

2015-01-01

AvrE family type III effector proteins share the ability to suppress host defenses, induce disease-associated cell death, and promote bacterial growth. However, despite widespread contributions to numerous bacterial diseases in agriculturally important plants, the mode of action of these effectors remains largely unknown. WtsE is an AvrE family member required for the ability of Pantoea stewartii ssp. stewartii (Pnss) to proliferate efficiently and cause wilt and leaf blight symptoms in maize (Zea mays) plants. Notably, when WtsE is delivered by a heterologous system into the leaf cells of susceptible maize seedlings, it alone produces water-soaked disease symptoms reminiscent of those produced by Pnss. Thus, WtsE is a pathogenicity and virulence factor in maize, and an Escherichia coli heterologous delivery system can be used to study the activity of WtsE in isolation from other factors produced by Pnss. Transcriptional profiling of maize revealed the effects of WtsE, including induction of genes involved in secondary metabolism and suppression of genes involved in photosynthesis. Targeted metabolite quantification revealed that WtsE perturbs maize metabolism, including the induction of coumaroyl tyramine. The ability of mutant WtsE derivatives to elicit transcriptional and metabolic changes in susceptible maize seedlings correlated with their ability to promote disease. Furthermore, chemical inhibitors that block metabolic flux into the phenylpropanoid pathways targeted by WtsE also disrupted the pathogenicity and virulence activity of WtsE. While numerous metabolites produced downstream of the shikimate pathway are known to promote plant defense, our results indicate that misregulated induction of phenylpropanoid metabolism also can be used to promote pathogen virulence. PMID:25635112

Cryphonectria parasitica, the causal agent of chestnut blight: invasion history, population biology and disease control.

PubMed

Rigling, Daniel; Prospero, Simone

2018-01-01

Chestnut blight, caused by Cryphonectria parasitica, is a devastating disease infecting American and European chestnut trees. The pathogen is native to East Asia and was spread to other continents via infected chestnut plants. This review summarizes the current state of research on this pathogen with a special emphasis on its interaction with a hyperparasitic mycovirus that acts as a biological control agent of chestnut blight. Cryphonectria parasitica (Murr.) Barr. is a Sordariomycete (ascomycete) fungus in the family Cryphonectriaceae (Order Diaporthales). Closely related species that can also be found on chestnut include Cryphonectria radicalis, Cryphonectria naterciae and Cryphonectria japonica. Major hosts are species in the genus Castanea (Family Fagaceae), particularly the American chestnut (C. dentata), the European chestnut (C. sativa), the Chinese chestnut (C. mollissima) and the Japanese chestnut (C. crenata). Minor incidental hosts include oaks (Quercus spp.), maples (Acer spp.), European hornbeam (Carpinus betulus) and American chinkapin (Castanea pumila). Cryphonectria parasitica causes perennial necrotic lesions (so-called cankers) on the bark of stems and branches of susceptible host trees, eventually leading to wilting of the plant part distal to the infection. Chestnut blight cankers are characterized by the presence of mycelial fans and fruiting bodies of the pathogen. Below the canker the tree may react by producing epicormic shoots. Non-lethal, superficial or callusing cankers on susceptible host trees are usually associated with mycovirus-induced hypovirulence. After the introduction of C. parasitica into a new area, eradication efforts by cutting and burning the infected plants/trees have mostly failed. In Europe, the mycovirus Cryphonectria hypovirus 1 (CHV-1) acts as a successful biological control agent of chestnut blight by causing so-called hypovirulence. CHV-1 infects C. parasitica and reduces its parasitic growth and sporulation capacity. Individual cankers can be therapeutically treated with hypovirus-infected C. parasitica strains. The hypovirus may subsequently spread to untreated cankers and become established in the C. parasitica population. Hypovirulence is present in many chestnut-growing regions of Europe, either resulting naturally or after biological control treatments. In North America, disease management of chestnut blight is mainly focused on breeding with the goal to backcross the Chinese chestnut's blight resistance into the American chestnut genome. © 2017 BSPP AND JOHN WILEY & SONS LTD.

[Studies on purification and properties of antagonistic protein from bacteria SS02 of Paenibacillus daejeonensis].

PubMed

Zhu, Kai; Zhang, Xiao-Yu; Ren, Zhi; Feng, Ding-Sheng; Wang, Yi-Ding

2007-07-01

The antifungal, anti-bacterical, anti-brine shrimp activities of SD22 isolated from Paenibacillus daejeonensis Bacteria SS02 were studied. The separation steps included ultracentrifugation, ultrafiltration and (NH4)2SO4 fractional precipitation, further purification was performed by SephadexG-75 and DEAE-32 chromatography. Its molecular weight determined by SDS-PAGE was 56.0 kD and its isoelectfic point was 6.4. SD22 was thermostable to some extent and stable to ultraviolet, but sensitive to some of the enzyme. SD22 could kill most pathogens from propagation, such as Rhizoctonia cerealis, Sclerotinia sclerotiorum Physalospora piricala, Trichodema viride, Gliocladium viride, Curvularia leaf spot, Fusarium sp, Fusarium head blight, Beauveria Bassiana, Escherichia coli, Staphylococcus aureus, Bacillus subtilis , Candidal vaginitis, Fusarium oxysporum Schl. emend. Sayder & Hansem et al. The results will be helpful to find out a novel antifungal protein.

Identification of quantitative trait loci (QTLs) responsible for sheath blight resistance in rice using recombinant inbred line population of Lemont X Jasmine 85

USDA-ARS?s Scientific Manuscript database

Rice sheath blight (RSB) caused by the soil borne pathogen Rhizoctonia solani, is one of the most destructive diseases of rice, causing severe losses in rice yield and quality annually. The major gene (s) governing the resistance to RSB have not been found in cultivated rice worldwide. However, ri...

Sweetgum blight and dieback of associated hardwoods on the Beltsville Experimental Forest in Maryland

Treesearch

R. H. Fenton; J. D. Diller

1960-01-01

In 1948, a dieback of sweetgum (Liquidambar styraciflua L.) was first observed and reported at College Park, Md. Since then, surveys made from Maryland southward have shown that the dieback, now termed sweetgum blight, has increased in both distribution and severity and now occurs throughout much of the species range. No pathogenic organism has been found to be...

A single effector protein, ArvRpt2ea from Erwinia amylovora, can cause fire blight disease symptons and induces salicylic acid dependent defense response

USDA-ARS?s Scientific Manuscript database

The AvrRpt2EA effector protein of Erwinia amylovora is important for pathogen recognition in the fire blight resistant crabapple Malus ×robusta 5; however, little is known about its role in susceptible apple genotypes. In order to study its function in planta, we expressed a plant optimized version...

Effect of polyacetylenic acids from Prunella vulgaris on various plant pathogens.

PubMed

Yoon, M-Y; Choi, G J; Choi, Y H; Jang, K S; Park, M S; Cha, B; Kim, J-C

2010-11-01

This study is aiming at characterizing antifungal substances from the methanol extract of Prunella vulgaris and at investigating those substances' antifungal and antioomycete activities against various plant pathogens. Two polyacetylenic acids were isolated from P. vulgaris as active principles and identified as octadeca-9,11,13-triynoic acid and trans-octadec-13-ene-9,11-diynoic acid. These two compounds inhibited the growth of Magnaporthe oryzae, Rhizoctonia solani, Phytophthora infestans, Sclerotinia sclerotiorum, Fusarium oxysporum f. sp. raphani, and Phytophthora capsici. In addition, these two compounds and the wettable powder-type formulation of an n-hexane fraction of P. vulgaris significantly suppressed the development of rice blast, tomato late blight, wheat leaf rust, and red pepper anthracnose. These data show that the extract of P. vulgaris and two polyacetylenic acids possess antifungal and antioomycete activities against a broad spectrum of tested plant pathogens. This is the first report on the occurrence of octadeca-9,11,13-triynoic acid and trans-octadec-13-ene-9,11-diynoic acid in P. vulgaris and their efficacy against plant diseases. The crude extract containing the two polyacetylenic acids can be used as a natural fungicide for the control of various plant diseases. © 2010 The Authors. © 2010 The Society for Applied Microbiology.

Volatiles produced by soil-borne endophytic bacteria increase plant pathogen resistance and affect tritrophic interactions

PubMed Central

Ton, Jurriaan; Brandenburg, Anna; Karlen, Danielle; Zopfi, Jakob; Turlings, Ted C. J.

2014-01-01

Volatile organic compounds (VOCs) released by soil microorganisms influence plant growth and pathogen resistance. Yet, very little is known about their influence on herbivores and higher trophic levels. We studied the origin and role of a major bacterial VOC, 2,3-butanediol (2,3-BD), on plant growth, pathogen and herbivore resistance, and the attraction of natural enemies in maize. One of the major contributors to 2,3-BD in the headspace of soil-grown maize seedlings was identified as Enterobacter aerogenes, an endophytic bacterium that colonizes the plants. The production of 2,3-BD by E. aerogenes rendered maize plants more resistant against the Northern corn leaf blight fungus Setosphaeria turcica. On the contrary, E. aerogenes-inoculated plants were less resistant against the caterpillar Spodoptera littoralis. The effect of 2,3-BD on the attraction of the parasitoid Cotesia marginiventris was more variable: 2,3-BD application to the headspace of the plants had no effect on the parasitoids, but application to the soil increased parasitoid attraction. Furthermore, inoculation of seeds with E. aerogenes decreased plant attractiveness, whereas inoculation of soil with a total extract of soil microbes increased parasitoid attraction, suggesting that the effect of 2,3-BD on the parasitoid is indirect and depends on the composition of the microbial community. PMID:24127750

Erwinia amylovora psychrotrophic adaptations: evidence of pathogenic potential and survival at temperate and low environmental temperatures.

PubMed

Santander, Ricardo D; Biosca, Elena G

2017-01-01

The fire blight pathogen Erwinia amylovora can be considered a psychrotrophic bacterial species since it can grow at temperatures ranging from 4 °C to 37 °C, with an optimum of 28 °C. In many plant pathogens the expression of virulence determinants is restricted to a certain range of temperatures. In the case of E. amylovora, temperatures above 18 °C are required for blossom blight epidemics under field conditions. Moreover, this bacterium is able to infect a variety of host tissues/organs apart from flowers, but it is still unknown how environmental temperatures, especially those below 18 °C, affect the pathogen ability to cause fire blight disease symptoms in such tissues/organs. There is also scarce information on how temperatures below 18 °C affect the E. amylovora starvation-survival responses, which might determine its persistence in the environment and probably contribute to the seasonal development of fire blight disease, as occurs in other pathogens. To characterize the virulence and survival of E. amylovora at temperate and low temperatures, we evaluated the effect of three temperatures (4 °C, 14 °C, 28 °C) on symptom development, and on different parameters linked to starvation and virulence. E. amylovora was pathogenic at the three assayed temperatures, with a slow-down of symptom development correlating with colder temperatures and slower growth rates. Siderophore secretion and motility also decreased in parallel to incubation temperatures. However, production of the exopolysaccharides amylovoran and levan was enhanced at 4 °C and 14 °C, respectively. Similarly, biofilm formation, and oxidative stress resistance were improved at 14 °C, with this temperature also favoring the maintenance of culturability, together with a reduction in cell size and the acquisition of rounded shapes in E. amylovora cells subjected to long-term starvation. However, starvation at 28 °C and 4 °C induced an enhanced viable but nonculturable (VBNC) response (to a lesser extent at 4 °C). This work reveals E. amylovora as a highly adaptable pathogen that retains its pathogenic potential even at the minimal growth temperatures, with an improved exopolysaccharide synthesis, biofilm formation or oxidative stress resistance at 14 °C, with respect to the optimal growth temperature (28 °C). Finally, our results also demonstrate the thermal modulation of starvation responses in E. amylovora, suggesting that the starvation-survival and the VBNC states are part of its life cycle. These results confirm the particular psychrotrophic adaptations of E. amylovora , revealing its pathogenic potential and survival at temperate and low environmental temperatures, which have probably contributed to its successful spread to countries with different climates. This knowledge might improve integrated control measures against fire blight.

Erwinia amylovora psychrotrophic adaptations: evidence of pathogenic potential and survival at temperate and low environmental temperatures

PubMed Central

Santander, Ricardo D.

2017-01-01

The fire blight pathogen Erwinia amylovora can be considered a psychrotrophic bacterial species since it can grow at temperatures ranging from 4 °C to 37 °C, with an optimum of 28 °C. In many plant pathogens the expression of virulence determinants is restricted to a certain range of temperatures. In the case of E. amylovora, temperatures above 18 °C are required for blossom blight epidemics under field conditions. Moreover, this bacterium is able to infect a variety of host tissues/organs apart from flowers, but it is still unknown how environmental temperatures, especially those below 18 °C, affect the pathogen ability to cause fire blight disease symptoms in such tissues/organs. There is also scarce information on how temperatures below 18 °C affect the E. amylovora starvation-survival responses, which might determine its persistence in the environment and probably contribute to the seasonal development of fire blight disease, as occurs in other pathogens. To characterize the virulence and survival of E. amylovora at temperate and low temperatures, we evaluated the effect of three temperatures (4 °C, 14 °C, 28 °C) on symptom development, and on different parameters linked to starvation and virulence. E. amylovora was pathogenic at the three assayed temperatures, with a slow-down of symptom development correlating with colder temperatures and slower growth rates. Siderophore secretion and motility also decreased in parallel to incubation temperatures. However, production of the exopolysaccharides amylovoran and levan was enhanced at 4 °C and 14 °C, respectively. Similarly, biofilm formation, and oxidative stress resistance were improved at 14 °C, with this temperature also favoring the maintenance of culturability, together with a reduction in cell size and the acquisition of rounded shapes in E. amylovora cells subjected to long-term starvation. However, starvation at 28 °C and 4 °C induced an enhanced viable but nonculturable (VBNC) response (to a lesser extent at 4 °C). This work reveals E. amylovora as a highly adaptable pathogen that retains its pathogenic potential even at the minimal growth temperatures, with an improved exopolysaccharide synthesis, biofilm formation or oxidative stress resistance at 14 °C, with respect to the optimal growth temperature (28 °C). Finally, our results also demonstrate the thermal modulation of starvation responses in E. amylovora, suggesting that the starvation-survival and the VBNC states are part of its life cycle. These results confirm the particular psychrotrophic adaptations of E. amylovora, revealing its pathogenic potential and survival at temperate and low environmental temperatures, which have probably contributed to its successful spread to countries with different climates. This knowledge might improve integrated control measures against fire blight. PMID:29085749

Insights into organ-specific pathogen defense responses in plants: RNA-seq analysis of potato tuber-Phytophthora infestans interactions.

PubMed

Gao, Liangliang; Tu, Zheng Jin; Millett, Benjamin P; Bradeen, James M

2013-05-23

The late blight pathogen Phytophthora infestans can attack both potato foliage and tubers. Although interaction transcriptome dynamics between potato foliage and various pathogens have been reported, no transcriptome study has focused specifically upon how potato tubers respond to pathogen infection. When inoculated with P. infestans, tubers of nontransformed 'Russet Burbank' (WT) potato develop late blight disease while those of transgenic 'Russet Burbank' line SP2211 (+RB), which expresses the potato late blight resistance gene RB (Rpi-blb1), do not. We compared transcriptome responses to P. infestans inoculation in tubers of these two lines. We demonstrated the practicality of RNA-seq to study tetraploid potato and present the first RNA-seq study of potato tuber diseases. A total of 483 million paired end Illumina RNA-seq reads were generated, representing the transcription of around 30,000 potato genes. Differentially expressed genes, gene groups and ontology bins that exhibited differences between the WT and +RB lines were identified. P. infestans transcripts, including those of known effectors, were also identified. Faster and stronger activation of defense related genes, gene groups and ontology bins correlate with successful tuber resistance against P. infestans. Our results suggest that the hypersensitive response is likely a general form of resistance against the hemibiotrophic P. infestans-even in potato tubers, organs that develop below ground.

Insights into organ-specific pathogen defense responses in plants: RNA-seq analysis of potato tuber-Phytophthora infestans interactions

PubMed Central

2013-01-01

Background The late blight pathogen Phytophthora infestans can attack both potato foliage and tubers. Although interaction transcriptome dynamics between potato foliage and various pathogens have been reported, no transcriptome study has focused specifically upon how potato tubers respond to pathogen infection. When inoculated with P. infestans, tubers of nontransformed ‘Russet Burbank’ (WT) potato develop late blight disease while those of transgenic ‘Russet Burbank’ line SP2211 (+RB), which expresses the potato late blight resistance gene RB (Rpi-blb1), do not. We compared transcriptome responses to P. infestans inoculation in tubers of these two lines. Results We demonstrated the practicality of RNA-seq to study tetraploid potato and present the first RNA-seq study of potato tuber diseases. A total of 483 million paired end Illumina RNA-seq reads were generated, representing the transcription of around 30,000 potato genes. Differentially expressed genes, gene groups and ontology bins that exhibited differences between the WT and +RB lines were identified. P. infestans transcripts, including those of known effectors, were also identified. Conclusion Faster and stronger activation of defense related genes, gene groups and ontology bins correlate with successful tuber resistance against P. infestans. Our results suggest that the hypersensitive response is likely a general form of resistance against the hemibiotrophic P. infestans—even in potato tubers, organs that develop below ground. PMID:23702331

Rhizosphaera Needle Disease of Fir

Treesearch

Mike Albers; Jana Albers; Jane Cummings-Carlson; Linda Haugen; Nancy Wenner

1996-01-01

Rhizosphaera pini is a common plant pathogen in the Lake States, Northeastern States and Canada. A closely related pathogen, Rhizosphaera kalkhoffii, causes a common needle blight on spruce and other conifers. R. pini is often considered to be a weak pathogen, occurring on stressed foliage or foliage killed by other causes. However, it has been observed causing...

Genome sequence of the necrotrophic plant pathogen Pythium ultimum reveals original pathogenicity mechanisms and effector repertoire.

USDA-ARS?s Scientific Manuscript database

The P. ultimum DAOM BR144 (=CBS 805.95 = ATCC200006) genome (42.8 Mb) encodes 15,290 genes, and has extensive sequence similarity and synteny with related Phytophthora spp., including the potato late blight pathogen Phytophthora infestans. Whole transcriptome sequencing revealed expression of 86 % o...

Population genomics of Fusarium graminearum reveals signatures of divergent evolution within a major cereal pathogen

USDA-ARS?s Scientific Manuscript database

The cereal pathogen Fusarium graminearum is the primary cause of Fusarium head blight (FHB) and a significant threat to food safety and crop production. To elucidate population structure and identify genomic targets of selection within major FHB pathogen populations in North America we sequenced the...

The genetic basis of flecking and its relationship to disease resistance in the IBM maize mapping population.

PubMed

Vontimitta, Vijay; Olukolu, Bode A; Penning, Bryan W; Johal, Gurmukh; Balint-Kurti, P J

2015-11-01

In this paper, we determine the genetic architecture controlling leaf flecking in maize and investigate its relationship to disease resistance and the defense response. Flecking is defined as a mild, often environmentally dependent lesion phenotype observed on the leaves of several commonly used maize inbred lines. Anecdotal evidence suggests a link between flecking and enhanced broad-spectrum disease resistance. Neither the genetic basis underlying flecking nor its possible relationship to disease resistance has been systematically evaluated. The commonly used maize inbred Mo17 has a mild flecking phenotype. The IBM-advanced intercross mapping population, derived from a cross between Mo17 and another commonly used inbred B73, has been used for mapping a number of traits in maize including several related to disease resistance. In this study, flecking was assessed in the IBM population over 6 environments. Several quantitative trait loci for flecking were identified, with the strongest one located on chromosome 6. Low but moderately significant correlations were observed between stronger flecking and higher disease resistance with respect to two diseases, southern leaf blight and northern leaf blight and between stronger flecking and a stronger defense response.

Anthracnose Diseases of Eastern Hardwoods

Treesearch

Frederick H. Berry

1985-01-01

Anthracnose diseases of hardwood trees are widespread throughout the Eastern United States. The most common symptom of these diseases is dead areas or blotches on the leaves. Because of the brown and black, scorched appearance of the leaves, the diseases are sometimes called leaf blight.

Improvement of the Efficacy of Linear Undecapeptides against Plant-Pathogenic Bacteria by Incorporation of d-Amino Acids ▿

PubMed Central

Güell, Imma; Cabrefiga, Jordi; Badosa, Esther; Ferre, Rafael; Talleda, Montserrat; Bardají, Eduard; Planas, Marta; Feliu, Lidia; Montesinos, Emilio

2011-01-01

A set of 31 undecapeptides, incorporating 1 to 11 d-amino acids and derived from the antimicrobial peptide BP100 (KKLFKKILKYL-NH2), was designed and synthesized. This set was evaluated for inhibition of growth of the plant-pathogenic bacteria Erwinia amylovora, Pseudomonas syringae pv. syringae, and Xanthomonas axonopodis pv. vesicatoria, hemolysis, and protease degradation. Two derivatives were as active as BP100, and 10 peptides displayed improved activity, with the all-d isomer being the most active. Twenty-six peptides were less hemolytic than BP100, and all peptides were more stable against protease degradation. Plant extracts inhibited the activity of BP100 as well as that of the d-isomers. Ten derivatives incorporating one d-amino acid each were tested in an infectivity inhibition assay with the three plant-pathogenic bacteria by using detached pear and pepper leaves and pear fruits. All 10 peptides studied were active against E. amylovora, 6 displayed activity against P. syringae pv. syringae, and 2 displayed activity against X. axonopodis pv. vesicatoria. Peptides BP143 (KKLFKKILKYL-NH2) and BP145 (KKLFKKILKYL-NH2), containing one d-amino acid at positions 4 and 2 (underlined), respectively, were evaluated in whole-plant assays for the control of bacterial blight of pepper and pear and fire blight of pear. Peptide BP143 was as effective as streptomycin in the three pathosystems, was more effective than BP100 against bacterial blight of pepper and pear, and equally effective against fire blight of pear. PMID:21335383

Antifungal, Mosquito Deterrent, and Larvicidal Activity of N-(benzylidene)-3-cyclohexylpropionic Acid Hydrazide Derivatives

DTIC Science & Technology

2013-01-01

chum sp.), Phomopsis and Botrytis diseases are serious problems of strawberry fruit in especially southeastern US N. Tabanca (&) A. Ali I. A...obscurans is a common fungus that causes leaf blight in strawberry and other plants, while P. viticola causes Phomopsis cane and leaf spot of grapes...The three Collet- otrichum species and P. obscurans were isolated from strawberry (Fragaria ananassa Duchesne), while P. viti- cola and B. cinerea were

Enhanced tomato disease resistance primed by arbuscular mycorrhizal fungus

PubMed Central

Song, Yuanyuan; Chen, Dongmei; Lu, Kai; Sun, Zhongxiang; Zeng, Rensen

2015-01-01

Roots of most terrestrial plants form symbiotic associations (mycorrhiza) with soil- borne arbuscular mycorrhizal fungi (AMF). Many studies show that mycorrhizal colonization enhances plant resistance against pathogenic fungi. However, the mechanism of mycorrhiza-induced disease resistance remains equivocal. In this study, we found that mycorrhizal inoculation with AMF Funneliformis mosseae significantly alleviated tomato (Solanum lycopersicum Mill.) early blight disease caused by Alternaria solani Sorauer. AMF pre-inoculation led to significant increases in activities of β-1,3-glucanase, chitinase, phenylalanine ammonia-lyase (PAL) and lipoxygenase (LOX) in tomato leaves upon pathogen inoculation. Mycorrhizal inoculation alone did not influence the transcripts of most genes tested. However, pathogen attack on AMF-inoculated plants provoked strong defense responses of three genes encoding pathogenesis-related proteins, PR1, PR2, and PR3, as well as defense-related genes LOX, AOC, and PAL, in tomato leaves. The induction of defense responses in AMF pre-inoculated plants was much higher and more rapid than that in un-inoculated plants in present of pathogen infection. Three tomato genotypes: a Castlemart wild-type (WT) plant, a jasmonate (JA) biosynthesis mutant (spr2), and a prosystemin-overexpressing 35S::PS plant were used to examine the role of the JA signaling pathway in AMF-primed disease defense. Pathogen infection on mycorrhizal 35S::PS plants led to higher induction of defense-related genes and enzymes relative to WT plants. However, pathogen infection did not induce these genes and enzymes in mycorrhizal spr2 mutant plants. Bioassays showed that 35S::PS plants were more resistant and spr2 plants were more susceptible to early blight compared with WT plants. Our finding indicates that mycorrhizal colonization enhances tomato resistance to early blight by priming systemic defense response, and the JA signaling pathway is essential for mycorrhiza-primed disease resistance. PMID:26442091

Enhanced tomato disease resistance primed by arbuscular mycorrhizal fungus.

PubMed

Song, Yuanyuan; Chen, Dongmei; Lu, Kai; Sun, Zhongxiang; Zeng, Rensen

2015-01-01

Roots of most terrestrial plants form symbiotic associations (mycorrhiza) with soil- borne arbuscular mycorrhizal fungi (AMF). Many studies show that mycorrhizal colonization enhances plant resistance against pathogenic fungi. However, the mechanism of mycorrhiza-induced disease resistance remains equivocal. In this study, we found that mycorrhizal inoculation with AMF Funneliformis mosseae significantly alleviated tomato (Solanum lycopersicum Mill.) early blight disease caused by Alternaria solani Sorauer. AMF pre-inoculation led to significant increases in activities of β-1,3-glucanase, chitinase, phenylalanine ammonia-lyase (PAL) and lipoxygenase (LOX) in tomato leaves upon pathogen inoculation. Mycorrhizal inoculation alone did not influence the transcripts of most genes tested. However, pathogen attack on AMF-inoculated plants provoked strong defense responses of three genes encoding pathogenesis-related proteins, PR1, PR2, and PR3, as well as defense-related genes LOX, AOC, and PAL, in tomato leaves. The induction of defense responses in AMF pre-inoculated plants was much higher and more rapid than that in un-inoculated plants in present of pathogen infection. Three tomato genotypes: a Castlemart wild-type (WT) plant, a jasmonate (JA) biosynthesis mutant (spr2), and a prosystemin-overexpressing 35S::PS plant were used to examine the role of the JA signaling pathway in AMF-primed disease defense. Pathogen infection on mycorrhizal 35S::PS plants led to higher induction of defense-related genes and enzymes relative to WT plants. However, pathogen infection did not induce these genes and enzymes in mycorrhizal spr2 mutant plants. Bioassays showed that 35S::PS plants were more resistant and spr2 plants were more susceptible to early blight compared with WT plants. Our finding indicates that mycorrhizal colonization enhances tomato resistance to early blight by priming systemic defense response, and the JA signaling pathway is essential for mycorrhiza-primed disease resistance.

Genetic control and combining ability of agronomic attributes and northern leaf blight-related attributes in popcorn.

PubMed

Santos, J S; Amaral Júnior, A T; Vivas, M; Mafra, G S; Pena, G F; Silva, F H L; Guimarães, A G

2017-09-27

The present study was conducted to investigate the genetic control and to estimate the general and specific combining abilities of popcorn for agronomic attributes and attributes related to resistance to northern leaf blight (NLB). The 56 hybrids (F 1 and reciprocals), together with the eight parent lines and six controls, were evaluated in two harvests, in a randomized-block design with four replications. Dominance components were more expressive than the additive components for grain yield and expression of resistance, and hybridization was the most suitable option for obtaining resistant and productive genotypes. For grain yield, popping expansion, and resistance to NLB, there was no significance for reciprocal effects, which indicates that the direction in which the cross is performed does not interfere with the hybrid's performance. Then, the superior hybrids recommended for more profitable growth were P8 x L61, L61 x L76, and L61 x L77.

SP-LL-37, human antimicrobial peptide, enhances disease resistance in transgenic rice.

PubMed

Lee, In Hye; Jung, Yu-Jin; Cho, Yong Gu; Nou, Ill Sup; Huq, Md Amdadul; Nogoy, Franz Marielle; Kang, Kwon-Kyoo

2017-01-01

Human LL-37 is a multifunctional antimicrobial peptide of cathelicidin family. It has been shown in recent studies that it can serve as a host's defense against influenza A virus. We now demonstrate in this study how signal peptide LL-37 (SP-LL-37) can be used in rice resistance against bacterial leaf blight and blast. We synthesized LL-37 peptide and subcloned in a recombinant pPZP vector with pGD1 as promoter. SP-LL-37 was introduced into rice plants by Agrobacterium mediated transformation. Stable expression of SP-LL-37 in transgenic rice plants was confirmed by RT-PCR and ELISA analyses. Subcellular localization of SP-LL-37-GFP fusion protein showed evidently in intercellular space. Our data on testing for resistance to bacterial leaf blight and blast revealed that the transgenic lines are highly resistant compared to its wildtype. Our results suggest that LL-37 can be further explored to improve wide-spectrum resistance to biotic stress in rice.

Monitoring the efficacy of mutated Allium sativum leaf lectin in transgenic rice against Rhizoctonia solani.

PubMed

Ghosh, Prithwi; Sen, Senjuti; Chakraborty, Joydeep; Das, Sampa

2016-03-01

Rice sheath blight, caused by Rhizoctonia solani is one of the most devastating diseases of rice. It is associated with significant reduction in rice productivity worldwide. A mutant variant of mannose binding Allium sativum leaf agglutinin (mASAL) was previously reported to exhibit strong antifungal activity against R. solani. In this study, the mASAL gene has been evaluated for its in planta antifungal activity in rice plants. mASAL was cloned into pCAMBIA1301 binary vector under the control of CaMV35S promoter. It was expressed in an elite indica rice cv. IR64 by employing Agrobacterium tumefaciens-mediated transformation. Molecular analyses of transgenic plants confirmed the presence and stable integration of mASAL gene. Immunohistofluorescence analysis of various tissue sections of plant parts clearly indicated the constitutive expression of mASAL. The segregation pattern of mASAL transgene was observed in T1 progenies in a 3:1 Mendelian ratio. The expression of mASAL was confirmed in T0 and T1 plants through western blot analysis followed by ELISA. In planta bioassay of transgenic lines against R. solani exhibited an average of 55 % reduction in sheath blight percentage disease index (PDI). The present study opens up the possibility of engineering rice plants with the antifungal gene mASAL, conferring resistance to sheath blight.

Ascochyta blight of chickpea: production of phytotoxins and disease management.

PubMed

Shahid, Ahmad Ali; Husnain, Tayyab; Riazuddin, Sheikh

2008-01-01

Ascochyta blight caused by Ascochyta rabiei (Pass.) Lab., is the most devastating disease of chickpea and can occur anywhere the crop is grown. Several epidemics of blight causing complete yield losses have been reported. Despite extensive pathological and molecular studies, the nature and extent of pathogenic variability in A. rabiei have not been clearly established. Several isolates of A. rabiei were grown in liquid culture medium which secreted phytotoxic compounds of solanapyrone A, B, C and cytochalasin D. The same fungal metabolites were also recovered from extract of naturally blight stricken chickpea plants. Toxicity of purified solanapyrones as determined by cell bioassay was in the order of solanapyrone A>solanapyrone B>solanapyrone C. However, the specificity of all three compounds was dependent on the genetic identity of the chickpea cultivars. Seed treatment and foliar application of fungicides are commonly recommended for disease management, but further information on biology and survival of A. rabiei is needed to devise more effective management strategies. A short description of chickpea blight, geographical distribution, disease cycle, symptoms, losses, production of phytotoxins and disease management practices for the control of Ascochyta blight will be discussed in this review article.

A cellulose binding domain protein restores female fertility when expressed in transgenic Bintje potato.

PubMed

Jones, Richard W; Perez, Frances G

2016-03-18

Expression of a gene encoding the family 1 cellulose binding domain protein CBD1, identified in the cellulosic cell wall of the potato late blight pathogen Phytophthora infestans, was tested in transgenic potato to determine if it had an influence on plant cell walls and resistance to late blight. Multiple regenerants of potato (cv. Bintje) were developed and selected for high expression of CBD 1 transcripts. Tests with detached leaflets showed no evidence of increased or decreased resistance to P. infestans, in comparison with the blight susceptible Bintje controls, however, changes in plant morphology were evident in CBD 1 transgenics. Plant height increases were evident, and most importantly, the ability to produce seed berries from a previously sterile cultivar. Immunolocalization of CBD 1 in seed berries revealed the presence throughout the tissue. While Bintje control plants are male and female sterile, CBD 1 transgenics were female fertile. Crosses made using pollen from the late blight resistant Sarpo Mira and transgenic CBD1 Bintje as the female parent demonstrated the ability to introgress P. infestans targeted resistance genes, as well as genes responsible for color and tuber shape, into Bintje germplasm. A family 1 cellulose-binding domain (CBD 1) encoding gene from the potato late blight pathogen P. infestans was used to develop transgenic Bintje potato plants. Transgenic plants became female fertile, allowing for a previously sterile cultivar to be used in breeding improvement. Selection for the absence of the CBD transgene in progeny should allow for immediate use of a genetically enhanced material. Potential for use in other Solanaceous crops is proposed.

Environmental factors impact Passalora sequoiae conidia counts from Leyland Cypress

USDA-ARS?s Scientific Manuscript database

Needle blight disease, caused by Passalora sequoiae, results in a progressive lost of leaf tissue on Leyland cypress (×Cupressocyparis leylandii) within container and field tree nurseries, in the landscape, and on Christmas tree farms. Fungicide schedules were developed in response to seasonal sympt...

Differential aggressiveness of Bipolaris microstegii and B. drechsleri on Japanese Stiltgrass

USDA-ARS?s Scientific Manuscript database

Six populations of Japanese stiltgrass (JSG, Microstegium vimineum) were tested for susceptibility to both Bipolaris microstegii (5 isolates) and B. drechsleri (3 isolates), each capable of causing severe leaf blight disease in the field and each with potential for biological control of this species...

[Effect of biopesticide Pythium oligandrum broth on gummy stem blight in cucumber seedlings, animal health and plant growth].

PubMed

Geng, Mingming; Jia, Ruilian; Sui, Zongming; Huang, Jianguo

2016-07-04

Biopesticides are safe and environment friendly. We evaluated the biocontrol effect of Pythium oligandrum broth (POB) and its toxicity to animals and plant growth. Animal, antagonist, pot, and field experiments with mice, Mycosphaerella melonis, and cucumber seedlings were carried out to study animal toxicity, control of gummy stem blight, plant growth, fruit yield and quality with POB produced from self-isolated P. oligandrum CQ2010. Mouse showed normal weight, appearances, performances and no pathogenic changes in organs and tissues with a large amount of POB supplied by lavage. The inhibition rate of POB against M. melonis was 51.95%, similar to thiophanate methy (800 times dilution) but much higher than chlorothalonil (200 times dilution). Malondialdehyde concentration was reduced whereas activities of peroxidase and superoxide dismutase were stimulated in seedling leaves irrespective of POB supplied before and after pathogenic inoculation. POB also decreased the pathogenic incidence and disease index with relative control efficacy from 54.8% to 64.1%. Thus, POB could alleviate cell membrane damage caused by pathogenic microbes, stimulate physiological reactions related to disease defense, and increase disease-resistant abilities of plants. Moreover, POB increased chlorophyll content, root activity, and uptake of nitrogen, phosphorus and potassium, resulting in growth acceleration, fruit yield increment, and quality improvement. POB is safe to animals and could control gummy stem blight of cucumber seedlings, promote plant growth, increase fruit yield, and improve the qualities.

Genome-Wide Linkage and Association Mapping of Halo Blight Resistance in Common Bean to Race 6 of the Globally Important Bacterial Pathogen

PubMed Central

Tock, Andrew J.; Fourie, Deidré; Walley, Peter G.; Holub, Eric B.; Soler, Alvaro; Cichy, Karen A.; Pastor-Corrales, Marcial A.; Song, Qijian; Porch, Timothy G.; Hart, John P.; Vasconcellos, Renato C. C.; Vicente, Joana G.; Barker, Guy C.; Miklas, Phillip N.

2017-01-01

Pseudomonas syringae pv. phaseolicola (Psph) Race 6 is a globally prevalent and broadly virulent bacterial pathogen with devastating impact causing halo blight of common bean (Phaseolus vulgaris L.). Common bean lines PI 150414 and CAL 143 are known sources of resistance against this pathogen. We constructed high-resolution linkage maps for three recombinant inbred populations to map resistance to Psph Race 6 derived from the two common bean lines. This was complemented with a genome-wide association study (GWAS) of Race 6 resistance in an Andean Diversity Panel of common bean. Race 6 resistance from PI 150414 maps to a single major-effect quantitative trait locus (QTL; HB4.2) on chromosome Pv04 and confers broad-spectrum resistance to eight other races of the pathogen. Resistance segregating in a Rojo × CAL 143 population maps to five chromosome arms and includes HB4.2. GWAS detected one QTL (HB5.1) on chromosome Pv05 for resistance to Race 6 with significant influence on seed yield. The same HB5.1 QTL, found in both Canadian Wonder × PI 150414 and Rojo × CAL 143 populations, was effective against Race 6 but lacks broad resistance. This study provides evidence for marker-assisted breeding for more durable halo blight control in common bean by combining alleles of race-nonspecific resistance (HB4.2 from PI 150414) and race-specific resistance (HB5.1 from cv. Rojo). PMID:28736566

Proteomics analysis suggests broad functional changes in potato leaves triggered by phosphites and a complex indirect mode of action against Phytophthora infestans.

PubMed

Lim, Sanghyun; Borza, Tudor; Peters, Rick D; Coffin, Robert H; Al-Mughrabi, Khalil I; Pinto, Devanand M; Wang-Pruski, Gefu

2013-11-20

Phosphite (salts of phosphorous acid; Phi)-based fungicides are increasingly used in controlling oomycete pathogens, such as the late blight agent Phytophthora infestans. In plants, low amounts of Phi induce pathogen resistance through an indirect mode of action. We used iTRAQ-based quantitative proteomics to investigate the effects of phosphite on potato plants before and after infection with P. infestans. Ninety-three (62 up-regulated and 31 down-regulated) differentially regulated proteins, from a total of 1172 reproducibly identified proteins, were identified in the leaf proteome of Phi-treated potato plants. Four days post-inoculation with P. infestans, 16 of the 31 down-regulated proteins remained down-regulated and 42 of the 62 up-regulated proteins remained up-regulated, including 90% of the defense proteins. This group includes pathogenesis-related, stress-responsive, and detoxification-related proteins. Callose deposition and ultrastructural analyses of leaf tissues after infection were used to complement the proteomics approach. This study represents the first comprehensive proteomics analysis of the indirect mode of action of Phi, demonstrating broad effects on plant defense and plant metabolism. The proteomics data and the microscopy study suggest that Phi triggers a hypersensitive response that is responsible for induced resistance of potato leaves against P. infestans. Phosphie triggers complex functional changes in potato leaves that are responsible for the induced resistance against Phytophthora infestans. This article is part of a Special Issue entitled: Translational Plant Proteomics. Copyright © 2013 Elsevier B.V. All rights reserved.

Sarcococca blight: Use of whole genome sequencing as a strategy for fungal disease diagnosis

USDA-ARS?s Scientific Manuscript database

Early and accurate diagnosis of new plant pathogens is vital for the rapid implementation of effective mitigation strategies and appropriate regulatory responses. Most commonly, pathogen identification relies on morphology and DNA marker analysis. However, for new diseases, these approaches may not...

Potato agriculture, late blight science, and the molecularization of plant pathology.

PubMed

Turner, R Steven

2008-01-01

By the mid-1980s nucleic-acid based methods were penetrating the farthest reaches of biological science, triggering rivalries among practitioners, altering relationships among subfields, and transforming the research front. This article delivers a "bottom up" analysis of that transformation at work in one important area of biological science, plant pathology, by tracing the "molecularization" of efforts to understand and control one notorious plant disease -- the late blight of potatoes. It mobilizes the research literature of late blight science as a tool through which to trace the changing typography of the research front from 1983 to 2003. During these years molecularization intensified the traditional fragmentation of the late blight research community, even as it dramatically integrated study of the causal organism into broader areas of biology. In these decades the pathogen responsible for late blight, the oomycete "Phytophthora infestans," was discovered to be undergoing massive, frightening, and still largely unexplained genetic diversification -- a circumstance that lends the episode examined here an urgency that reinforces its historiographical significance as a case-study in the molecularization of the biological sciences.

A rapid lateral-flow immunoassay for phytosanitary detection of Erwinia amylovora and on-site fire blight diagnosis.

PubMed

Braun-Kiewnick, A; Altenbach, D; Oberhänsli, T; Bitterlin, W; Duffy, B

2011-10-01

Fire blight is an invasive disease caused by Erwinia amylovora that threatens pome fruit production globally. Effective implementation of phytosanitary control measures depends upon rapid, reliable pathogen detection and disease diagnosis. We developed a lateral-flow immunoassay specific for E. amylovora with a detection limit of log 5.7 CFU/ml, typical of pathogen concentrations in symptomatic plant material. The simple assay had comparable sensitivity to standard culture plating, serum agglutination and nested PCR when validated for application in a phytosanitary laboratory as a confirmatory test of cultured isolates and for first-line diagnosis of phytosanitary samples that represent the full range of commercial, ornamental and forestry host species. On-site validation in ring-trials with local plant inspectors demonstrated robust and reliable detection (compared to subsequent plating and PCR analysis). The simplicity, inspector acceptance and facilitation of expedited diagnosis (from 2 days for laboratory submitted samples to 15 min with the immunoassay), offers a valuable tool for improved phytosanitary control of fire blight. Copyright © 2011 Elsevier B.V. All rights reserved.

[Polyvalence of bacteriophages isolated from fruit trees, affected by bacterial fire blight].

PubMed

Tovkach, F I; Moroz, S N; Korol', N A; Faĭdiuk, Iu V; Kushkina, A I

2013-01-01

Phage populations appearing as a result of a pathogenic process caused by Erwinia amylovora have been discovered and described. They accompany bacterial fire blight development in the process of quince, pear and apple trees vegetation in Zakarpattya region of Ukraine. Phage isolates of the affected pear and quince include polyvalent virulent phages able to develop on bacterial strains associated with plants--E. amylovora. E. "horticola" and Pantoea agglomerans. E. amylovora isolated from the plant tissues affected by the fire blight and detected at the same time as phages proved to be resistant to the viral infection. It is hard to explain now this characteristic however it was noticed that resistance to phages can change drastically in case of dissociation, lysogenization and mutagenesis of erwinia in laboratory conditions. Phage population study shows that they are heterogeneous and can obviously include not only polyvalent but also specific viruses. Further studies of biology and molecular genetics of pure lines of isolated phages will help to get closer to understanding the place and role of bacteriophages in the complicated network of relations between bacterial pathogens and plants.

Stable expression and phenotypic impact of attacin E transgene in orchard grown apple trees over a 12 year period.

PubMed

Borejsza-Wysocka, Ewa; Norelli, John L; Aldwinckle, Herb S; Malnoy, Mickael

2010-06-03

Transgenic trees currently are being produced by Agrobacterium-mediated transformation and biolistics. The future use of transformed trees on a commercial basis depends upon thorough evaluation of the potential environmental and public health risk of the modified plants, transgene stability over a prolonged period of time and the effect of the gene on tree and fruit characteristics. We studied the stability of expression and the effect on resistance to the fire blight disease of the lytic protein gene, attacin E, in the apple cultivar 'Galaxy' grown in the field for 12 years. Using Southern and western blot analysis, we compared transgene copy number and observed stability of expression of this gene in the leaves and fruit in several transformed lines during a 12 year period. No silenced transgenic plant was detected. Also the expression of this gene resulted in an increase in resistance to fire blight throughout 12 years of orchard trial and did not affect fruit shape, size, acidity, firmness, weight or sugar level, tree morphology, leaf shape or flower morphology or color compared to the control. Overall, these results suggest that transgene expression in perennial species, such as fruit trees, remains stable in time and space, over extended periods and in different organs. This report shows that it is possible to improve a desirable trait in apple, such as the resistance to a pathogen, through genetic engineering, without adverse alteration of fruit characteristics and tree shape.

Evidence that the Ceratobasidium-like white-thread blight and black rot fungal pathogens from persimmon and tea crops in the Brazilian Atlantic Forest agroecosystem are two distinct phylospecies.

PubMed

Ceresini, Paulo C; Costa-Souza, Elaine; Zala, Marcello; Furtado, Edson L; Souza, Nilton L

2012-04-01

The white-thread blight and black rot (WTBR) caused by basidiomycetous fungi of the genus Ceratobasidium is emerging as an important plant disease in Brazil, particularly for crop species in the Ericales such as persimmon (Diospyros kaki) and tea (Camellia sinensis). However, the species identity of the fungal pathogen associated with either of these hosts is still unclear. In this work, we used sequence variation in the internal transcribed spacer regions, including the 5.8S coding region of rDNA (ITS-5.8S rDNA), to determine the phylogenetic placement of the local white-thread-blight-associated populations of Ceratobasidium sp. from persimmon and tea, in relation to Ceratobasidium species already described world-wide. The two sister populations of Ceratobasidium sp. from persimmon and tea in the Brazilian Atlantic Forest agroecosystem most likely represent distinct species within Ceratobasidium and are also distinct from C. noxium, the etiological agent of the first description of white-thread blight disease that was reported on coffee in India. The intraspecific variation for the two Ceratobasidium sp. populations was also analyzed using three mitochondrial genes (ATP6, nad1 and nad2). As reported for other fungi, variation in nuclear and mitochondrial DNA was incongruent. Despite distinct variability in the ITS-rDNA region these two populations shared similar mitochondrial DNA haplotypes.

Diseases of Landscape Ornamentals. Slide Script.

ERIC Educational Resources Information Center

Powell, Charles C.; Sydnor, T. Davis

This slide script, part of a series of slide scripts designed for use in vocational agriculture classes, deals with recognizing and controlling diseases found on ornamental landscape plants. Included in the script are narrations for use with a total of 80 slides illustrating various foliar diseases (anthracnose, black spot, hawthorn leaf blight,…

Gene expression profiling of the plant pathogenic basidiomycetous fungus Rhizoctonia solani AG 4 reveals putative virulence factors

USDA-ARS?s Scientific Manuscript database

Rhizoctonia solani is a ubiquitous basidiomycetous soilborne fungal pathogen causing damping off of seedlings, aerial blights and postharvest diseases. To gain insight into the molecular mechanisms of pathogenesis a global approach based on analysis of expressed sequence tags (ESTs) was undertaken. ...

Characterization of stuA mutants in the mycotoxigenic maize pathogen Fusarium verticillioides

USDA-ARS?s Scientific Manuscript database

Fusarium verticillioides is a major pathogen of maize, causing root, stalk and ear rots and seedling blight. It also produces fumonisin mycotoxins. Ingestion of fumonisin-contaminated corn causes acute toxicity in livestock and is a potential carcinogen to humans. StuA, an APSES protein class transc...

Nitric oxide detoxification by Fusarium verticillioides flavohemoglobin and role in pathogenicity of maize

USDA-ARS?s Scientific Manuscript database

Fusarium verticillioides is a non-obligate plant pathogen of maize causing a number of specific diseases, including root rot, kernel rot, seed rot, stalk rot, and seedling blight. The saprophytic nature of this fungus, its production of the mycotoxin fumonisin, and complex relationship maize puts t...

A Review of the Interactions between Wheat and Wheat Pathogens: Zymoseptoria tritici, Fusarium spp. and Parastagonospora nodorum

PubMed Central

Duba, Adrian; Goriewa-Duba, Klaudia; Wachowska, Urszula

2018-01-01

Zymoseptoria tritici is a hemibiotrophic pathogen which causes Septoria leaf blotch in wheat. The pathogenesis of the disease consists of a biotrophic phase and a necrotrophic phase. The pathogen infects the host plant by suppressing its immune response in the first stage of infection. Hemibiotrophic pathogens of the genus Fusarium cause Fusarium head blight, and the necrotrophic Parastagonospora nodorum is responsible for Septoria nodorum blotch in wheat. Cell wall-degrading enzymes in plants promote infections by necrotrophic and hemibiotrophic pathogens, and trichothecenes, secondary fungal metabolites, facilitate infections caused by fungi of the genus Fusarium. There are no sources of complete resistance to the above pathogens in wheat. Defense mechanisms in wheat are controlled by many genes encoding resistance traits. In the wheat genome, the characteristic features of loci responsible for resistance to pathogenic infections indicate that at least several dozen genes encode resistance to pathogens. The molecular interactions between wheat and Z. tritici, P. nodorum and Fusarium spp. pathogens have been insufficiently investigated. Most studies focus on the mechanisms by which the hemibiotrophic Z. tritici suppresses immune responses in plants and the role of mycotoxins and effector proteins in infections caused by P. nodorum and Fusarium spp. fungi. Trichothecene glycosylation and effector proteins, which are involved in defense responses in wheat, have been described at the molecular level. Recent advances in molecular biology have produced interesting findings which should be further elucidated in studies of molecular interactions between wheat and fungal pathogens. The Clustered Regularly-Interspaced Short Palindromic Repeats/ CRISPR associated (CRISPR/Cas) system can be used to introduce targeted mutations into the wheat genome and confer resistance to selected fungal diseases. Host-induced gene silencing and spray-induced gene silencing are also useful tools for analyzing wheat–pathogens interactions which can be used to develop new strategies for controlling fungal diseases. PMID:29642627

Defense Response and Suppression of Phytophthora Blight Disease of Pepper by Water Extract from Spent Mushroom Substrate of Lentinula edodes

PubMed Central

Kang, Dae-Sun; Min, Kyong-Jin; Kwak, A-Min; Lee, Sang-Yeop; Kang, Hee-Wan

2017-01-01

The spent mushroom substrate (SMS) of Lentinula edodes that was derived from sawdust bag cultivation was used as materials for controlling Phytophthora blight disease of pepper. Water extract from SMS (WESMS) of L. edodes inhibited mycelial growth of Phytophthora capsici, suppressed Phytophthora blight disease of pepper seedlings by 65% and promoted growth of the plant over 30%. In high performance liquid chromatography (HPLC) analysis, oxalic acid was detected as the main organic acid compound in WESMS and inhibited the fungal mycelium at a minimum concentration of 200 mg/l. In quantitative real-time PCR, the transcriptional expression of CaBPR1 (PR protein 1), CaBGLU (β-1,3-glucanase), CaPR-4 (PR protein 4), and CaPR-10 (PR protein 10) were significantly enhanced on WESMS and DL-β-aminobutyric acid (BABA) treated pepper leaves. In addition, the salicylic acid content was also increased 4 to 6 folds in the WESMS and BABA treated pepper leaves compared to water treated leaf sample. These findings suggest that WESMS of L. edodes suppress Phytophthora blight disease of pepper through multiple effects including antifungal activity, plant growth promotion, and defense gene induction. PMID:28592945

Defense Response and Suppression of Phytophthora Blight Disease of Pepper by Water Extract from Spent Mushroom Substrate of Lentinula edodes.

PubMed

Kang, Dae-Sun; Min, Kyong-Jin; Kwak, A-Min; Lee, Sang-Yeop; Kang, Hee-Wan

2017-06-01

The spent mushroom substrate (SMS) of Lentinula edodes that was derived from sawdust bag cultivation was used as materials for controlling Phytophthora blight disease of pepper. Water extract from SMS (WESMS) of L. edodes inhibited mycelial growth of Phytophthora capsici , suppressed Phytophthora blight disease of pepper seedlings by 65% and promoted growth of the plant over 30%. In high performance liquid chromatography (HPLC) analysis, oxalic acid was detected as the main organic acid compound in WESMS and inhibited the fungal mycelium at a minimum concentration of 200 mg/l. In quantitative real-time PCR, the transcriptional expression of CaBPR1 (PR protein 1), CaBGLU (β-1,3-glucanase), CaPR-4 (PR protein 4), and CaPR-10 (PR protein 10) were significantly enhanced on WESMS and DL-β-aminobutyric acid (BABA) treated pepper leaves. In addition, the salicylic acid content was also increased 4 to 6 folds in the WESMS and BABA treated pepper leaves compared to water treated leaf sample. These findings suggest that WESMS of L. edodes suppress Phytophthora blight disease of pepper through multiple effects including antifungal activity, plant growth promotion, and defense gene induction.

New Multilocus Variable-Number Tandem-Repeat Analysis Tool for Surveillance and Local Epidemiology of Bacterial Leaf Blight and Bacterial Leaf Streak of Rice Caused by Xanthomonas oryzae

PubMed Central

Poulin, L.; Grygiel, P.; Magne, M.; Rodriguez-R, L. M.; Forero Serna, N.; Zhao, S.; El Rafii, M.; Dao, S.; Tekete, C.; Wonni, I.; Koita, O.; Pruvost, O.; Verdier, V.; Vernière, C.

2014-01-01

Multilocus variable-number tandem-repeat analysis (MLVA) is efficient for routine typing and for investigating the genetic structures of natural microbial populations. Two distinct pathovars of Xanthomonas oryzae can cause significant crop losses in tropical and temperate rice-growing countries. Bacterial leaf streak is caused by X. oryzae pv. oryzicola, and bacterial leaf blight is caused by X. oryzae pv. oryzae. For the latter, two genetic lineages have been described in the literature. We developed a universal MLVA typing tool both for the identification of the three X. oryzae genetic lineages and for epidemiological analyses. Sixteen candidate variable-number tandem-repeat (VNTR) loci were selected according to their presence and polymorphism in 10 draft or complete genome sequences of the three X. oryzae lineages and by VNTR sequencing of a subset of loci of interest in 20 strains per lineage. The MLVA-16 scheme was then applied to 338 strains of X. oryzae representing different pathovars and geographical locations. Linkage disequilibrium between MLVA loci was calculated by index association on different scales, and the 16 loci showed linear Mantel correlation with MLSA data on 56 X. oryzae strains, suggesting that they provide a good phylogenetic signal. Furthermore, analyses of sets of strains for different lineages indicated the possibility of using the scheme for deeper epidemiological investigation on small spatial scales. PMID:25398857

Complete genome sequence of the fire blight pathogen Erwinia pyrifoliae DSM 12163T and comparative genomic insights into plant pathogenicity

PubMed Central

2010-01-01

Background Erwinia pyrifoliae is a newly described necrotrophic pathogen, which causes fire blight on Asian (Nashi) pear and is geographically restricted to Eastern Asia. Relatively little is known about its genetics compared to the closely related main fire blight pathogen E. amylovora. Results The genome of the type strain of E. pyrifoliae strain DSM 12163T, was sequenced using both 454 and Solexa pyrosequencing and annotated. The genome contains a circular chromosome of 4.026 Mb and four small plasmids. Based on their respective role in virulence in E. amylovora or related organisms, we identified several putative virulence factors, including type III and type VI secretion systems and their effectors, flagellar genes, sorbitol metabolism, iron uptake determinants, and quorum-sensing components. A deletion in the rpoS gene covering the most conserved region of the protein was identified which may contribute to the difference in virulence/host-range compared to E. amylovora. Comparative genomics with the pome fruit epiphyte Erwinia tasmaniensis Et1/99 showed that both species are overall highly similar, although specific differences were identified, for example the presence of some phage gene-containing regions and a high number of putative genomic islands containing transposases in the E. pyrifoliae DSM 12163T genome. Conclusions The E. pyrifoliae genome is an important addition to the published genome of E. tasmaniensis and the unfinished genome of E. amylovora providing a foundation for re-sequencing additional strains that may shed light on the evolution of the host-range and virulence/pathogenicity of this important group of plant-associated bacteria. PMID:20047678

Conservation of Erwinia amylovora pathogenicity-relevant genes among Erwinia genomes.

PubMed

Borruso, Luigimaria; Salomone-Stagni, Marco; Polsinelli, Ivan; Schmitt, Armin Otto; Benini, Stefano

2017-12-01

The Erwinia genus comprises species that are plant pathogens, non-pathogen, epiphytes, and opportunistic human pathogens. Within the genus, Erwinia amylovora ranks among the top 10 plant pathogenic bacteria. It causes the fire blight disease and is a global threat to commercial apple and pear production. We analyzed the presence/absence of the E. amylovora genes reported to be important for pathogenicity towards Rosaceae within various Erwinia strains genomes. This simple bottom-up approach, allowed us to correlate the analyzed genes to pathogenicity, host specificity, and make useful considerations to drive targeted studies.

Pathogenicity and infection strategies of the fire blight pathogen Erwinia amylovora in Rosaceae: state of the art.

PubMed

Vrancken, K; Holtappels, M; Schoofs, H; Deckers, T; Valcke, R

2013-05-01

Plants are host to a large amount of pathogenic bacteria. Fire blight, caused by the bacterium Erwinia amylovora, is an important disease in Rosaceae. Pathogenicity of E. amylovora is greatly influenced by the production of exopolysaccharides, such as amylovoran, and the use of the type III secretion system, which enables bacteria to penetrate host tissue and cause disease. When infection takes place, plants have to rely on the ability of each cell to recognize the pathogen and the signals emanating from the infection site in order to generate several defence mechanisms. These mechanisms consist of physical barriers and the production of antimicrobial components, both in a preformed and an inducible manner. Inducible defence responses are activated upon the recognition of elicitor molecules by plant cell receptors, either derived from invading micro-organisms or from pathogen-induced degradation of plant tissue. This recognition event triggers a signal transduction cascade, leading to a range of defence responses [reactive oxygen species (ROS), plant hormones, secondary metabolites, …] and redeployment of cellular energy in a fast, efficient and multiresponsive manner, which prevents further pathogen ingress. This review highlights the research that has been performed during recent years regarding this specific plant-pathogen interaction between Erwinia amylovora and Rosaceae, with a special emphasis on the pathogenicity and the infection strategy of E. amylovora and the possible defence mechanisms of the plant against this disease.

Shared flowering phenology, insect pests, and pathogens among wild, weedy, and cultivated rice in the Mekong Delta, Vietnam: implications for transgenic rice.

PubMed

Cohen, Michael B; Arpaia, Salvatore; Lan, La Pham; Chau, Luong Minh; Snow, Allison A

2008-01-01

Many varieties of transgenic rice are under development in countries where wild and weedy relatives co-occur with the crop. To evaluate possible risks associated with pollen-mediated transgene dispersal, we conducted a two-year survey in Vietnam to examine overlapping flowering periods of rice (Oryza sativa L.), weedy rice (O. sativa), and wild rice (O. rufipogon Griff.), all of which are inter-fertile. We surveyed populations in two regions of the Mekong Delta, northern and southern, and at three sites in each of three habitats per region: fresh water, saline water, and acid sulfate soil. Weedy rice frequently flowered simultaneously with neighboring cultivated rice plants. Flowering was more seasonal in wild rice and often peaked in November and December. Peak flowering times of wild rice overlapped with adjacent rice fields at all of the saline sites and half of the acid sulfate sites. The longer flowering season of wild rice ensured that crop-to-wild gene flow was possible in fresh water habitats as well. Our second objective was to determine whether wild and weedy rice populations are exposed to pests that could be targeted by future transgenes, which may then provide fitness benefits. These populations shared many pathogen and insect herbivore species with cultivated rice (leaffolder, locust, cricket, planthoppers, rice bug, stem borer, sheath blight, blast, bacterial leaf blight, and brown spot). Damage by leaffolders and locusts was the most frequently observed insect feeding damage on all three rice types. Indicator species analysis revealed that most of the insect herbivores were associated with particular habitats, demonstrating the importance of broad geographic sampling for transgenic rice risk assessment. These survey data and the strong likelihood of gene flow from cultivated rice suggest that further studies are needed to examine the effects of transgenic traits such as resistance to pests on the abundance of wild and weedy rice.

Transcriptome analysis of root response to citrus blight based on the newly assembled Swingle citrumelo draft genome.

PubMed

Zhang, Yunzeng; Barthe, Gary; Grosser, Jude W; Wang, Nian

2016-07-08

Citrus blight is a citrus tree overall decline disease and causes serious losses in the citrus industry worldwide. Although it was described more than one hundred years ago, its causal agent remains unknown and its pathophysiology is not well determined, which hampers our understanding of the disease and design of suitable disease management. In this study, we sequenced and assembled the draft genome for Swingle citrumelo, one important citrus rootstock. The draft genome is approximately 280 Mb, which covers 74 % of the estimated Swingle citrumelo genome and the average coverage is around 15X. The draft genome of Swingle citrumelo enabled us to conduct transcriptome analysis of roots of blight and healthy Swingle citrumelo using RNA-seq. The RNA-seq was reliable as evidenced by the high consistence of RNA-seq analysis and quantitative reverse transcription PCR results (R(2) = 0.966). Comparison of the gene expression profiles between blight and healthy root samples revealed the molecular mechanism underneath the characteristic blight phenotypes including decline, starch accumulation, and drought stress. The JA and ET biosynthesis and signaling pathways showed decreased transcript abundance, whereas SA-mediated defense-related genes showed increased transcript abundance in blight trees, suggesting unclassified biotrophic pathogen was involved in this disease. Overall, the Swingle citrumelo draft genome generated in this study will advance our understanding of plant biology and contribute to the citrus breeding. Transcriptome analysis of blight and healthy trees deepened our understanding of the pathophysiology of citrus blight.

StWRKY8 transcription factor regulates benzylisoquinoline alkaloid pathway in potato conferring resistance to late blight.

PubMed

Yogendra, Kalenahalli N; Dhokane, Dhananjay; Kushalappa, Ajjamada C; Sarmiento, Felipe; Rodriguez, Ernesto; Mosquera, Teresa

2017-03-01

The resistance to late blight is either qualitative or quantitative in nature. Quantitative resistance is durable, but challenging due to polygenic inheritance. In the present study, the diploid potato genotypes resistant and susceptible to late blight, were profiled for metabolites. Tissue specific metabolite analysis of benzylisoquinoline alkaloids (BIAs) in response to pathogen infection revealed increased accumulation of morphinone, codeine-6-glucuronide and morphine-3-glucuronides. These BIAs are antimicrobial compounds and possibly involved in cell wall reinforcement, especially through cross-linking cell wall pectins. Quantitative reverse transcription-PCR studies revealed higher expressions of TyDC, NCS, COR-2 and StWRKY8 transcription factor genes, in resistant genotypes than in susceptible genotype, following pathogen inoculation. A luciferase transient expression assay confirmed the binding of the StWRKY8 TF to promoters of downstream genes, elucidating a direct regulatory role on BIAs biosynthetic genes. Sequence analysis of StWRKY8 in potato genotypes revealed polymorphism in the WRKY DNA binding domain in the susceptible genotype, which is important for the regulatory function of this gene. A complementation assay of StWRKY8 in Arabidopsis wrky33 mutant background was associated with decreased fungal biomass. In conclusion, StWRKY8 regulates the biosynthesis of BIAs that are both antimicrobial and reinforce cell walls to contain the pathogen to initial infection. Copyright © 2017 Elsevier B.V. All rights reserved.

Aggressiveness Changes in Populations of Didymella pinodes over Winter and Spring Pea Cropping Seasons

PubMed Central

Laloi, G.; Montarry, J.; Guibert, M.; Andrivon, D.; Michot, D.

2016-01-01

ABSTRACT Ascochyta blight, caused by the necrotrophic ascomycete Didymella pinodes, is responsible for severe losses in winter and spring pea crops. Despite different climatic conditions, epidemics on winter and spring crops are due to a single population of D. pinodes, suggesting gene flow either between the two crops or from reservoir sources during the cropping season. This should lead to similar pathogenicity characteristics in isolates sampled from the two crops. However, these hypotheses have never been formally tested. We therefore sampled a total of 520 D. pinodes strains throughout a growing season from winter and spring pea plots (WP and SP, respectively) and from winter and spring trap plants (TWP and TSP). Amplified fragment length polymorphism (AFLP) markers revealed high genetic diversity within subpopulations, whereas pathogenicity tests showed that mean aggressiveness increases over the course of an epidemic. These results support the idea that alloinoculum contributes to the carryover of epidemics between winter and spring crops and that the most aggressive isolates are selected as an epidemic progresses. IMPORTANCE Ascochyta blight, caused by Didymella pinodes, is responsible for severe losses in pea crops. While previous studies have shown that ascochyta blight epidemics on winter and spring crops are due to a single population of D. pinodes, suggesting that isolates from the two crops present similar pathogenicity characteristics, that hypothesis have never been tested. Genetic analysis of subpopulations sampled throughout a growing season from winter and spring pea plots revealed high genetic diversity within subpopulations, whereas pathogenicity tests showed that mean aggressiveness increases over the course of an epidemic. PMID:27208102

Characterization of Ascochyta rabiei for population structure, mating type and pathogenic variability from Pakistan and United States

USDA-ARS?s Scientific Manuscript database

Chickpea production is greatly hampered by blight causing fungal pathogen Ascochyta rabiei (AR) in chickpea growing regions of the world. Genetic variability and mating type frequency of thirty-two AR isolates from six geographical regions of Pakistan were compared with a US-AR population. Pakistani...

Analysis of apple (Malus) responses to bacterial pathogens using an oligo microarray

USDA-ARS?s Scientific Manuscript database

Fire blight is a devastating disease of apple (Malus x domestica) caused by the bacterial pathogen Erwinia amylovora (Ea). When infiltrated into host leaves, Ea induces reactions similar to a hypersensitive response (HR). Type III (T3SS) associated effectors, especially DspA/E, are suspected to ha...

Complete genome of the cotton bacteria blight pathogen Xanthomonas citri pv. malvacearum strain MSCT

USDA-ARS?s Scientific Manuscript database

Xanthomonas citri pv. malvacearum (Xcm) is a major pathogen of Gossypium hirsutum. In this study we report the complete genome of the Xcm strain MSCT assembled from long read DNA sequencing technology. The MSCT genome is the first Xcm genome that has complete coding regions for Xcm transcriptional a...

Applying RNA Sequencing to investigate pathogenic mechanisms of Ascochyta rabiei

USDA-ARS?s Scientific Manuscript database

Ascochyta rabiei causes Ascochyta blight of chickpea. To study the pathogenic mechanisms of A. rabiei, total mRNAs were isolated from isolates AR19 of pathotype I and AR628 of pathotype II of A. rabiei, and also from diseased tissues of chickpea ‘Spanish White’ inoculated with these two isolates at ...

Comparative population genomics of fusarium graminearum reveals adaptive divergence among cereal head blight pathogens

USDA-ARS?s Scientific Manuscript database

During the last decade, a combination of molecular surveillance and population genetic analyses have significantly altered our understanding of Fusarium graminearum, the major FHB pathogen in North America. In addition to the native NA1 population (largely 15ADON toxin type) and the invasive NA2 pop...

Code-assisted discovery of TAL effector targets in bacterial leaf streak of rice reveals contrast with bacterial blight and a novel susceptibility gene

USDA-ARS?s Scientific Manuscript database

Transcription activator-like (TAL) effectors found in Xanthomonas spp. promote bacterial growth and plant susceptibility by binding specific DNA sequences or, effector-binding elements (EBEs), and inducing host gene expression. In this study, we have found substantially different transcriptional pro...

Phylogenetic prediction of Alternaria leaf blight resistance in wild and cultivated species of carrots (Daucus, Apiaceae)

USDA-ARS?s Scientific Manuscript database

Plant scientists make inferences and predictions from phylogenetic trees to solve scientific problems. Crop losses due to disease damage is an important problem that many plant breeders would like to solve, so the ability to predict traits like disease resistance from phylogenetic trees derived from...

Ornamental and Turf Pest Control. Bulletin 764.

ERIC Educational Resources Information Center

Bowyer, Timothy H.; And Others

This manual gives descriptions of and methods for control of diseases and insect pests of ornamental plants, weeds, and diseases and insect pests of turf plants. Included are diseases caused by fungi such as cankers, leaf galls, and rust; diseases caused by bacteria such as bacterial blight and crown gall; and diseases caused by nematodes and…

Yield effecgs of two southern leaf blight resistance loci in maize hybrids

USDA-ARS?s Scientific Manuscript database

Plants need to balance resources between yield and defense. This phenomenon has rarely been investigated in the context of naturally-occurring quantitative resistance alleles in an agricultural production environment. B73-3B and B73-6A are two near-isogenic lines (NILs) in the background of the mai...

Automated Identification of Northern Leaf Blight-Infected Maize Plants from Field Imagery Using Deep Learning.

PubMed

DeChant, Chad; Wiesner-Hanks, Tyr; Chen, Siyuan; Stewart, Ethan L; Yosinski, Jason; Gore, Michael A; Nelson, Rebecca J; Lipson, Hod

2017-11-01

Northern leaf blight (NLB) can cause severe yield loss in maize; however, scouting large areas to accurately diagnose the disease is time consuming and difficult. We demonstrate a system capable of automatically identifying NLB lesions in field-acquired images of maize plants with high reliability. This approach uses a computational pipeline of convolutional neural networks (CNNs) that addresses the challenges of limited data and the myriad irregularities that appear in images of field-grown plants. Several CNNs were trained to classify small regions of images as containing NLB lesions or not; their predictions were combined into separate heat maps, then fed into a final CNN trained to classify the entire image as containing diseased plants or not. The system achieved 96.7% accuracy on test set images not used in training. We suggest that such systems mounted on aerial- or ground-based vehicles can help in automated high-throughput plant phenotyping, precision breeding for disease resistance, and reduced pesticide use through targeted application across a variety of plant and disease categories.

Characterization and fine mapping of a light-dependent leaf lesion mimic mutant 1 in rice.

PubMed

Wang, Jing; Ye, Bangquan; Yin, Junjie; Yuan, Can; Zhou, Xiaogang; Li, Weitao; He, Min; Wang, Jichun; Chen, Weilan; Qin, Peng; Ma, Bintian; Wang, Yuping; Li, Shigui; Chen, Xuewei

2015-12-01

Plants that spontaneously produce lesion mimics or spots, without any signs of obvious adversity, such as pesticide and mechanical damage, or pathogen infection, are so-called lesion mimic mutants (lmms). In rice, many lmms exhibit enhanced resistance to pathogens, which provides a unique opportunity to uncover the molecular mechanism underlying lmms. We isolated a rice light-dependent leaf lesion mimic mutant 1 (llm1). Lesion spots appeared in the leaves of the llm1 mutant at the tillering stage. Furthermore, the mutant llm1 had similar agronomic traits to wild type rice. Trypan blue and diamiobenzidine staining analyses revealed that the lesion spot formation on the llm1 mutant was due to programmed cell death and reactive oxygen species. The chloroplasts were severely damaged in the llm1 mutant, suggesting that chloroplast damage was associated with the formation of lesion spots in llm1. More importantly, llm1 exhibited enhanced resistance to bacterial blight pathogens within increased expression of pathogenesis related genes (PRs). Using a map-based cloning approach, we delimited the LLM1 locus to a 121-kb interval between two simple sequence repeat markers, RM17470 and RM17473, on chromosome 4. We sequenced the candidate genes on the interval and found that a base mutation had substituted adenine phosphate for thymine in the last exon of LOC_Os04g52130, which led to an amino acid change (Asp(388) to Val) in the llm1 mutant. Our investigation showed that the putative coproporphyrinogen III oxidase (CPOX) encoded by LOC_Os04g52130 was produced by LLM1 and that amino acid Asp(388) was essential for CPOX function. Our study provides the basis for further investigations into the mechanism underlying lesion mimic initiation associated with LLM1. Copyright © 2015 Elsevier Masson SAS. All rights reserved.

Evidence that the Ceratobasidium-like white-thread blight and black rot fungal pathogens from persimmon and tea crops in the Brazilian Atlantic Forest agroecosystem are two distinct phylospecies

PubMed Central

Ceresini, Paulo C.; Costa-Souza, Elaine; Zala, Marcello; Furtado, Edson L.; Souza, Nilton L.

2012-01-01

The white-thread blight and black rot (WTBR) caused by basidiomycetous fungi of the genus Ceratobasidium is emerging as an important plant disease in Brazil, particularly for crop species in the Ericales such as persimmon (Diospyros kaki) and tea (Camellia sinensis). However, the species identity of the fungal pathogen associated with either of these hosts is still unclear. In this work, we used sequence variation in the internal transcribed spacer regions, including the 5.8S coding region of rDNA (ITS-5.8S rDNA), to determine the phylogenetic placement of the local white-thread-blight-associated populations of Ceratobasidium sp. from persimmon and tea, in relation to Ceratobasidium species already described world-wide. The two sister populations of Ceratobasidium sp. from persimmon and tea in the Brazilian Atlantic Forest agroecosystem most likely represent distinct species within Ceratobasidium and are also distinct from C. noxium, the etiological agent of the first description of white-thread blight disease that was reported on coffee in India. The intraspecific variation for the two Ceratobasidium sp. populations was also analyzed using three mitochondrial genes (ATP6, nad1 and nad2). As reported for other fungi, variation in nuclear and mitochondrial DNA was incongruent. Despite distinct variability in the ITS-rDNA region these two populations shared similar mitochondrial DNA haplotypes. PMID:22888299

Efficacy of different fungicides against Rhizoctonia brown patch and Pythium blight on turfgrass in Italy.

PubMed

Mocioni, M; Titone, P; Garibaldi, A; Gullino, M L

2003-01-01

Brown patch, incited by Rhizoctonia solani Kuhn, and Pythium blight, caused by Pythium spp. are two of the diseases most frequently observed on turfgrass in high maintenance stands, as on golf courses. In such conditions the control strategies, based on chemicals, are particularly difficult due to the scarcity of fungicides registered for turf in Italy. The results obtained in experimental trials carried out to evaluate the efficacy of chemical and biological products against brown patch and Pythium blight are reported. On mature turfgrass, maintained under fairway conditions, azoxystrobin, and trifoxystrobin, not yet registered on turf, were very effective against brown patch. Tebuconazole, applied in three different formulations, was very effective against R. solani, while Trichoderma spp. and azadiractine did not control the pathogen. In greenhouse conditions on Agrostis stolonifera, in the presence of severe disease incidence, due to artificial inoculation, benalaxyl-M satisfactorily controlled Pythium blight; Trichoderma spp. as well as a commercial formulation of T. harzianum, applied one week before the inoculation, were not effective. Among the fungicides not yet registered for use on turfgrass in Italy, metalaxyl-M + mancozeb was effective against Pythium blight.

Actinomycetes from Eucalyptus and their biological activities for controlling Eucalyptus leaf and shoot blight.

PubMed

Himaman, Winanda; Thamchaipenet, Arinthip; Pathom-Aree, Wasu; Duangmal, Kannika

2016-01-01

In Thailand, Eucalyptus plantations rapidly expand across the country. Leaf and shoot blight caused by Cryptosporiopsis eucalypti, Cylindrocladium sp. and Teratosphaeria destructans is a serious disease in Eucalyptus plantations. In this study, a total of 477 actinomycete strains were successfully isolated from roots and rhizosphere soil of Eucalyptus. Four hundred and thirty nine isolates were classified as streptomycetes and 38 isolates were non-streptomycetes. Among these isolates, 272 (57.0%), 118 (24.7%) and 241 (50.5%) isolates were antagonistic to Cryptosporiopsis eucalypti, Cylindrocladium sp. and Teratosphaeria destructans, respectively. All isolates were tested for their abilities to produce siderophores, indole acetic acid (IAA) and solubilise phosphate. Most isolates (464, 97.3%) produced siderophores. The majority of isolates (345, 72.3%) solubilised phosphate. In addition, almost half of these isolates (237, 49.7%) produced indole acetic acid. Strain EUSKR2S82 which showed the strongest inhibitory effect against all tested fungi with plant growth promoting ability was selected to test with Eucalyptus. This strain could colonize plant roots and increase Eucalyptus roots length. In a detached leaves bioassay, the disease severity of EUSKR2S82-inoculated Eucalyptus leaves was only 30% compared to 95% in the control treatment. The 16S rRNA gene sequence analysis revealed that the strain EUSKR2S82 was related to Streptomyces ramulosus NRRL-B 2714(T) (99.44% similarity). Identification of non-streptomycete isolates using 16S rRNA gene sequences classified them into 9 genera: Actinoallomurus, Actinomadura, Amycolatopsis, Cryptosporangium, Microbispora, Micromonospora, Nocardia, Nonomuraea and Pseudonocardia. It is evident that Eucalyptus tree harbored several genera of actinomycetes. The selected isolate, EUSKR2S82 showed potential as a candidate for biocontrol agent of leaf and shoot blight of Eucalyptus and to promote growth. Copyright © 2016 Elsevier GmbH. All rights reserved.

Management of blight of bell pepper (Capsicum annuum var. grossum) caused by Drechslera bicolor.

PubMed

Jadon, Kuldeep Singh; Shah, Rakesh; Gour, Hari Narayan; Sharma, Pankaj

Sweet or bell pepper is a member of the Solanaceae family and is regarded as one of the most popular and nutritious vegetable. Blight, in the form of leaf and fruit blight, has been observed to infect bell pepper crops cultivated at the horticulture farm in Rajasthan College of Agriculture, Udaipur, India. Based on disease severity, we attempted to curb this newly emerged problem using different fungicides, plant extracts, bio-control agents, and commercial botanicals against the fungus in laboratory and pot experiments. Bio-control agent Trichoderma viride and plant growth promoting Rhizobacteria (PGPR) isolate Neist-2 were found to be quite effective against bell pepper blight. All evaluated fungicides, botanicals, commercial botanicals, and bio-control agents in vitro were further studied as seed dressers and two foliar sprays at ten days interval in pot experiments. The combinations of Vitavax, PGPR isolate Neist-2, and Mehandi extract were found to be very effective against bell pepper blight followed by Vitavax, T. viride, and Mehandi extract used individually. All treatments in the pot experiments were found to significantly reduce seedling mortality and enhance plant biomass of bell pepper. Thus, these experimental findings suggest that a better integrated management of bell pepper blight could be achieved by conducting field trials in major bell pepper- and chilli-cultivated areas of the state. Besides fungicides, different botanicals and commercial botanicals also seem to be promising treatment options. Therefore, the outcome of the present study provides an alternate option of fungicide use in minimizing loss caused by Drechslera bicolor. Copyright © 2016 Sociedade Brasileira de Microbiologia. Published by Elsevier Editora Ltda. All rights reserved.

Potato NPH3/RPT2-Like Protein StNRL1, Targeted by a Phytophthora infestans RXLR Effector, Is a Susceptibility Factor.

PubMed

Yang, Lina; McLellan, Hazel; Naqvi, Shaista; He, Qin; Boevink, Petra C; Armstrong, Miles; Giuliani, Licida M; Zhang, Wei; Tian, Zhendong; Zhan, Jiasui; Gilroy, Eleanor M; Birch, Paul R J

2016-05-01

Plant pathogens deliver effectors to manipulate host processes. We know little about how fungal and oomycete effectors target host proteins to promote susceptibility, yet such knowledge is vital to understand crop disease. We show that either transient expression in Nicotiana benthamiana, or stable transgenic expression in potato (Solanum tuberosum), of the Phytophthora infestans RXLR effector Pi02860 enhances leaf colonization by the pathogen. Expression of Pi02860 also attenuates cell death triggered by the P. infestans microbe-associated molecular pattern INF1, indicating that the effector suppresses pattern-triggered immunity. However, the effector does not attenuate cell death triggered by Cf4/Avr4 coexpression, showing that it does not suppress all cell death activated by cell surface receptors. Pi02860 interacts in yeast two-hybrid assays with potato NPH3/RPT2-LIKE1 (NRL1), a predicted CULLIN3-associated ubiquitin E3 ligase. Interaction of Pi02860 in planta was confirmed by coimmunoprecipitation and bimolecular fluorescence complementation assays. Virus-induced gene silencing of NRL1 in N. benthamiana resulted in reduced P. infestans colonization and accelerated INF1-mediated cell death, indicating that this host protein acts as a negative regulator of immunity. Moreover, whereas NRL1 virus-induced gene silencing had no effect on the ability of the P. infestans effector Avr3a to suppress INF1-mediated cell death, such suppression by Pi02860 was significantly attenuated, indicating that this activity of Pi02860 is mediated by NRL1. Transient overexpression of NRL1 resulted in the suppression of INF1-mediated cell death and enhanced P. infestans leaf colonization, demonstrating that NRL1 acts as a susceptibility factor to promote late blight disease. © 2016 American Society of Plant Biologists. All Rights Reserved.

Control of fire blight (Erwinia amylovora) on apple trees with trunk-injected plant resistance inducers and antibiotics and assessment of induction of pathogenesis-related protein genes

PubMed Central

Aćimović, Srđan G.; Zeng, Quan; McGhee, Gayle C.; Sundin, George W.; Wise, John C.

2015-01-01

Management of fire blight is complicated by limitations on use of antibiotics in agriculture, antibiotic resistance development, and limited efficacy of alternative control agents. Even though successful in control, preventive antibiotic sprays also affect non-target bacteria, aiding the selection for resistance which could ultimately be transferred to the pathogen Erwinia amylovora. Trunk injection is a target-precise pesticide delivery method that utilizes tree xylem to distribute injected compounds. Trunk injection could decrease antibiotic usage in the open environment and increase the effectiveness of compounds in fire blight control. In field experiments, after 1–2 apple tree injections of either streptomycin, potassium phosphites (PH), or acibenzolar-S-methyl (ASM), significant reduction of blossom and shoot blight symptoms was observed compared to water injected control trees. Overall disease suppression with streptomycin was lower than typically observed following spray applications to flowers. Trunk injection of oxytetracycline resulted in excellent control of shoot blight severity, suggesting that injection is a superior delivery method for this antibiotic. Injection of both ASM and PH resulted in the significant induction of PR-1, PR-2, and PR-8 protein genes in apple leaves indicating induction of systemic acquired resistance (SAR) under field conditions. The time separating SAR induction and fire blight symptom suppression indicated that various defensive compounds within the SAR response were synthesized and accumulated in the canopy. ASM and PH suppressed fire blight even after cessation of induced gene expression. With the development of injectable formulations and optimization of doses and injection schedules, the injection of protective compounds could serve as an effective option for fire blight control. PMID:25717330

Molecular Cytogenetic Characterization of two Triticum-Secale-Thinopyrum Trigeneric Hybrids Exhibiting Superior Resistance to Fusarium Head Blight, Leaf Rust, and Stem Rust Race Ug99.

PubMed

Dai, Yi; Duan, Yamei; Liu, Huiping; Chi, Dawn; Cao, Wenguang; Xue, Allen; Gao, Yong; Fedak, George; Chen, Jianmin

2017-01-01

Fusarium head blight (FHB), leaf rust, and stem rust are the most destructive fungal diseases in current world wheat production. The diploid wheatgrass, Thinopyrum elongatum (Host) Dewey (2 n = 2 x = 14, EE) is an excellent source of disease resistance genes. Two new Triticum-Secale-Thinopyrum trigeneric hybrids were derived from a cross between a hexaploid triticale (X Triticosecale Wittmack, 2 n = 6 x = 42, AABBRR) and a hexaploid Triticum trititrigia (2 n = 6 x = 42, AABBEE), were produced and analyzed using genomic in situ hybridization and molecular markers. The results indicated that line RE21 contained 14 A-chromosomes, 14 B-chromosomes, three pairs of R-chromosomes (4R, 6R, and 7R), and four pairs of E-chromosomes (1E, 2E, 3E, and 5E) for a total chromosome number of 2 n = 42. Line RE62 contained 14 A-chromosomes, 14 B-chromosomes, six pairs of R-chromosomes, and one pair of translocation chromosomes between chromosome 5R and 5E, for a total chromosome number of 2 n = 42. At the seedling and adult growth stages under greenhouse conditions, line RE21 showed high levels of resistance to FHB, leaf rust, and stem rust race Ug99, and line RE62 was highly resistant to leaf rust and stem rust race Ug99. These two lines (RE21 and RE62) display superior disease resistance characteristics and have the potential to be utilized as valuable germplasm sources for future wheat improvement.

Population subdivision of Fusarium graminearum from barley and wheat in the upper Midwestern United States at the turn of the century

USDA-ARS?s Scientific Manuscript database

Fusarium graminearum, the causal agent of Fusarium head blight (FHB) in wheat and barley, is one of the most economically destructive pathogens of these grains worldwide. Recent population genetic studies of the pathogen obtained from wheat in North America supported population subdivision in part c...

Demonstrating the benefits of phytosanitary regulations: the case of ISPM 15

Treesearch

Eckehard G. Brockerhoff; Juliann E. Aukema; Joseph F. Cavey; Lynn J. Garrett; Robert A. Haack; Mark Kimberley; Andrew M. Liebhold; Frank L. Lowenstein; Carissa Marasas; Amelia Nuding; Lars Olson; Christa Speekmann; Michael Springborn; Christina Vieglais; James Turner

2011-01-01

Invasions of non-indigenous insects and pathogens threaten trees and forest ecosystems worldwide. For example, the arrival and spread of the pathogens causing chestnut blight and Dutch elm disease, along with the bark beetles vectoring the latter, had dramatic effects on North American forests. Despite our improved awareness of the risks associated with biological...

Corynespora cassiicola f. sp. schinii, a potential biocontrol agent for the weed Schinus terebinthifolius in the United States

USDA-ARS?s Scientific Manuscript database

An isolate of Corynespora cassiicola was found in Brazil (state of Espírito Santo) causing a severe leaf spot and foliage blight on Schinus terebinthifolius (Anacardiaceae, Brazilian peppertree or ‘aroeira’) which is a major environmental weed in many tropical and sub-tropical areas of the globe, in...

Synthesis and Biological Activity of Substituted Urea and Thiourea Derivatives Containing 1,2,4-Triazole Moieties

DTIC Science & Technology

2013-03-19

vine grape production in the United States of America and Europe, while P. obscurans causes Phomopsis leaf blight and fruit rot of strawberry ... strawberry fruit rot diseases in Louisiana and Mississippi. Crop Protect. 2007, 26, 1449–1458. 25. Denny, W.A.; Cain, B.F.; Atwell, G.J.; Hansch, C

Management of sheath blight and narrow brown leaf spot with biocontrol agents in organic rice, 2010

USDA-ARS?s Scientific Manuscript database

The experiment was established in a field of League-type soil (3% sand, 32% silt, and 64% clay) under organic management for many years at the Texas A&M University System's Agrilife Research and Extension Center, Beaumont. Plots consisted of seven 18-ft rows, and spaced 7 inches between rows. There ...

Do transgenesis and marker-assisted backcross breeding produce substantially equivalent plants? A comparative study of transgenic and backcross rice carrying bacterial blight resistant gene Xa21.

PubMed

Gao, Lifen; Cao, Yinghao; Xia, Zhihui; Jiang, Guanghuai; Liu, Guozhen; Zhang, Weixiong; Zhai, Wenxue

2013-10-29

The potential impact of genetically modified (GM) plants on human health has attracted much attention worldwide, and the issue remains controversial. This is in sharp contrast to the broad acceptance of plants produced by breeding through Marker Assisted Backcrossing (MAB). Focusing on transcriptome variation and perturbation to signaling pathways, we assessed the molecular and biological aspects of substantial equivalence, a general principle for food safety endorsed by the Food and Agricultural Organization and the World Health Organization, between a transgenic crop and a plant from MAB breeding. We compared a transgenic rice line (DXT) and a MAB rice line (DXB), both of which contain the gene Xa21 providing resistance to bacterial leaf blight. By using Next-Generation sequencing data of DXT, DXB and their parental line (D62B), we compared the transcriptome variation of DXT and DXB. Remarkably, DXT had 43% fewer differentially expressed genes (DEGs) than DXB. The genes exclusively expressed in DXT and in DXB have pathogen and stress defense functions. Functional categories of DEGs in DXT were comparable to that in DXB, and seven of the eleven pathways significantly affected by transgenesis were also perturbed by MAB breeding. These results indicated that the transgenic rice and rice from MAB breeding are substantial equivalent at the transcriptome level, and paved a way for further study of transgenic rice, e.g., understanding the chemical and nutritional properties of the DEGs identified in the current study.

Do transgenesis and marker-assisted backcross breeding produce substantially equivalent plants? - A comparative study of transgenic and backcross rice carrying bacterial blight resistant gene Xa21

PubMed Central

2013-01-01

Background The potential impact of genetically modified (GM) plants on human health has attracted much attention worldwide, and the issue remains controversial. This is in sharp contrast to the broad acceptance of plants produced by breeding through Marker Assisted Backcrossing (MAB). Results Focusing on transcriptome variation and perturbation to signaling pathways, we assessed the molecular and biological aspects of substantial equivalence, a general principle for food safety endorsed by the Food and Agricultural Organization and the World Health Organization, between a transgenic crop and a plant from MAB breeding. We compared a transgenic rice line (DXT) and a MAB rice line (DXB), both of which contain the gene Xa21 providing resistance to bacterial leaf blight. By using Next-Generation sequencing data of DXT, DXB and their parental line (D62B), we compared the transcriptome variation of DXT and DXB. Remarkably, DXT had 43% fewer differentially expressed genes (DEGs) than DXB. The genes exclusively expressed in DXT and in DXB have pathogen and stress defense functions. Functional categories of DEGs in DXT were comparable to that in DXB, and seven of the eleven pathways significantly affected by transgenesis were also perturbed by MAB breeding. Conclusions These results indicated that the transgenic rice and rice from MAB breeding are substantial equivalent at the transcriptome level, and paved a way for further study of transgenic rice, e.g., understanding the chemical and nutritional properties of the DEGs identified in the current study. PMID:24165682

Aggressiveness Changes in Populations of Didymella pinodes over Winter and Spring Pea Cropping Seasons.

PubMed

Laloi, G; Montarry, J; Guibert, M; Andrivon, D; Michot, D; Le May, C

2016-07-15

Ascochyta blight, caused by the necrotrophic ascomycete Didymella pinodes, is responsible for severe losses in winter and spring pea crops. Despite different climatic conditions, epidemics on winter and spring crops are due to a single population of D. pinodes, suggesting gene flow either between the two crops or from reservoir sources during the cropping season. This should lead to similar pathogenicity characteristics in isolates sampled from the two crops. However, these hypotheses have never been formally tested. We therefore sampled a total of 520 D. pinodes strains throughout a growing season from winter and spring pea plots (WP and SP, respectively) and from winter and spring trap plants (TWP and TSP). Amplified fragment length polymorphism (AFLP) markers revealed high genetic diversity within subpopulations, whereas pathogenicity tests showed that mean aggressiveness increases over the course of an epidemic. These results support the idea that alloinoculum contributes to the carryover of epidemics between winter and spring crops and that the most aggressive isolates are selected as an epidemic progresses. Ascochyta blight, caused by Didymella pinodes, is responsible for severe losses in pea crops. While previous studies have shown that ascochyta blight epidemics on winter and spring crops are due to a single population of D. pinodes, suggesting that isolates from the two crops present similar pathogenicity characteristics, that hypothesis have never been tested. Genetic analysis of subpopulations sampled throughout a growing season from winter and spring pea plots revealed high genetic diversity within subpopulations, whereas pathogenicity tests showed that mean aggressiveness increases over the course of an epidemic. Copyright © 2016, American Society for Microbiology. All Rights Reserved.

Alterations in Kernel Proteome after Infection with Fusarium culmorum in Two Triticale Cultivars with Contrasting Resistance to Fusarium Head Blight

PubMed Central

Perlikowski, Dawid; Wiśniewska, Halina; Kaczmarek, Joanna; Góral, Tomasz; Ochodzki, Piotr; Kwiatek, Michał; Majka, Maciej; Augustyniak, Adam; Kosmala, Arkadiusz

2016-01-01

Highlight: The level of pathogen alpha-amylase and plant beta-amylase activities could be components of plant-pathogen interaction associated with the resistance of triticale to Fusarium head blight. Triticale was used here as a model to recognize new components of molecular mechanism of resistance to Fusarium head blight (FHB) in cereals. Fusarium-damaged kernels (FDK) of two lines distinct in levels of resistance to FHB were applied into a proteome profiling using two-dimensional gel electrophoresis (2-DE) to create protein maps and mass spectrometry (MS) to identify the proteins differentially accumulated between the analyzed lines. This proteomic research was supported by a measurement of alpha- and beta-amylase activities, mycotoxin content, and fungal biomass in the analyzed kernels. The 2-DE analysis indicated a total of 23 spots with clear differences in a protein content between the more resistant and more susceptible triticale lines after infection with Fusarium culmorum. A majority of the proteins were involved in a cell carbohydrate metabolism, stressing the importance of this protein group in a plant response to Fusarium infection. The increased accumulation levels of different isoforms of plant beta-amylase were observed for a more susceptible triticale line after inoculation but these were not supported by a total level of beta-amylase activity, showing the highest value in the control conditions. The more resistant line was characterized by a higher abundance of alpha-amylase inhibitor CM2 subunit and simultaneously a lower activity of alpha-amylase after inoculation. We suggest that the level of pathogen alpha-amylase and plant beta-amylase activities could be components of plant-pathogen interaction associated with the resistance of triticale to FHB. PMID:27582751

Genotype-Dependent Interaction of Lentil Lines with Ascochyta lentis

PubMed Central

Sari, Ehsan; Bhadauria, Vijai; Vandenberg, Albert; Banniza, Sabine

2017-01-01

Ascochyta blight of lentil is a prevalent disease in many lentil producing regions and can cause major yield and grain quality losses. The most environmentally acceptable and economically profitable method of control is to develop varieties with high levels of durable resistance. Genetic studies to date suggest that ascochyta blight resistance genes (R-gene) in lentil lines CDC Robin, ILL 7537, 964a-46, and ILL 1704 are non-allelic. To understand how different R-genes manifest resistance in these genotypes and an accession of Lens ervoides, L-01-827A, with high level of resistance to ascochyta blight, cellular and molecular defense responses were compared after inoculation with the causal pathogen Ascochyta lentis. Pathogenicity testing of the resistant lines to A. lentis inoculation revealed significantly lower disease severity on CDC Robin and ILL 7537 compared to ILL 1704 and 964a-46, and no symptoms of disease were observed on L-01-827A. Histological examinations indicated that cell death triggered by the pathogen might be disrupted as a mechanism of resistance in CDC Robin. In contrast, limiting colonization of epidermal cells by A. lentis is a suggested mechanism of resistance in 964a-46. A time-series comparison of the expressions of hallmark genes in salicylic acid (SA) and jasmonic acid (JA) signal transduction pathways between CDC Robin and 964a-46 was conducted. These partially resistant genotypes differed in the timing and the magnitude of SA and JA signaling pathway activation. The SA signaling pathway was only triggered in 964a-46, whereas the JA pathway was triggered in both partially resistant genotypes CDC Robin and 964a-46. The expression of JA-associated genes was lower in 964a-46 than CDC Robin. These observations corroborate the existence of diverse ascochyta blight resistance mechanisms in lentil genotypes carrying different R-genes. PMID:28539932

Protein profiling in potato (Solanum tuberosum L.) leaf tissues by differential centrifugation.

PubMed

Lim, Sanghyun; Chisholm, Kenneth; Coffin, Robert H; Peters, Rick D; Al-Mughrabi, Khalil I; Wang-Pruski, Gefu; Pinto, Devanand M

2012-04-06

Foliar diseases, such as late blight, result in serious threats to potato production. As such, potato leaf tissue becomes an important substrate to study biological processes, such as plant defense responses to infection. Nonetheless, the potato leaf proteome remains poorly characterized. Here, we report protein profiling of potato leaf tissues using a modified differential centrifugation approach to separate the leaf tissues into cell wall and cytoplasmic fractions. This method helps to increase the number of identified proteins, including targeted putative cell wall proteins. The method allowed for the identification of 1484 nonredundant potato leaf proteins, of which 364 and 447 were reproducibly identified proteins in the cell wall and cytoplasmic fractions, respectively. Reproducibly identified proteins corresponded to over 70% of proteins identified in each replicate. A diverse range of proteins was identified based on their theoretical pI values, molecular masses, functional classification, and biological processes. Such a protein extraction method is effective for the establishment of a highly qualified proteome profile.

Xanthomonas TAL effectors hijack host basal transcription factor IIA α and γ subunits for invasion.

PubMed

Ma, Ling; Wang, Qiang; Yuan, Meng; Zou, Tingting; Yin, Ping; Wang, Shiping

2018-02-05

The Xanthomonas genus includes Gram-negative plant-pathogenic bacteria, which infect a broad range of crops and wild plant species, cause symptoms with leaf blights, streaks, spots, stripes, necrosis, wilt, cankers and gummosis on leaves, stems and fruits in a wide variety of plants via injecting their effector proteins into the host cell during infection. Among these virulent effectors, transcription activator-like effectors (TALEs) interact with the γ subunit of host transcription factor IIA (TFIIAγ) to activate the transcription of host disease susceptibility genes. Functional TFIIA is a ternary complex comprising α, β and γ subunits. However, whether TALEs recruit TFIIAα, TFIIAβ, or both remains unknown. The underlying molecular mechanisms by which TALEs mediate host susceptibility gene activation require full elucidation. Here, we show that TALEs interact with the α+γ binary subcomplex but not the α+β+γ ternary complex of rice TFIIA (holo-OsTFIIA). The transcription factor binding (TFB) regions of TALEs, which are highly conserved in Xanthomonas species, have a dominant role in these interactions. Furthermore, the interaction between TALEs and the α+γ complex exhibits robust DNA binding activity in vitro. These results collectively demonstrate that TALE-carrying pathogens hijack the host basal transcription factors TFIIAα and TFIIAγ, but not TFIIAβ, to enhance host susceptibility during pathogen infection. The uncovered mechanism widens new insights on host-microbe interaction and provide an applicable strategy to breed high-resistance crop varieties. Copyright © 2018 Elsevier Inc. All rights reserved.

Determinants of Virulence and In Vitro Development Colocalize on a Genetic Map of Setosphaeria turcica.

PubMed

Mideros, Santiago X; Chung, Chia-Lin; Wiesner-Hanks, Tyr; Poland, Jesse A; Wu, Dongliang; Fialko, Ariel A; Turgeon, B Gillian; Nelson, Rebecca J

2018-02-01

Generating effective and stable strategies for resistance breeding requires an understanding of the genetics of host-pathogen interactions and the implications for pathogen dynamics and evolution. Setosphaeria turcica causes northern leaf blight (NLB), an important disease of maize for which major resistance genes have been deployed. Little is known about the evolutionary dynamics of avirulence (AVR) genes in S. turcica. To test the hypothesis that there is a genetic association between avirulence and in vitro development traits, we (i) created a genetic map of S. turcica, (ii) located candidate AVRHt1 and AVRHt2 regions, and (iii) identified genetic regions associated with several in vitro development traits. A cross was generated between a race 1 and a race 23N strain, and 221 progeny were isolated. Genotyping by sequencing was used to score 2,078 single-nucleotide polymorphism markers. A genetic map spanning 1,981 centimorgans was constructed, consisting of 21 linkage groups. Genetic mapping extended prior evidence for the location and identity of the AVRHt1 gene and identified a region of interest for AVRHt2. The genetic location of AVRHt2 colocalized with loci influencing radial growth and mycelial abundance. Our data suggest a trade-off between virulence on Ht1 and Ht2 and the pathogen's vegetative growth rate. In addition, in-depth analysis of the genotypic data suggests the presence of significant duplication in the genome of S. turcica.

LAMP detection assays for boxwood blight pathogens: A comparative genomics approach

DOE Office of Scientific and Technical Information (OSTI.GOV)

Malapi-Wight, Martha; Demers, Jill E.; Veltri, Daniel

Rapid and accurate molecular diagnostic tools are critical to efforts to minimize the impact and spread of emergent pathogens. The identification of diagnostic markers for novel pathogens presents several challenges, especially in the absence of information about population diversity and where genetic resources are limited. The objective of this study was to use comparative genomics datasets to find unique target regions suitable for the diagnosis of two fungal species causing a newly emergent blight disease of boxwood. Candidate marker regions for loop-mediated isothermal amplification (LAMP) assays were identified from draft genomes of Calonectria henricotiae and C. pseudonaviculata, as well asmore » three related species not associated with this disease. To increase the probability of identifying unique targets, we used three approaches to mine genome datasets, based on (i) unique regions, (ii) polymorphisms, and (iii) presence/absence of regions across datasets. From a pool of candidate markers, we demonstrate LAMP assay specificity by testing related fungal species, common boxwood pathogens, and environmental samples containing 445 diverse fungal taxa. In conclusion, this comparative-genomics-based approach to the development of LAMP diagnostic assays is the first of its kind for fungi and could be easily applied to diagnostic marker development for other newly emergent plant pathogens.« less

LAMP detection assays for boxwood blight pathogens: A comparative genomics approach

DOE PAGES

Malapi-Wight, Martha; Demers, Jill E.; Veltri, Daniel; ...

2016-05-20

Rapid and accurate molecular diagnostic tools are critical to efforts to minimize the impact and spread of emergent pathogens. The identification of diagnostic markers for novel pathogens presents several challenges, especially in the absence of information about population diversity and where genetic resources are limited. The objective of this study was to use comparative genomics datasets to find unique target regions suitable for the diagnosis of two fungal species causing a newly emergent blight disease of boxwood. Candidate marker regions for loop-mediated isothermal amplification (LAMP) assays were identified from draft genomes of Calonectria henricotiae and C. pseudonaviculata, as well asmore » three related species not associated with this disease. To increase the probability of identifying unique targets, we used three approaches to mine genome datasets, based on (i) unique regions, (ii) polymorphisms, and (iii) presence/absence of regions across datasets. From a pool of candidate markers, we demonstrate LAMP assay specificity by testing related fungal species, common boxwood pathogens, and environmental samples containing 445 diverse fungal taxa. In conclusion, this comparative-genomics-based approach to the development of LAMP diagnostic assays is the first of its kind for fungi and could be easily applied to diagnostic marker development for other newly emergent plant pathogens.« less

Sentinel plant monitoring of Phytophthora ramorum at a research nursery over a six-year-period indicates limited aerial pathogen spread

Treesearch

Tomas Pastalka; Karen Suslow; Wolfgang Schweigkofler

2017-01-01

The National Ornamentals Research Site at Dominican University of California (NORS-DUC) is a research nursery that was established in 2009 to study invasive plant pathogens like Phytophthora ramorum, causal agent of sudden oak death and ramorum blight. In order to fulfill federal and state regulations, the possible...

Pseudomonas syringae pv. phaseolicola isolated from weeds in bean crop fields.

PubMed

Fernández-Sanz, A M; Rodicio, M R; González, A J

2016-04-01

Pseudomonas syringae pv. phaseolicola, the causative agent of halo blight in common bean (Phaseolus vulgaris L.), was isolated from weeds associated with bean crops in Spain. The bacterium was recovered from Fumaria sp, Mercurialis annua, Solanum nigrum and Sonchus oleraceus. Ps. s. pv. phaseolicola had previously been isolated from leguminous plants and S. nigrum, but to our knowledge, this is the first time it was recovered from the other three species. The isolates were phenotypically and genetically characterized, and they were compared with isolates recovered from common beans. Five different genotypic profiles were detected by PmeI-PFGE, two of them being of new description. Weed isolates were as pathogenic on bean plants as bean isolates, but they were not pathogenic on S. nigrum. Regarding the survival of the pathogen in weeds, Ps. s. pv. phaseolicola was isolated from So. oleraceus 11 weeks after the end of the bean crop. These results strongly support the idea of weeds as a potential source of inoculum for halo blight in bean. It has traditionally been considered that the main source of inoculum of Pseudomonas syringae pv. phaseolicola causing halo blight disease in Phaseolus vulgaris are the bean seeds, and that the host range of the bacterium is almost restricted to leguminous plants. In this study, the bacterium was recovered from four nonleguminous weed species collected in bean fields, and its permanence in weeds for at least 11 weeks after the harvesting of the beans was demonstrated. We have also proved that the strains isolated from weeds were pathogenic on bean plants. Accordingly, the host range of Ps. s. pv. phaseolicola could be broader than previously thought and weeds appear to be acting as a reservoir of the pathogen until the next crop. © 2016 The Society for Applied Microbiology.

Sequencing of the Litchi Downy Blight Pathogen Reveals It Is a Phytophthora Species With Downy Mildew-Like Characteristics.

PubMed

Ye, Wenwu; Wang, Yang; Shen, Danyu; Li, Delong; Pu, Tianhuizi; Jiang, Zide; Zhang, Zhengguang; Zheng, Xiaobo; Tyler, Brett M; Wang, Yuanchao

2016-07-01

On the basis of its downy mildew-like morphology, the litchi downy blight pathogen was previously named Peronophythora litchii. Recently, however, it was proposed to transfer this pathogen to Phytophthora clade 4. To better characterize this unusual oomycete species and important fruit pathogen, we obtained the genome sequence of Phytophthora litchii and compared it to those from other oomycete species. P. litchii has a small genome with tightly spaced genes. On the basis of a multilocus phylogenetic analysis, the placement of P. litchii in the genus Phytophthora is strongly supported. Effector proteins predicted included 245 RxLR, 30 necrosis-and-ethylene-inducing protein-like, and 14 crinkler proteins. The typical motifs, phylogenies, and activities of these effectors were typical for a Phytophthora species. However, like the genome features of the analyzed downy mildews, P. litchii exhibited a streamlined genome with a relatively small number of genes in both core and species-specific protein families. The low GC content and slight codon preferences of P. litchii sequences were similar to those of the analyzed downy mildews and a subset of Phytophthora species. Taken together, these observations suggest that P. litchii is a Phytophthora pathogen that is in the process of acquiring downy mildew-like genomic and morphological features. Thus P. litchii may provide a novel model for investigating morphological development and genomic adaptation in oomycete pathogens.

Some fungal endophytes from vegetable crops and their anti-oomycete activities against tomato late blight.

PubMed

Kim, H-Y; Choi, G J; Lee, H B; Lee, S-W; Lim, H K; Jang, K S; Son, S W; Lee, S O; Cho, K Y; Sung, N D; Kim, J-C

2007-03-01

To isolate endophytic fungi from vegetable plants and examine their in vivo anti-oomycete activity against Phytophthora infestans in tomato plants. Endophytic fungi were isolated from surface-sterilized plant tissues and anti-oomycete activity was measured by in vivo assay using tomato seedlings. Endophytic fungi showing potent anti-oomycete activity were identified by morphological characteristics and nuclear ribosomal ITS1-5.8S-ITS2 sequence analysis. A total of 152 isolates were obtained from 66 healthy tissue samples of cucumber, red pepper, tomato, pumpkin and Chinese cabbage and the fermentation broths of 23 isolates showed potent in vivo anti-oomycete activity against tomato late blight with control values over 90%. The Fusarium oxysporum strain EF119, which was isolated from roots of red pepper, showed the most potent disease control efficacy against tomato late blight. In dual-culture tests, it inhibited the growth of Pythium ultimum, P. infestans and Phytophthora capsici. Among endophytic fungi isolated from healthy tissues of vegetable plants, F. oxysporum EF119 showed the most potent in vivo anti-oomycete activity against tomato late blight and in vitro anti-oomycete activity against several oomycete pathogens. Endophytic fungi showing anti-oomycete activity in vitro and in vivo may be used as biocontrol agents particularly of tomato late blight.

Silencing of six susceptibility genes results in potato late blight resistance.

PubMed

Sun, Kaile; Wolters, Anne-Marie A; Vossen, Jack H; Rouwet, Maarten E; Loonen, Annelies E H M; Jacobsen, Evert; Visser, Richard G F; Bai, Yuling

2016-10-01

Phytophthora infestans, the causal agent of late blight, is a major threat to commercial potato production worldwide. Significant costs are required for crop protection to secure yield. Many dominant genes for resistance (R-genes) to potato late blight have been identified, and some of these R-genes have been applied in potato breeding. However, the P. infestans population rapidly accumulates new virulent strains that render R-genes ineffective. Here we introduce a new class of resistance which is based on the loss-of-function of a susceptibility gene (S-gene) encoding a product exploited by pathogens during infection and colonization. Impaired S-genes primarily result in recessive resistance traits in contrast to recognition-based resistance that is governed by dominant R-genes. In Arabidopsis thaliana, many S-genes have been detected in screens of mutant populations. In the present study, we selected 11 A. thaliana S-genes and silenced orthologous genes in the potato cultivar Desiree, which is highly susceptible to late blight. The silencing of five genes resulted in complete resistance to the P. infestans isolate Pic99189, and the silencing of a sixth S-gene resulted in reduced susceptibility. The application of S-genes to potato breeding for resistance to late blight is further discussed.

Cristulariella moricola associated with foliar blight of Camden white gum ( Eucalyptus benthamii ), a bioenergy crop

Treesearch

Doug P. Aubrey; Stephen W. Fraedrich; Thomas C. Harrington; Rabiu Olatinwo

2017-01-01

We report the association of Cristulariella moricola (Hino) Redhead with a zonate leaf spot on Eucalyptus benthamii (Myrtaceae). We observed the disease outbreak across a series of experimental E. benthamii plantings in Barnwell County, South Carolina, USA in October 2015. The disease caused nearly complete foliar necrosis of most trees in one experimental planting,...

Expression of leaf blight resistance in Brassica leafy greens under field conditions and inheritance of resistance in a Brassica juncea source

USDA-ARS?s Scientific Manuscript database

Brassica leafy greens are one of the most economically important vegetable commodities grown in the southeastern United States, and more than 28,000 metric tons of these crops are harvested in the U.S. annually. Collards and kale (Brassica oleracea L.), mustard greens (Brassica juncea L.) and turni...

Identification of quantitative trait Loci for resistance to southern leaf blight and days to anthesis in a maize recombinant inbred line population.

PubMed

Balint-Kurti, P J; Krakowsky, M D; Jines, M P; Robertson, L A; Molnár, T L; Goodman, M M; Holl, J B

2006-10-01

ABSTRACT A recombinant inbred line population derived from a cross between the maize lines NC300 (resistant) and B104 (susceptible) was evaluated for resistance to southern leaf blight (SLB) disease caused by Cochliobolus heterostrophus race O and for days to anthesis in four environments (Clayton, NC, and Tifton, GA, in both 2004 and 2005). Entry mean and average genetic correlations between disease ratings in different environments were high (0.78 to 0.89 and 0.9, respectively) and the overall entry mean heritability for SLB resistance was 0.89. When weighted mean disease ratings were fitted to a model using multiple interval mapping, seven potential quantitative trait loci (QTL) were identified, the two strongest being on chromosomes 3 (bin 3.04) and 9 (bin 9.03-9.04). These QTL explained a combined 80% of the phenotypic variation for SLB resistance. Some time-point-specific SLB resistance QTL were also identified. There was no significant correlation between disease resistance and days to anthesis. Six putative QTL for time to anthesis were identified, none of which coincided with any SLB resistance QTL.

Engineering super mycovirus donor strains of chestnut blight fungus by systematic disruption of multilocus vic genes.

PubMed

Zhang, Dong-Xiu; Nuss, Donald L

2016-02-23

Transmission of mycoviruses that attenuate virulence (hypovirulence) of pathogenic fungi is restricted by allorecognition systems operating in their fungal hosts. We report the use of systematic molecular gene disruption and classical genetics for engineering fungal hosts with superior virus transmission capabilities. Four of five diallelic virus-restricting allorecognition [vegetative incompatibility (vic)] loci were disrupted in the chestnut blight fungus Cryphonectria parasitica using an adapted Cre-loxP recombination system that allowed excision and recycling of selectable marker genes (SMGs). SMG-free, quadruple vic mutant strains representing both allelic backgrounds of the remaining vic locus were then produced through mating. In combination, these super donor strains were able to transmit hypoviruses to strains that were heteroallelic at one or all of the virus-restricting vic loci. These results demonstrate the feasibility of modulating allorecognition to engineer pathogenic fungi for more efficient transmission of virulence-attenuating mycoviruses and enhanced biological control potential.

A host basal transcription factor is a key component for infection of rice by TALE-carrying bacteria.

PubMed

Yuan, Meng; Ke, Yinggen; Huang, Renyan; Ma, Ling; Yang, Zeyu; Chu, Zhaohui; Xiao, Jinghua; Li, Xianghua; Wang, Shiping

2016-07-29

Transcription activator-like effectors (TALEs) are sequence-specific DNA binding proteins found in a range of plant pathogenic bacteria, where they play important roles in host-pathogen interactions. However, it has been unclear how TALEs, after they have been injected into the host cells, activate transcription of host genes required for infection success. Here, we show that the basal transcription factor IIA gamma subunit TFIIAγ5 from rice is a key component for infection by the TALE-carrying bacterium Xanthomonas oryzae pv. oryzae, the causal agent for bacterial blight. Direct interaction of several TALEs with TFIIAγ5 is required for activation of disease susceptibility genes. Conversely, reduced expression of the TFIIAγ5 host gene limits the induction of susceptibility genes and thus decreases bacterial blight symptoms. Suppression or mutation of TFIIAγ5 can also reduce bacterial streak, another devastating disease of rice caused by TALE-carrying X. oryzae pv. oryzicola. These results have important implications for formulating a widely applicable strategy with which to improve resistance of plants to TALE-carrying pathogens.

Microarray analysis of the semi-compatible pathogenic response and recovery of leafy spurge inoculated with the Cassava bacterial blight pathogen Xanthomonas axonopodis pv. manihotis

USDA-ARS?s Scientific Manuscript database

Infection by Xanthomonas axonopodis pv. manihotis (Xam)of the model perennial range land weed leafy spurge was tested to see if Xam might serve a potential biological control agent for this invasive weed. Although leafy spurge was susceptible to Xam infection, it recovered with 21 days after inocula...

Evolution of an invasive species research program and implications for large-scale management of a non-native, invasive plant pathogen

Treesearch

Christopher A. Lee; Janice M. Alexander; Susan J. Frankel; Yana Valachovic

2012-01-01

We conducted a research needs assessment (RNA) in 2010 to gather opinions of "experts" and a larger public on research priorities for Phytophthora ramorum, the pathogen that causes sudden oak death in forest trees and Ramorum blight in ornamental plants. We place these 2010 findings in context with findings of similar P. ramorum...

Brassinosteroid enhances resistance to fusarium diseases of barley.

PubMed

Ali, Shahin S; Kumar, G B Sunil; Khan, Mojibur; Doohan, Fiona M

2013-12-01

Fusarium pathogens are among the most damaging pathogens of cereals. These pathogens have the ability to attack the roots, seedlings, and flowering heads of barley and wheat plants with disease, resulting in yield loss and head blight disease and also resulting in the contamination of grain with mycotoxins harmful to human and animal health. There is increasing evidence that brassinosteroid (BR) hormones play an important role in plant defense against both biotic and abiotic stress agents and this study set out to determine if and how BR might affect Fusarium diseases of barley. Application of the epibrassinolide (epiBL) to heads of 'Lux' barley reduced the severity of Fusarium head blight (FHB) caused by Fusarium culmorum by 86% and reduced the FHB-associated loss in grain weight by 33%. Growth of plants in soil amended with epiBL resulted in a 28 and 35% reduction in Fusarium seedling blight (FSB) symptoms on the Lux and 'Akashinriki' barley, respectively. Microarray analysis was used to determine whether growth in epiBL-amended soil changed the transcriptional profile in stem base tissue during the early stages of FSB development. At 24 and 48 h post F. culmorum inoculation, there were 146 epiBL-responsive transcripts, the majority being from the 48-h time point (n = 118). Real-time reverse-transcription polymerase chain reaction analysis validated the results for eight transcripts, including five defense genes. The results of gene expression studies show that chromatin remodeling, hormonal signaling, photosynthesis, and pathogenesis-related genes are activated in plants as a result of growth in epiBL.

Lipid transfer proteins and protease inhibitors as key factors in the priming of barley responses to Fusarium head blight disease by a biocontrol strain of Pseudomonas fluorescens.

PubMed

Petti, Carloalberto; Khan, Mojibur; Doohan, Fiona

2010-11-01

Strains of non-pathogenic pseudomonad bacteria, can elicit host defence responses against pathogenic microorganisms. Pseudomonas fluorescens strain MKB158 can protect cereals from pathogenesis by Fusarium fungi, including Fusarium head blight which is an economically important disease due to its association with both yield loss and mycotoxin contamination of grain. Using the 22 K barley Affymetrix chip, trancriptome studies were undertaken to determine the local effect of P. fluorescens strain MKB158 on the transcriptome of barley head tissue, and to discriminate transcripts primed by the bacterium to respond to challenge by Fusarium culmorum, a causal agent of the economically important Fusarium head blight disease of cereals. The bacterium significantly affected the accumulation of 1203 transcripts and primed 74 to positively, and 14 to negatively, respond to the pathogen (P = 0.05). This is the first study to give insights into bacterium priming in the Triticeae tribe of grasses and associated transcripts were classified into 13 functional classes, associated with diverse functions, including detoxification, cell wall biosynthesis and the amplification of host defence responses. In silico analysis of Arabidopsis homologs of bacterium-primed barley genes indicated that, as is the case in dicots, jasmonic acid plays a role in pseudomonad priming of host responses. Additionally, the transcriptome studies described herein also reveal new insights into bacterium-mediated priming of host defences against necrotrophs, including the positive effects on grain filling, lignin deposition, oxidative stress responses, and the inhibition of protease inhibitors and proteins that play a key role in programmed cell death.

Lysozyme enhances the bactericidal effect of BP100 peptide against Erwinia amylovora, the causal agent of fire blight of rosaceous plants.

PubMed

Cabrefiga, Jordi; Montesinos, Emilio

2017-02-17

Fire blight is an important disease affecting rosaceous plants. The causal agent is the bacteria Erwinia amylovora which is poorly controlled with the use of conventional bactericides and biopesticides. Antimicrobial peptides (AMPs) have been proposed as a new compounds suitable for plant disease control. BP100, a synthetic linear undecapeptide (KKLFKKILKYL-NH 2 ), has been reported to be effective against E. amylovora infections. Moreover, BP100 showed bacteriolytic activity, moderate susceptibility to protease degradation and low toxicity. However, the peptide concentration required for an effective control of infections in planta is too high due to some inactivation by tissue components. This is a limitation beause of the high cost of synthesis of this compound. We expected that the combination of BP100 with lysozyme may produce a synergistic effect, enhancing its activity and reducing the effective concentration needed for fire blight control. The combination of a synhetic multifunctional undecapeptide (BP100) with lysozyme produces a synergistic effect. We showed a significant increase of the antimicrobial activity against E. amylovora that was associated to the increase of cell membrane damage and to the reduction of cell metabolism. Combination of BP100 with lysozyme reduced the time required to achieve cell death and the minimal inhibitory concentration (MIC), and increased the activity of BP100 in the presence of leaf extracts even when the peptide was applied at low doses. The results obtained in vitro were confirmed in leaf infection bioassays. The combination of BP100 with lysozyme showed synergism on the bactericidal activity against E. amylovora and provide the basis for developing better formulations of antibacterial peptides for plant protection.

Partial Resistance of Carrot to Alternaria dauci Correlates with In Vitro Cultured Carrot Cell Resistance to Fungal Exudates

PubMed Central

Voisine, Linda; Gatto, Julia; Hélesbeux, Jean-Jacques; Séraphin, Denis; Peña-Rodriguez, Luis M.; Richomme, Pascal; Boedo, Cora; Yovanopoulos, Claire; Gyomlai, Melvina; Briard, Mathilde; Simoneau, Philippe; Poupard, Pascal; Berruyer, Romain

2014-01-01

Although different mechanisms have been proposed in the recent years, plant pathogen partial resistance is still poorly understood. Components of the chemical warfare, including the production of plant defense compounds and plant resistance to pathogen-produced toxins, are likely to play a role. Toxins are indeed recognized as important determinants of pathogenicity in necrotrophic fungi. Partial resistance based on quantitative resistance loci and linked to a pathogen-produced toxin has never been fully described. We tested this hypothesis using the Alternaria dauci – carrot pathosystem. Alternaria dauci, causing carrot leaf blight, is a necrotrophic fungus known to produce zinniol, a compound described as a non-host selective toxin. Embryogenic cellular cultures from carrot genotypes varying in resistance against A. dauci were confronted with zinniol at different concentrations or to fungal exudates (raw, organic or aqueous extracts). The plant response was analyzed through the measurement of cytoplasmic esterase activity, as a marker of cell viability, and the differentiation of somatic embryos in cellular cultures. A differential response to toxicity was demonstrated between susceptible and partially resistant genotypes, with a good correlation noted between the resistance to the fungus at the whole plant level and resistance at the cellular level to fungal exudates from raw and organic extracts. No toxic reaction of embryogenic cultures was observed after treatment with the aqueous extract or zinniol used at physiological concentration. Moreover, we did not detect zinniol in toxic fungal extracts by UHPLC analysis. These results suggest that strong phytotoxic compounds are present in the organic extract and remain to be characterized. Our results clearly show that carrot tolerance to A. dauci toxins is one component of its partial resistance. PMID:24983469

Characterization of a new ViI-like Erwinia amylovora bacteriophage phiEa2809.

PubMed

Lagonenko, Alexander L; Sadovskaya, Olga; Valentovich, Leonid N; Evtushenkov, Anatoly N

2015-04-01

Erwinia amylovora is a Gram-negative plant pathogenic bacteria causing fire blight disease in many Rosaceae species. A novel E. amylovora bacteriophage, phiEa2809, was isolated from symptomless apple leaf sample collected in Belarus. This phage was also able to infect Pantoea agglomerans strains. The genome of phiEa2809 is a double-stranded linear DNA 162,160 bp in length, including 145 ORFs and one tRNA gene. The phiEa2809 genomic sequence is similar to the genomes of the Serratia plymutica phage MAM1, Shigella phage AG-3, Dickeya phage vB DsoM LIMEstone1 and Salmonella phage ViI and lacks similarity to described E. amylovora phage genomes. Based on virion morphology (an icosahedral head, long contractile tail) and genome structure, phiEa2809 was classified as a member of Myoviridae, ViI-like bacteriophages group. PhiEa2809 is the firstly characterized ViI-like bacteriophage able to lyse E. amylovora. © FEMS 2015. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Deletion and Complementation of the Mating Type (MAT) Locus of the Wheat Head Blight Pathogen Gibberella zeae

PubMed Central

Desjardins, A. E.; Brown, D. W.; Yun, S.-H.; Proctor, R. H.; Lee, T.; Plattner, R. D.; Lu, S.-W.; Turgeon, B. G.

2004-01-01

Gibberella zeae, a self-fertile, haploid filamentous ascomycete, causes serious epidemics of wheat (Triticum aestivum) head blight worldwide and contaminates grain with trichothecene mycotoxins. Anecdotal evidence dating back to the late 19th century indicates that G. zeae ascospores (sexual spores) are a more important inoculum source than are macroconidia (asexual spores), although the fungus can produce both during wheat head blight epidemics. To develop fungal strains to test this hypothesis, the entire mating type (MAT1) locus was deleted from a self-fertile (MAT1-1/MAT1-2), virulent, trichothecene-producing wild-type strain of G. zeae. The resulting MAT deletion (mat1-1/mat1-2) strains were unable to produce perithecia or ascospores and appeared to be unable to mate with the fertile strain from which they were derived. Complementation of a MAT deletion strain by transformation with a copy of the entire MAT locus resulted in recovery of production of perithecia and ascospores. MAT deletion strains and MAT-complemented strains retained the ability to produce macroconidia that could cause head blight, as assessed by direct injection into wheat heads in greenhouse tests. Availability of MAT-null and MAT-complemented strains provides a means to determine the importance of ascospores in the biology of G. zeae and perhaps to identify novel approaches to control wheat head blight. PMID:15066842

Isolation and characterization of rhizosphere bacteria for the biocontrol of the damping-off disease of tomatoes in Tunisia.

PubMed

Hammami, Inés; Ben Hsouna, Anis; Hamdi, Naceur; Gdoura, Radhouane; Triki, Mohamed Ali

2013-01-01

Fluorescent Pseudomonas spp., isolated from tomato and pepper plants rhizosphere soil, was evaluated in vitro as a potential antagonist of fungal pathogens. Pseudomonas strains were tested against the causal agents of tomatoes damping-off (Sclerotinia sclerotiorum), root rot (Fusarium solani), and causal agents of stem canker and leaf blight (Alternaria alternata). For this purpose, dual culture antagonism assays were carried out on 25% tryptic soy agar, King B medium and potato dextrose agar to determine the effect of the strains on mycelial growth of the pathogens. In addition, strains were screened for their ability to produce exoenzymes and siderophores. All the strains significantly inhibited Alternaria alternata, particularly in 25% TSA medium. Antagonistic effect on Sclerotinia sclerotiorum and Fusarium solani was greater on King B medium. Protease was produced by 30% of the strains, but no strain produced cellulase or chitinase. Finally, the selected Pseudomonas strain, Psf5, was evaluated on tomato seedling development and as a potential candidate for controlling tomato damping-off caused by Sclerotinia sclerotiorum, under growth chamber conditions. In vivo studies resulted in significant increases in plant stand as well as in root dry weight. Psf5 was able to establish and survive in tomato plants rhizosphere after 40days following the planting of bacterized seeds. © 2013 Académie des sciences. Published by Elsevier SAS. All rights reserved.

Hypersensitive response and acyl‐homoserine lactone production of the fire blight antagonists Erwinia tasmaniensis and Erwinia billingiae

PubMed Central

Jakovljevic, Vladimir; Jock, Susanne; Du, Zhiqiang; Geider, Klaus

2008-01-01

Summary Fire blight caused by the Gram‐negative bacterium Erwinia amylovora can be controlled by antagonistic microorganisms. We characterized epiphytic bacteria isolated from healthy apple and pear trees in Australia, named Erwinia tasmaniensis, and the epiphytic bacterium Erwinia billingiae from England for physiological properties, interaction with plants and interference with growth of E. amylovora. They reduced symptom formation by the fire blight pathogen on immature pears and the colonization of apple flowers. In contrast to E. billingiae, E. tasmaniensis strains induced a hypersensitive response in tobacco leaves and synthesized levan in the presence of sucrose. With consensus primers deduced from lsc as well as hrpL, hrcC and hrcR of the hrp region of E. amylovora and of related bacteria, these genes were successfully amplified from E. tasmaniensis DNA and alignment of the encoded proteins to other Erwinia species supported a role for environmental fitness of the epiphytic bacterium. Unlike E. tasmaniensis, the epiphytic bacterium E. billingiae produced an acyl‐homoserine lactone for bacterial cell‐to‐cell communication. Their competition with the growth of E. amylovora may be involved in controlling fire blight. PMID:21261861

Gene silencing using the recessive rice bacterial blight resistance gene xa13 as a new paradigm in plant breeding.

PubMed

Li, Changyan; Wei, Jing; Lin, Yongjun; Chen, Hao

2012-05-01

Resistant germplasm resources are valuable for developing resistant varieties in agricultural production. However, recessive resistance genes are usually overlooked in hybrid breeding. Compared with dominant traits, however, they may confer resistance to different pathogenic races or pest biotypes with different mechanisms of action. The recessive rice bacterial blight resistance gene xa13, also involved in pollen development, has been cloned and its resistance mechanism has been recently characterized. This report describes the conversion of bacterial blight resistance mediated by the recessive xa13 gene into a dominant trait to facilitate its use in a breeding program. This was achieved by knockdown of the corresponding dominant allele Xa13 in transgenic rice using recently developed artificial microRNA technology. Tissue-specific promoters were used to exclude most of the expression of artificial microRNA in the anther to ensure that Xa13 functioned normally during pollen development. A battery of highly bacterial blight resistant transgenic plants with normal seed setting rates were acquired, indicating that highly specific gene silencing had been achieved. Our success with xa13 provides a paradigm that can be adapted to other recessive resistance genes.

The cold-induced defensin TAD1 confers resistance against snow mold and Fusarium head blight in transgenic wheat.

PubMed

Sasaki, Kentaro; Kuwabara, Chikako; Umeki, Natsuki; Fujioka, Mari; Saburi, Wataru; Matsui, Hirokazu; Abe, Fumitaka; Imai, Ryozo

2016-06-20

TAD1 (Triticum aestivum defensin 1) is induced during cold acclimation in winter wheat and encodes a plant defensin with antimicrobial activity. In this study, we demonstrated that recombinant TAD1 protein inhibits hyphal growth of the snow mold fungus, Typhula ishikariensis in vitro. Transgenic wheat plants overexpressing TAD1 were created and tested for resistance against T. ishikariensis. Leaf inoculation assays revealed that overexpression of TAD1 confers resistance against the snow mold. In addition, the TAD1-overexpressors showed resistance against Fusarium graminearum, which causes Fusarium head blight, a devastating disease in wheat and barley. These results indicate that TAD1 is a candidate gene to improve resistance against multiple fungal diseases in cereal crops. Copyright © 2016 Elsevier B.V. All rights reserved.

PCR-Mediated Detection and Quantification of the Goss's Wilt Pathogen Clavibacter michiganensis subsp. nebraskensis Via a Novel Gene Target.

PubMed

McNally, R Ryan; Ishimaru, Carol A; Malvick, Dean K

2016-12-01

Goss's leaf blight and wilt of maize (corn) is a significant and reemerging disease caused by the bacterium Clavibacter michiganensis subsp. nebraskensis. Despite its importance, molecular tools for diagnosing and studying this disease remain limited. We report the identification of CMN_01184 as a novel gene target and its use in conventional PCR (cPCR) and SYBR green-based quantitative PCR (qPCR) assays for specific detection and quantification of C. michiganensis subsp. nebraskensis. The cPCR and qPCR assays based on primers targeting CMN_01184 specifically amplified only C. michiganensis subsp. nebraskensis among a diverse collection of 129 bacterial and fungal isolates, including multiple maize bacterial and fungal pathogens, environmental organisms from agricultural fields, and all known subspecies of C. michiganensis. Specificity of the assays for detection of only C. michiganensis subsp. nebraskensis was also validated with field samples of C. michiganensis subsp. nebraskensis-infected and uninfected maize leaves and C. michiganensis subsp. nebraskensis-infested and uninfested soil. Detection limits were determined at 30 and 3 ng of pure C. michiganensis subsp. nebraskensis DNA, and 100 and 10 CFU of C. michiganensis subsp. nebraskensis for the cPCR and qPCR assays, respectively. Infection of maize leaves by C. michiganensis subsp. nebraskensis was quantified from infected field samples and was standardized using an internal maize DNA control. These novel, specific, and sensitive PCR assays based on CMN_01184 are effective for diagnosis of Goss's wilt and for studies of the epidemiology and host-pathogen interactions of C. michiganensis subsp. nebraskensis.

Characterization of effectors from Fusarium graminearum

USDA-ARS?s Scientific Manuscript database

Fusarium graminearum is the causal agent of Fusarium head blight (FHB), which reduces crop yield and quality by producing various mycotoxins. Effectors play an important role in the pathogenesis of many bacterial and fungal pathogens. In this study, 26 effector candidates were selected for investiga...

ATTX961014-1R/Y a.k.a. Sierra Rose: A red skin, yellow flesh cultivar for the specialty/gourmet market

USDA-ARS?s Scientific Manuscript database

ATTX961014-1R/Y is a high yielding, red skin, yellow flesh cultivar which was released by Texas A&M AgriLife Research in 2012. It resulted from a cross of breeding clone A90601-2RDY by the potato cultivar Mazama. ATTX961014-1R/Y is susceptible to Late Blight (Phytopthora infestans), Potato Leaf Roll...

RNA-Seq analysis reveals insight into enhanced rice Xa7-mediated bacterial blight resistance at high temperature.

PubMed

Cohen, Stephen P; Liu, Hongxia; Argueso, Cristiana T; Pereira, Andy; Vera Cruz, Casiana; Verdier, Valerie; Leach, Jan E

2017-01-01

Plant disease is a major challenge to agriculture worldwide, and it is exacerbated by abiotic environmental factors. During some plant-pathogen interactions, heat stress allows pathogens to overcome host resistance, a phenomenon which could severely impact crop productivity considering the global warming trends associated with climate change. Despite the importance of this phenomenon, little is known about the underlying molecular mechanisms. To better understand host plant responses during simultaneous heat and pathogen stress, we conducted a transcriptomics experiment for rice plants (cultivar IRBB61) containing Xa7, a bacterial blight disease resistance (R) gene, that were infected with Xanthomonas oryzae, the bacterial blight pathogen of rice, during high temperature stress. Xa7-mediated resistance is unusual relative to resistance mediated by other R genes in that it functions better at high temperatures. Using RNA-Seq technology, we identified 8,499 differentially expressed genes as temperature responsive in rice cultivar IRBB61 experiencing susceptible and resistant interactions across three time points. Notably, genes in the plant hormone abscisic acid biosynthesis and response pathways were up-regulated by high temperature in both mock-treated plants and plants experiencing a susceptible interaction and were suppressed by high temperature in plants exhibiting Xa7-mediated resistance. Genes responsive to salicylic acid, an important plant hormone for disease resistance, were down-regulated by high temperature during both the susceptible and resistant interactions, suggesting that enhanced Xa7-mediated resistance at high temperature is not dependent on salicylic acid signaling. A DNA sequence motif similar to known abscisic acid-responsive cis-regulatory elements was identified in the promoter region upstream of genes up-regulated in susceptible but down-regulated in resistant interactions. The results of our study suggest that the plant hormone abscisic acid is an important node for cross-talk between plant transcriptional response pathways to high temperature stress and pathogen attack. Genes in this pathway represent an important focus for future study to determine how plants evolved to deal with simultaneous abiotic and biotic stresses.

RNA-Seq analysis reveals insight into enhanced rice Xa7-mediated bacterial blight resistance at high temperature

PubMed Central

Argueso, Cristiana T.; Pereira, Andy; Vera Cruz, Casiana; Verdier, Valerie

2017-01-01

Plant disease is a major challenge to agriculture worldwide, and it is exacerbated by abiotic environmental factors. During some plant-pathogen interactions, heat stress allows pathogens to overcome host resistance, a phenomenon which could severely impact crop productivity considering the global warming trends associated with climate change. Despite the importance of this phenomenon, little is known about the underlying molecular mechanisms. To better understand host plant responses during simultaneous heat and pathogen stress, we conducted a transcriptomics experiment for rice plants (cultivar IRBB61) containing Xa7, a bacterial blight disease resistance (R) gene, that were infected with Xanthomonas oryzae, the bacterial blight pathogen of rice, during high temperature stress. Xa7-mediated resistance is unusual relative to resistance mediated by other R genes in that it functions better at high temperatures. Using RNA-Seq technology, we identified 8,499 differentially expressed genes as temperature responsive in rice cultivar IRBB61 experiencing susceptible and resistant interactions across three time points. Notably, genes in the plant hormone abscisic acid biosynthesis and response pathways were up-regulated by high temperature in both mock-treated plants and plants experiencing a susceptible interaction and were suppressed by high temperature in plants exhibiting Xa7-mediated resistance. Genes responsive to salicylic acid, an important plant hormone for disease resistance, were down-regulated by high temperature during both the susceptible and resistant interactions, suggesting that enhanced Xa7-mediated resistance at high temperature is not dependent on salicylic acid signaling. A DNA sequence motif similar to known abscisic acid-responsive cis-regulatory elements was identified in the promoter region upstream of genes up-regulated in susceptible but down-regulated in resistant interactions. The results of our study suggest that the plant hormone abscisic acid is an important node for cross-talk between plant transcriptional response pathways to high temperature stress and pathogen attack. Genes in this pathway represent an important focus for future study to determine how plants evolved to deal with simultaneous abiotic and biotic stresses. PMID:29107972

Defining species boundaries in the genus Phytophthora: the case of Phytophthora andina. A response to “Phytophthora andina sp. nov., a newly identified heterothallic pathogen of solanaceous hosts in the Andean highlands

USDA-ARS?s Scientific Manuscript database

The newly described species Phytophthora andina is a relative of the potato late blight pathogen P. infestans. The formal P. andina species description is based on three types of evidence. First, the fact that these Ecuadorian isolates were found causing disease on different wild Solanum spp. that a...

A host basal transcription factor is a key component for infection of rice by TALE-carrying bacteria

PubMed Central

Yuan, Meng; Ke, Yinggen; Huang, Renyan; Ma, Ling; Yang, Zeyu; Chu, Zhaohui; Xiao, Jinghua; Li, Xianghua; Wang, Shiping

2016-01-01

Transcription activator-like effectors (TALEs) are sequence-specific DNA binding proteins found in a range of plant pathogenic bacteria, where they play important roles in host-pathogen interactions. However, it has been unclear how TALEs, after they have been injected into the host cells, activate transcription of host genes required for infection success. Here, we show that the basal transcription factor IIA gamma subunit TFIIAγ5 from rice is a key component for infection by the TALE-carrying bacterium Xanthomonas oryzae pv. oryzae, the causal agent for bacterial blight. Direct interaction of several TALEs with TFIIAγ5 is required for activation of disease susceptibility genes. Conversely, reduced expression of the TFIIAγ5 host gene limits the induction of susceptibility genes and thus decreases bacterial blight symptoms. Suppression or mutation of TFIIAγ5 can also reduce bacterial streak, another devastating disease of rice caused by TALE-carrying X. oryzae pv. oryzicola. These results have important implications for formulating a widely applicable strategy with which to improve resistance of plants to TALE-carrying pathogens. DOI: http://dx.doi.org/10.7554/eLife.19605.001 PMID:27472897

Novel FHB control strategy using the volatile trichodiene to reduce mycotoxins

USDA-ARS?s Scientific Manuscript database

Fusarium graminearum (Fg), the primary fungal pathogen responsible for Fusarium head blight (FHB), reduces crop yield and contaminates grain with trichothecene mycotoxins that are deleterious to plant, human and animal health. The first committed step in trichothecene biosynthesis is the formation o...

Bioprospecting endophytic diazotrophic Lysinibacillus sphaericus as biocontrol agents of rice sheath blight disease.

PubMed

Shabanamol, S; Sreekumar, J; Jisha, M S

2017-10-01

The present study tried to explore the possible in vitro biocontrol mechanisms of Lysinibacillus sphaericus , a diazotrophic endophyte from rice against the rice sheath blight pathogen Rhizoctonia solani. The in vivo biocontrol potential of the isolate and the induction of systemic resistance under greenhouse conditions have also been experimented employing different treatments with positive control carbendazim, the chemical fungicide. The endophytic isolate showed 100% growth inhibition of the fungal pathogen via volatile organic compound production and was positive for the production of siderophores, biosurfactants, HCN, and ammonia. Under greenhouse conditions, foliar and soil application of L. sphaericus significantly decreased the percentage of disease incidence. All bacterized treatments are superior to chemical fungicide treatment. Application of L. sphaericus in single and combination treatments induces systemic resistance as evident from the significant accumulation of defense enzymes such as peroxides, polyphenol oxides and phenylalanine ammonia in addition to the increase of phenolic compounds. The results biologically prospect endophytic diazotroph L. sphaericus as a potent plant growth promoter with excellent biocontrol efficiency.

Engineering fire blight resistance into the apple cultivar 'Gala' using the FB_MR5 CC-NBS-LRR resistance gene of Malus × robusta 5.

PubMed

Broggini, Giovanni A L; Wöhner, Thomas; Fahrentrapp, Johannes; Kost, Thomas D; Flachowsky, Henryk; Peil, Andreas; Hanke, Maria-Viola; Richter, Klaus; Patocchi, Andrea; Gessler, Cesare

2014-08-01

The fire blight susceptible apple cultivar Malus × domestica Borkh. cv. 'Gala' was transformed with the candidate fire blight resistance gene FB_MR5 originating from the crab apple accession Malus × robusta 5 (Mr5). A total of five different transgenic lines were obtained. All transgenic lines were shown to be stably transformed and originate from different transgenic events. The transgenic lines express the FB_MR5 either driven by the constitutive CaMV 35S promoter and the ocs terminator or by its native promoter and terminator sequences. Phenotyping experiments were performed with Mr5-virulent and Mr5-avirulent strains of Erwinia amylovora, the causal agent of fire blight. Significantly less disease symptoms were detected on transgenic lines after inoculation with two different Mr5-avirulent E. amylovora strains, while significantly more shoot necrosis was observed after inoculation with the Mr5-virulent mutant strain ZYRKD3_1. The results of these experiments demonstrated the ability of a single gene isolated from the native gene pool of apple to protect a susceptible cultivar from fire blight. Furthermore, this gene is confirmed to be the resistance determinant of Mr5 as the transformed lines undergo the same gene-for-gene interaction in the host-pathogen relationship Mr5-E. amylovora. © 2014 Society for Experimental Biology, Association of Applied Biologists and John Wiley & Sons Ltd.

Thiamine primed defense provides reliable alternative to systemic fungicide carbendazim against sheath blight disease in rice (Oryza sativa L.).

PubMed

Bahuguna, Rajeev Nayan; Joshi, Rohit; Shukla, Alok; Pandey, Mayank; Kumar, J

2012-08-01

A novel pathogen defense strategy by thiamine priming was evaluated for its efficacy against sheath blight pathogen, Rhizoctonia solani AG-1A, of rice and compared with that of systemic fungicide, carbendazim (BCM). Seeds of semidwarf, high yielding, basmati rice variety Vasumati were treated with thiamine (50 mM) and BCM (4 mM). The pot cultured plants were challenge inoculated with R. solani after 40 days of sowing and effect of thiamine and BCM on rice growth and yield traits was examined. Higher hydrogen peroxide content, total phenolics accumulation, phenylalanine ammonia lyase (PAL) activity and superoxide dismutase (SOD) activity under thiamine treatment displayed elevated level of systemic resistance, which was further augmented under challenging pathogen infection. High transcript level of phenylalanine ammonia lyase (PAL) and manganese superoxide dismutase (MnSOD) validated mode of thiamine primed defense. Though minimum disease severity was observed under BCM treatment, thiamine produced comparable results, with 18.12 per cent lower efficacy. Along with fortifying defense components and minor influence on photosynthetic pigments and nitrate reductase (NR) activity, thiamine treatment significantly reduced pathogen-induced loss in photosynthesis, stomatal conductance, chlorophyll fluorescence, NR activity and NR transcript level. Physiological traits affected under pathogen infection were found signatory for characterizing plant's response under disease and were detectable at early stage of infection. These findings provide a novel paradigm for developing alternative, environmentally safe strategies to control plant diseases. Copyright © 2012 Elsevier Masson SAS. All rights reserved.

Large-spored Alternaria pathogens in section Porri disentangled

PubMed Central

Woudenberg, J.H.C.; Truter, M.; Groenewald, J.Z.; Crous, P.W.

2014-01-01

The omnipresent fungal genus Alternaria was recently divided into 24 sections based on molecular and morphological data. Alternaria sect. Porri is the largest section, containing almost all Alternaria species with medium to large conidia and long beaks, some of which are important plant pathogens (e.g. Alternaria porri, A. solani and A. tomatophila). We constructed a multi-gene phylogeny on parts of the ITS, GAPDH, RPB2, TEF1 and Alt a 1 gene regions, which, supplemented with morphological and cultural studies, forms the basis for species recognition in sect. Porri. Our data reveal 63 species, of which 10 are newly described in sect. Porri, and 27 species names are synonymised. The three known Alternaria pathogens causing early blight on tomato all cluster in one clade, and are synonymised under the older name, A. linariae. Alternaria protenta, a species formerly only known as pathogen on Helianthus annuus, is also reported to cause early blight of potato, together with A. solani and A. grandis. Two clades with isolates causing purple blotch of onion are confirmed as A. allii and A. porri, but the two species cannot adequately be distinguished based on the number of beaks and branches as suggested previously. This is also found among the pathogens of Passifloraceae, which are reduced from four to three species. In addition to the known pathogen of sweet potato, A. bataticola, three more species are delineated of which two are newly described. A new Alternaria section is also described, comprising two large-spored Alternaria species with concatenate conidia. PMID:25492985

Large-spored Alternaria pathogens in section Porri disentangled.

PubMed

Woudenberg, J H C; Truter, M; Groenewald, J Z; Crous, P W

2014-09-01

The omnipresent fungal genus Alternaria was recently divided into 24 sections based on molecular and morphological data. Alternaria sect. Porri is the largest section, containing almost all Alternaria species with medium to large conidia and long beaks, some of which are important plant pathogens (e.g. Alternaria porri, A. solani and A. tomatophila). We constructed a multi-gene phylogeny on parts of the ITS, GAPDH, RPB2, TEF1 and Alt a 1 gene regions, which, supplemented with morphological and cultural studies, forms the basis for species recognition in sect. Porri. Our data reveal 63 species, of which 10 are newly described in sect. Porri, and 27 species names are synonymised. The three known Alternaria pathogens causing early blight on tomato all cluster in one clade, and are synonymised under the older name, A. linariae. Alternaria protenta, a species formerly only known as pathogen on Helianthus annuus, is also reported to cause early blight of potato, together with A. solani and A. grandis. Two clades with isolates causing purple blotch of onion are confirmed as A. allii and A. porri, but the two species cannot adequately be distinguished based on the number of beaks and branches as suggested previously. This is also found among the pathogens of Passifloraceae, which are reduced from four to three species. In addition to the known pathogen of sweet potato, A. bataticola, three more species are delineated of which two are newly described. A new Alternaria section is also described, comprising two large-spored Alternaria species with concatenate conidia.

Genetic population structure of Fusarium graminearum species complex in Korean cereals

USDA-ARS?s Scientific Manuscript database

Small grain cereals are frequently contaminated with toxigenic Fusarium species. Members of the Fusarium graminearum species complex (FGSC) are known as a head blight pathogens and mycotoxin producers. In order to characterize the FGSC populations associated with cereals in Korea, barley, corn, maiz...

Comparative and bioinformatics analyses of pathogenic bacterial secretomes identified by mass spectrometry in Burkholderia species.

PubMed

Nguyen, Thao Thi; Chon, Tae-Soo; Kim, Jaehan; Seo, Young-Su; Heo, Muyoung

2017-07-01

Secreted proteins (secretomes) play crucial roles during bacterial pathogenesis in both plant and human hosts. The identification and characterization of secretomes in the two plant pathogens Burkholderia glumae BGR1 and B. gladioli BSR3, which cause diseases in rice such as seedling blight, panicle blight, and grain rot, are important steps to not only understand the disease-causing mechanisms but also find remedies for the diseases. Here, we identified two datasets of secretomes in B. glumae BGR1 and B. gladioli BSR3, which consist of 118 and 111 proteins, respectively, using mass spectrometry approach and literature curation. Next, we characterized the functional properties, potential secretion pathways and sequence information properties of secretomes of two plant pathogens in a comparative analysis by various computational approaches. The ratio of potential non-classically secreted proteins (NCSPs) to classically secreted proteins (CSPs) in B. glumae BGR1 was greater than that in B. gladioli BSR3. For CSPs, the putative hydrophobic regions (PHRs) which are essential for secretion process of CSPs were screened in detail at their N-terminal sequences using hidden Markov model (HMM)-based method. Total 31 pairs of homologous proteins in two bacterial secretomes were indicated based on the global alignment (identity ≥ 70%). Our results may facilitate the understanding of the species-specific features of secretomes in two plant pathogenic Burkholderia species.

Pseudomonas orientalis F9: A Potent Antagonist against Phytopathogens with Phytotoxic Effect in the Apple Flower

PubMed Central

Zengerer, Veronika; Schmid, Michael; Bieri, Marco; Müller, Denise C.; Remus-Emsermann, Mitja N. P.; Ahrens, Christian H.; Pelludat, Cosima

2018-01-01

In light of public concerns over the use of pesticides and antibiotics in plant protection and the subsequent selection for spread of resistant bacteria in the environment, it is inevitable to broaden our knowledge about viable alternatives, such as natural antagonists and their mode of action. The genus Pseudomonas is known for its metabolic versatility and genetic plasticity, encompassing pathogens as well as antagonists. We characterized strain Pseudomonas orientalis F9, an isolate from apple flowers in a Swiss orchard, and determined its antagonistic activity against several phytopathogenic bacteria, in particular Erwinia amylovora, the causal agent of fire blight. P. orientalis F9 displayed antagonistic activity against a broad suite of phytopathogenic bacteria in the in vitro tests. The promising results from this analysis led to an ex vivo assay with E. amylovora CFBP1430Rif and P. orientalis F9 infected detached apple flowers. F9 diminished the fire blight pathogen in the flowers but also revealed phytotoxic traits. The experimental results were discussed in light of the complete genome sequence of F9, which revealed the strain to carry phenazine genes. Phenazines are known to contribute to antagonistic activity of bacterial strains against soil pathogens. When tested in the cress assay with Pythium ultimum as pathogen, F9 showed results comparable to the known antagonist P. protegens CHA0. PMID:29479340

Dissemination of aerial and root infecting Phytophthoras by human vectors

Treesearch

J.F. Webber; J. Rose

2008-01-01

Two new Phytophthora pathogens, Phytophthora kernoviae and P. ramorum, have recently established in parts of the U.K. They are most prevalent in the south west of England where they cause intense episodes of foliar blight and dieback on both ornamental and naturalised rhododendron such as Rhododendron ponticum,...

Rooting Response of Azalea Cultivars Using Hot Water Treatments to Control Pathogens

USDA-ARS?s Scientific Manuscript database

Azalea web blight is an annual problem on some evergreen azalea cultivars grown in containerized nursery production in the southern and eastern United States. The binucleate Rhizoctonia species, which cause the disease, are spread on new shoot growth harvested for propagation. Rhizoctonia can be eli...

Structural and Functional Characterization of TRI3 Acetyltransferase from Fusarium sporotrichioides

USDA-ARS?s Scientific Manuscript database

Fusarium Head Blight (FHB) is a devastating disease of cereal crops whose worldwide incidence is increasing and at present there is no satisfactory way of combating this pathogen or its associated toxins. There is a wide variety of trichothecene mycotoxins and they all contain a 12,13-epoxytrichoth...

Complete genome sequence of the plant pathogen Erwinia amylovora strain ATCC 49946

USDA-ARS?s Scientific Manuscript database

Erwinia amylovora causes the economically important disease fire blight that affects rosaceous plants, especially pear and apple. Here we report the complete genome sequence and annotation of strain ATCC 49946. The analysis of the sequence and its comparison with sequenced genomes of closely related...

Diversity of Fusarium head blight populations and trichothecene toxin types reveals regional differences in pathogen composition and temporal dynamics

USDA-ARS?s Scientific Manuscript database

Analyses of genetic diversity, trichothecene genotype composition, and population structure were conducted using 4,086 Fusarium graminearum isolates collected from wheat in eight Canadian provinces over a three year period between 2005 and 2007. The results revealed substantial regional differences ...

The implications of American chestnut reintroduction on landscape dynamics and carbon storage

Treesearch

Eric J. Gustafson; Arjan de Bruijn; Nathanael Lichti; Douglass F. Jacobs; Brian R. Sturtevant; Jane Foster; Brian R. Miranda; Harmony J. Dalgleish

2017-01-01

In the eastern United States, American chestnut (Castanea dentata) was historically a major component of forest communities, but was functionally extirpated in the early 20th century by an introduced pathogen, chestnut blight (Cryphonectria parasitica). Because chestnut is fast-growing, long-lived, and resistant to decay,...

The Silvics of Castanea dentata (Marsh.) Borkh., American chestnut, Fagaceae (Beech Family)

Treesearch

G. Geoff Wang; Benjamin O. Knapp; Stacy L. Clark; Bryan T. Mudder

2013-01-01

This report describes how the American chestnut (Castanea dentata) was ecologically extirpated due to an exotic pathogen, the chestnut blight (Cryphonectria parasitica), and describes current restoration efforts. The habitat, life history, special uses, and genetics of the American chestnut are detailed. The American chestnut was...

Winter Iinjury of American chestnut seedlings grown in a common garden at the species' northern range limit

Treesearch

Paul G. Schaberg; Thomas M. Saielli; Gary J. Hawley; Joshua M. Halman; Kendra M. Gurney

2013-01-01

Hybridization of American chestnut (Castanea dentata) with Chinese chestnut (C. mollissima), followed by backcrossing to American chestnut, is conducted to increase the resistance of resulting stock to chestnut blight, caused by the fungal pathogen Cryphonectria parasitica (Murr.) Barr. Backcross breeding is...

Compartmentalized gene regulatory network of the pathogenic fungus Fusarium graminearum

USDA-ARS?s Scientific Manuscript database

Head blight caused by Fusarium graminearum (Fg) is a major limiting factor of wheat production with both yield loss and mycotoxin contamination. Here we report a model for global Fg gene regulatory networks (GRNs) inferred from a large collection of transcriptomic data using a machine-learning appro...

Gene-for-gene relationship in the host-pathogen system Malus × robusta 5-Erwinia amylovora.

PubMed

Vogt, Isabelle; Wöhner, Thomas; Richter, Klaus; Flachowsky, Henryk; Sundin, George W; Wensing, Annette; Savory, Elizabeth A; Geider, Klaus; Day, Brad; Hanke, Magda-Viola; Peil, Andreas

2013-03-01

Fire blight is a destructive bacterial disease caused by Erwinia amylovora affecting plants in the family Rosaceae, including apple. Host resistance to fire blight is present mainly in accessions of Malus spp. and is thought to be quantitative in this pathosystem. In this study we analyzed the importance of the E. amylovora effector avrRpt2(EA) , a homolog of Pseudomonas syringae avrRpt2, for resistance of Malus × robusta 5 (Mr5). The deletion mutant E. amylovora Ea1189ΔavrRpt2(EA) was able to overcome the fire blight resistance of Mr5. One single nucleotide polymorphism (SNP), resulting in an exchange of cysteine to serine in the encoded protein, was detected in avrRpt2(EA) of several Erwinia strains differing in virulence to Mr5. E. amylovora strains encoding serine (S-allele) were able to overcome resistance of Mr5, whereas strains encoding cysteine (C-allele) were not. Allele specificity was also observed in a coexpression assay with Arabidopsis thaliana RIN4 in Nicotiana benthamiana. A homolog of RIN4 has been detected and isolated in Mr5. These results suggest a system similar to the interaction of RPS2 from A. thaliana and AvrRpt2 from P. syringae with RIN4 as guard. Our data are suggestive of a gene-for-gene relationship for the host-pathogen system Mr5 and E. amylovora. No claim to original US government works. New Phytologist © 2013 New Phytologist Trust.

Polyethylene mulch modifies greenhouse microclimate and reduces infection of phytophthora infestans in tomato and Pseudoperonospora cubensis in cucumber.

PubMed

Shtienberg, D; Elad, Y; Bornstein, M; Ziv, G; Grava, A; Cohen, S

2010-01-01

The individual and joint effects of covering the soil with polyethylene mulch before planting and fungicides commonly used by organic growers on tomato late blight (caused by Phytophthora infestans) were studied in three experiments conducted from 2002 to 2005. Application of fungicides resulted in inconsistent and insufficient late blight suppression (control efficacy +/- standard error of 34.5 +/- 14.3%) but the polyethylene mulch resulted in consistent, effective, and highly significant suppression (control efficacy of 83.6 +/- 5.5%) of the disease. The combined effect of the two measures was additive. In a second set of three experiments carried out between 2004 and 2006, it was found that the type of polyethylene mulch used (bicolor aluminized, clear, or black) did not affect the efficacy of late blight suppression (control efficacy of 60.1 to 95.8%) and the differences in the effects among the different polyethylene mulches used were insignificant. Next, the ability of the mulch to suppress cucumber downy mildew (caused by Pseudoperonospora cubensis) was studied in four experiments carried out between 2006 and 2008. The mulch effectively suppressed cucumber downy mildew but the effect was less substantial (control efficacy of 34.9 +/- 4.8%) than that achieved for tomato late blight. The disease-suppressing effect of mulch appeared to come from a reduction in leaf wetness duration, because mulching led to reductions in both the frequency of nights when dew formed and the number of dew hours per night when it formed. Mulching also reduced relative humidity in the canopy, which may have reduced sporulation.

Characterization and antagonistic properties of Streptomyces strains isolated from Saharan soils, and evaluation of their ability to control seedling blight of barley caused by Fusarium culmorum.

PubMed

Yekkour, A; Sabaou, N; Zitouni, A; Errakhi, R; Mathieu, F; Lebrihi, A

2012-12-01

During a screening for potential plant disease control actinomycetes, a total of 133 strains were isolated from Saharan soil samples of seven Algerian regions by dilution technique on chitin-vitamins agar medium. Screening for antagonistic properties using streak assay method showed that 25% of isolates demonstrated strong activities against a wide range of plant pathogenic fungi. Due to their strong anti-Fusarium activities, six of these isolates were selected and subsequently related to Streptomyces species by polyphasic analysis. These isolates were evaluated for their biocontrol ability against Fusarium culmorum, a serious pathogenic fungus of cereals crops related to damping-off and seedling blight resulting in yield loss. Barley seeds were chosen as cereal plant model. Surface bacterized seeds with TW3, RI3 and TW2 strains expressed the highest performances and permit to reduce significantly both the disease occurrence on seedlings (62-76%) and the extent of seedling blight symptoms (over than 95%). However, a negative effect on plant establishment was observed for RI3 treatment. The genus Fusarium is considered to be one of the most problematic phytopathogenic fungi for crop culture worldwide. Inside this genus, F. culmorum is the aetiological agent of seedling blight in various monocotyledonous plants such as barley and cause extensive yield and quality losses in humid and semi-humid regions. Biological control may be a successful alternative to chemical control, particularly with the controversy surrounding the use of the fungicides and the limited obtained results to control F. culmorum. This study highlights the effectiveness of some antagonistic Streptomyces isolated from Algerian Saharan soils to control F. culmorum by the reduction in disease occurrence and disease severity suggesting their use on microbial biocontrol formulation against soilborne diseases. © 2012 The Society for Applied Microbiology.

Induction of DIMBOA accumulation and systemic defense responses as a mechanism of enhanced resistance of mycorrhizal corn (Zea mays L.) to sheath blight.

PubMed

Song, Yuan Yuan; Cao, Man; Xie, Li Jun; Liang, Xiao Ting; Zeng, Ren Sen; Su, Yi Juan; Huang, Jing Hua; Wang, Rui Long; Luo, Shi Ming

2011-11-01

Arbuscular mycorrhizas are the most important symbioses in terrestrial ecosystems and they enhance the plant defense against numerous soil-borne pathogenic fungi and nematodes. Two corn (Zea mays) varieties, Gaoyou-115 that is susceptible to sheath blight disease caused by Rhizoctonia solani and Yuenong-9 that is resistant, were used for mycorrhizal inoculation in this study. Pre-inoculation of susceptible Gaoyou-115 with arbuscular mycorrhizal fungus (AMF) Glomus mosseae significantly reduced the disease incidence and disease severity of sheath blight of corn. HPLC analysis showed that AMF inoculation led to significant increase in 2,4-dihydroxy-7-methoxy-2 H-1,4-benzoxazin-3(4 H)-one (DIMBOA) accumulation in the roots of both corn varieties and in leaves of resistant Yuenong-9. R. solani inoculation alone did not result in accumulation of DIMBOA in both roots and leaves of the two corn varieties. Our previous study showed that DIMBOA strongly inhibited mycelial growth of R. solani in vitro. Real-time PCR analysis showed that mycorrhizal inoculation itself did not affect the transcripts of most genes tested. However, pre-inoculation with G. mosseae induced strong responses of three defense-related genes PR2a, PAL, and AOS, as well as BX9, one of the key genes in DIMBOA biosynthesis pathway, in the leaves of corn plants of both Yuenong-9 and Gaoyou-115 after the pathogen attack. Induction of defense responses in pre-inoculated plants was much higher and quicker than that in non-inoculated plants upon R. solani infection. These results indicate that induction of accumulation of DIMBOA, an important phytoalexin in corn, and systemic defense responses by AMF, plays a vital role in enhanced disease resistance of mycorrhizal plants of corn against sheath blight. This study also suggests that priming is an important mechanism in mycorrhiza-induced resistance.

Understanding the recent colonization history of a plant pathogenic fungus using population genetic tools and Approximate Bayesian Computation

PubMed Central

Barrès, B; Carlier, J; Seguin, M; Fenouillet, C; Cilas, C; Ravigné, V

2012-01-01

Understanding the processes by which new diseases are introduced in previously healthy areas is of major interest in elaborating prevention and management policies, as well as in understanding the dynamics of pathogen diversity at large spatial scale. In this study, we aimed to decipher the dispersal processes that have led to the emergence of the plant pathogenic fungus Microcyclus ulei, which is responsible for the South American Leaf Blight (SALB). This fungus has devastated rubber tree plantations across Latin America since the beginning of the twentieth century. As only imprecise historical information is available, the study of population evolutionary history based on population genetics appeared most appropriate. The distribution of genetic diversity in a continental sampling of four countries (Brazil, Ecuador, Guatemala and French Guiana) was studied using a set of 16 microsatellite markers developed specifically for this purpose. A very strong genetic structure was found (Fst=0.70), demonstrating that there has been no regular gene flow between Latin American M. ulei populations. Strong bottlenecks probably occurred at the foundation of each population. The most likely scenario of colonization identified by the Approximate Bayesian Computation (ABC) method implemented in 𝒟ℐ𝒴𝒜ℬ𝒞 suggested two independent sources from the Amazonian endemic area. The Brazilian, Ecuadorian and Guatemalan populations might stem from serial introductions through human-mediated movement of infected plant material from an unsampled source population, whereas the French Guiana population seems to have arisen from an independent colonization event through spore dispersal. PMID:22828899

Inferring Roles in Defense from Metabolic Allocation of Rice Diterpenoids.

PubMed

Lu, Xuan; Zhang, Juan; Brown, Benjamin; Li, Riqing; Rodríguez-Romero, Julio; Berasategui, Aileen; Liu, Bo; Xu, Meimei; Luo, Dangping; Pan, Zhiqiang; Baerson, Scott; Gershenzon, Jonathan; Li, Zhaohu; Sesma, Ane; Yang, Bing; Peters, Reuben J

2018-04-24

Among their responses to microbial infection, plants deploy an arsenal of natural antibiotic products. These historically have been identified on the basis of their antibiotic activity in vitro, which leaves open the question of their relevance to defense in planta. The vast majority of such natural products from the important crop plant rice (Oryza sativa) are diterpenoids whose biosynthesis proceeds via either ent- or syn- copalyl diphosphate (CPP) intermediates, and which were isolated on the basis of their antibiotic activity against the fungal blast pathogen Magnaporthe oryzae. However, rice plants in which the gene for the syn-CPP synthase Os-CPS4 is knocked-out do not exhibit increased susceptibility to M. oryzae. Here we show that knocking-out or knocking-down Os-CPS4 actually decreases susceptibility to the bacterial leaf blight pathogen Xanthomonas oryzae. By contrast, genetic manipulation of the gene for the ent-CPP synthase Os-CPS2 alters susceptibility to both M. oryzae and X. oryzae. Despite the secretion of diterpenoids dependent on Os-CPS2 or Os-CPS4 from roots, neither knock-out exhibited significant changes in the composition of their rhizosphere bacterial communities. Nevertheless, rice plants allocate substantial metabolic resources towards syn- and ent-CPP derived diterpenoids upon infection/induction. Further investigation revealed that Os-CPS4 plays a role in fungal non-host disease resistance. Thus, examination of metabolic allocation provides important clues into physiological function. © 2018 American Society of Plant Biologists. All rights reserved.

Impact of Austropuccinia psidii (myrtle rust) on Myrtaceae-rich wet sclerophyll forests in south east Queensland.

PubMed

Pegg, Geoff; Taylor, Tamara; Entwistle, Peter; Guymer, Gordon; Giblin, Fiona; Carnegie, Angus

2017-01-01

In April 2010, Austropuccinia psidii (formerly Puccinia psidii) was detected for the first time in Australia on the central coast of New South Wales. The fungus spread rapidly along the east coast and can now be found infecting vegetation in a range of native forest ecosystems with disease impacts ranging from minor leaf spots to severe shoot and stem blight and tree dieback. Localised extinction of some plant species has been recorded. In 2014, the impact of A. psidii was observed for the first time in a wet sclerophyll site with a rainforest understory, dominated by species of Myrtaceae, in Tallebudgera Valley, south east Queensland, Australia. This study aimed to determine the impact of A. psidii on individual species and species composition. Here we provide quantitative and qualitative evidence on the significant impact A. psidii has in native ecosystems, on a broader range of species than previously reported. Archirhodomyrtus beckleri, Decaspermum humile, Gossia hillii and Rhodamnia maideniana are in serious decline, with significant increases in tree mortality over the period of our study. This research further highlights the potential of this invasive pathogen to negatively impact native ecosystems and biodiversity.

Impact of Austropuccinia psidii (myrtle rust) on Myrtaceae-rich wet sclerophyll forests in south east Queensland

PubMed Central

Taylor, Tamara; Entwistle, Peter; Guymer, Gordon; Giblin, Fiona; Carnegie, Angus

2017-01-01

In April 2010, Austropuccinia psidii (formerly Puccinia psidii) was detected for the first time in Australia on the central coast of New South Wales. The fungus spread rapidly along the east coast and can now be found infecting vegetation in a range of native forest ecosystems with disease impacts ranging from minor leaf spots to severe shoot and stem blight and tree dieback. Localised extinction of some plant species has been recorded. In 2014, the impact of A. psidii was observed for the first time in a wet sclerophyll site with a rainforest understory, dominated by species of Myrtaceae, in Tallebudgera Valley, south east Queensland, Australia. This study aimed to determine the impact of A. psidii on individual species and species composition. Here we provide quantitative and qualitative evidence on the significant impact A. psidii has in native ecosystems, on a broader range of species than previously reported. Archirhodomyrtus beckleri, Decaspermum humile, Gossia hillii and Rhodamnia maideniana are in serious decline, with significant increases in tree mortality over the period of our study. This research further highlights the potential of this invasive pathogen to negatively impact native ecosystems and biodiversity. PMID:29161305

New species, hyper-diversity and potential importance of Calonectria spp. from Eucalyptus in South China

PubMed Central

Lombard, L.; Chen, S.F.; Mou, X.; Zhou, X.D.; Crous, P.W.; Wingfield, M.J.

2015-01-01

Plantation forestry is expanding rapidly in China to meet an increasing demand for wood and pulp products globally. Fungal pathogens including species of Calonectria represent a serious threat to the growth and sustainability of this industry. Surveys were conducted in the Guangdong, Guangxi and Hainan Provinces of South China, where Eucalyptus trees in plantations or cuttings in nurseries displayed symptoms of leaf blight. Isolations from symptomatic leaves and soils collected close to infected trees resulted in a large collection of Calonectria isolates. These isolates were identified using the Consolidated Species Concept, employing morphological characters and DNA sequence comparisons for the β-tubulin, calmodulin, histone H3 and translation elongation factor 1-alpha gene regions. Twenty-one Calonectria species were identified of which 18 represented novel taxa. Of these, 12 novel taxa belonged to Sphaero-Naviculate Group and the remaining six to the Prolate Group. Southeast Asia appears to represent a centre of biodiversity for the Sphaero-Naviculate Group and this fact could be one of the important constraints to Eucalyptus forestry in China. The remarkable diversity of Calonectria species in a relatively small area of China and associated with a single tree species is surprising. PMID:26955194

A Xanthomonas oryzae pv. oryzae effector, XopR, associates with receptor-like cytoplasmic kinases and suppresses PAMP-triggered stomatal closure.

PubMed

Wang, Shuangfeng; Sun, Jianhang; Fan, Fenggui; Tan, Zhaoyun; Zou, Yanmin; Lu, Dongping

2016-09-01

Receptor-like kinases (RLKs) play important roles in plant immunity signaling; thus, many are hijacked by pathogen effectors to promote successful pathogenesis. Xanthomonas oryzae pv. oryzae (Xoo) is the causal agent of rice leaf blight disease. The strain PXO99A has 18 non-TAL (transcription activation-like) effectors; however, their mechanisms of action and host target proteins remain largely unknown. Although the effector XopR from the Xoo strain MAFF311018 was shown to suppress PAMP-triggered immune responses in Arabidopsis, its target has not yet been identified. Here, we show that PXO99A XopR interacts with BIK1 at the plasma membrane. BIK1 is a receptor-like cytoplasmic kinase (RLCK) belonging to the RLK family of proteins and mediates PAMP-triggered stomatal immunity. In turn, BIK1 phosphorylates XopR. Furthermore, XopR suppresses PAMP-triggered stomatal closure in transgenic Arabidopsis expressing XopR. In addition, XopR is able to associate with RLCKs other than BIK1. These results suggest that XopR likely suppresses plant immunity by targeting BIK1 and other RLCKs.

Gene expression profiling during asexual development of the late blight pathogen Phytophthora infestans reveals a highly dynamic transcriptome.

PubMed

Judelson, Howard S; Ah-Fong, Audrey M V; Aux, George; Avrova, Anna O; Bruce, Catherine; Cakir, Cahid; da Cunha, Luis; Grenville-Briggs, Laura; Latijnhouwers, Maita; Ligterink, Wilco; Meijer, Harold J G; Roberts, Samuel; Thurber, Carrie S; Whisson, Stephen C; Birch, Paul R J; Govers, Francine; Kamoun, Sophien; van West, Pieter; Windass, John

2008-04-01

Much of the pathogenic success of Phytophthora infestans, the potato and tomato late blight agent, relies on its ability to generate from mycelia large amounts of sporangia, which release zoospores that encyst and form infection structures. To better understand these stages, Affymetrix GeneChips based on 15,650 unigenes were designed and used to profile the life cycle. Approximately half of P. infestans genes were found to exhibit significant differential expression between developmental transitions, with approximately (1)/(10) being stage-specific and most changes occurring during zoosporogenesis. Quantitative reverse-transcription polymerase chain reaction assays confirmed the robustness of the array results and showed that similar patterns of differential expression were obtained regardless of whether hyphae were from laboratory media or infected tomato. Differentially expressed genes encode potential cellular regulators, especially protein kinases; metabolic enzymes such as those involved in glycolysis, gluconeogenesis, or the biosynthesis of amino acids or lipids; regulators of DNA synthesis; structural proteins, including predicted flagellar proteins; and pathogenicity factors, including cell-wall-degrading enzymes, RXLR effector proteins, and enzymes protecting against plant defense responses. Curiously, some stage-specific transcripts do not appear to encode functional proteins. These findings reveal many new aspects of oomycete biology, as well as potential targets for crop protection chemicals.

High levels of diversity and population structure in the potato late blight pathogen at the Mexico centre of origin.

PubMed

Wang, Jianan; Fernández-Pavía, Sylvia P; Larsen, Meredith M; Garay-Serrano, Edith; Gregorio-Cipriano, Rosario; Rodríguez-Alvarado, Gerardo; Grünwald, Niklaus J; Goss, Erica M

2017-02-01

Globally destructive crop pathogens often emerge by migrating out of their native ranges. These pathogens are often diverse at their centre of origin and may exhibit adaptive variation in the invaded range via multiple introductions from different source populations. However, source populations are generally unidentified or poorly studied compared to invasive populations. Phytophthora infestans, the causal agent of late blight, is one of the most costly pathogens of potato and tomato worldwide. Mexico is the centre of origin and diversity of P. infestans and migration events out of Mexico have enormously impacted disease dynamics in North America and Europe. The debate over the origin of the pathogen, and population studies of P. infestans in Mexico, has focused on the Toluca Valley, whereas neighbouring regions have been little studied. We examined the population structure of P. infestans across central Mexico, including samples from Michoacán, Tlaxcala and Toluca. We found high levels of diversity consistent with sexual reproduction in Michoacán and Tlaxcala and population subdivision that was strongly associated with geographic region. We determined that population structure in central Mexico has contributed to diversity in introduced populations based on relatedness of U.S. clonal lineages to Mexican isolates from different regions. Our results suggest that P. infestans exists as a metapopulation in central Mexico, and this population structure could be contributing to the repeated re-emergence of P. infestans in the United States and elsewhere. © 2016 John Wiley & Sons Ltd.

Validation of consensus quantitative trait loci associated with resistance to multiple foliar pathogens of maize.

PubMed

Asea, Godfrey; Vivek, Bindiganavile S; Bigirwa, George; Lipps, Patrick E; Pratt, Richard C

2009-05-01

Maize production in sub-Saharan Africa incurs serious losses to epiphytotics of foliar diseases. Quantitative trait loci conditioning partial resistance (rQTL) to infection by causal agents of gray leaf spot (GLS), northern corn leaf blight (NCLB), and maize streak have been reported. Our objectives were to identify simple-sequence repeat (SSR) molecular markers linked to consensus rQTL and one recently identified rQTL associated with GLS, and to determine their suitability as tools for selection of improved host resistance. We conducted evaluations of disease severity phenotypes in separate field nurseries, each containing 410 F2:3 families derived from a cross between maize inbred CML202 (NCLB and maize streak resistant) and VP31 (a GLS-resistant breeding line) that possess complimentary rQTL. F2:3 families were selected for resistance based on genotypic (SSR marker), phenotypic, or combined data and the selected F3:4 families were reevaluated. Phenotypic values associated with SSR markers for consensus rQTL in bins 4.08 for GLS, 5.04 for NCLB, and 1.04 for maize streak significantly reduced disease severity in both generations based on single-factor analysis of variance and marker-interval analysis. These results were consistent with the presence of homozygous resistant parent alleles, except in bin 8.06, where markers were contributed by the NCLB-susceptible parent. Only one marker associated with resistance could be confirmed in bins 2.09 (GLS) and 3.06 (NCLB), illustrating the need for more robust rQTL discovery, fine-mapping, and validation prior to undertaking marker-based selection.

Rooting response of azalea cultivars to hot water treatment used for pathogen conrol

USDA-ARS?s Scientific Manuscript database

Submerging terminal leafy cuttings of Rhododendron L. 'Gumpo White' ('Gumpo White' azalea) in 50 °C water for 21 min was previously shown to eliminate binucleate Rhizoctonia species, the cause of azalea web blight, from plant tissues. Prior to considering commercial use of this practice, a better un...

Examining the transcriptional response in wheat Fhb1 near-isogenic lines to Fusarium graminearum infection and deoxynivalenol treatment

USDA-ARS?s Scientific Manuscript database

Fusarium Head Blight (FHB) is a disease caused by the fungal pathogen Fusarium graminearum that affects wheat and other small grain cereals and can lead to severe yield loss and reduction in grain quality. Trichothecene mycotoxins, such as deoxynivalenol (DON), accumulate during infection and increa...

Potential of spreading binucleate Rhizoctonia from nursery propagation floors to trays containing azalea stem cuttings

USDA-ARS?s Scientific Manuscript database

Binucleate Rhizoctonia fungi cause web blight on azaleas and other woody ornamental plants. This research focused on one aspect of how the pathogen may spread from contaminated floors of propagation houses into trays containing clean azalea stem cuttings that generate new root systems. Rhizoctonia w...

Loop-mediated isothermal amplification for detection of the tomato and potato late blight pathogen, Phytophthora infestans

USDA-ARS?s Scientific Manuscript database

Aims: To design and validate a colorimetric loop-mediated isothermal amplification assay for rapid detection of P. infestans DNA. Methods and Results: Two sets of LAMP primers were designed and evaluated for their sensitivity and specificity for P. infestans. ITSII primers targeted a portion of the ...

Composition of the Fusarium graminearum species complex populations in wheat cropping environments in Southern Brazil

USDA-ARS?s Scientific Manuscript database

The Fusarium graminearum species complex (FGSC) comprises several toxigenic species that cause Fusarium head blight (FHB) in wheat. In this study, high number (n=671 isolates) of pathogenic isolates (isolated from infected spikes) was obtained from a 3-year large-scale survey (2009-2011) conducted o...

Reintroduction of American Chestnut in the National Forest System

Treesearch

Stacy L. Clark; Scott E. Schlarbaum; Cornelia C. Pinchot; Sandra L. Anagnostakis; Michael R. Saunders; Melissa Thomas-Van Gundy; Paul Schaberg; James McKenna; Jane F. Bard; Paul C. Berrang; David M. Casey; Chris E. Casey; Barbara Crane; Brian D. Jackson; Jeff D. Kochenderfer; Russ MacFarlane; Robert Makowske; Mark D. Miller; Jason A. Rodrigue; Jim Stelick; Christopher D. Thornton; Tyler S. Williamson

2014-01-01

American chestnut restoration depends on a multitude of biological, administrative, and technological factors. Germplasm traditionally bred for resistance to the chestnut blight disease caused by the exotic pathogen Cryphonectria parasitica has been deployed on national forests in the Eastern and Southern Regions of the National Forest System (NFS) since 2009. Trees...

Characterization and pathogenicity of Fusarium species associated with leaf spot of mango (Mangifera indica L.).

PubMed

Omar, Nurul Husna; Mohd, Masratulhawa; Mohamed Nor, Nik Mohd Izham; Zakaria, Latiffah

2018-01-01

Leaf spot diseases are mainly caused by fungi including Fusarium. In the present study several species of Fusarium were isolated from the leaf spot lesion of mango (Mangifera indica L.) Based on morphological characteristics, TEF-1α sequences and phylogenetic analysis, five species were identified as F. proliferatum, F. semitectum, F. mangiferae, F. solani and F. chlamydosporum. Pathogenicity test indicated that representative isolates of F. proliferatum, F. semitectum and F. chlamydosporum were pathogenic on mango leaves causing leaf spot with low to moderate virulence. Nevertheless, abundance of spots on the leaf can disrupt photosynthesis which in turn reduced growth, and lead to susceptibility to infection by opportunistic pathogens due to weakening of the plant. Fusarium solani and F. mangiferae were non-pathogenic and it is possible that both species are saprophyte which associated with nutrient availability on the surface of the leaf through decaying leave tissues. The occurrence of Fusarium spp. on the leaf spot lesion and the effect from the disease needs to be considered when developing disease management method of mango cultivation as numerous spot on the leaves could effect the photosynthesis process and finally giving low yield and less quality of mango. Copyright © 2017. Published by Elsevier Ltd.

Comparative genome analysis of rice-pathogenic Burkholderia provides insight into capacity to adapt to different environments and hosts.

PubMed

Seo, Young-Su; Lim, Jae Yun; Park, Jungwook; Kim, Sunyoung; Lee, Hyun-Hee; Cheong, Hoon; Kim, Sang-Mok; Moon, Jae Sun; Hwang, Ingyu

2015-05-06

In addition to human and animal diseases, bacteria of the genus Burkholderia can cause plant diseases. The representative species of rice-pathogenic Burkholderia are Burkholderia glumae, B. gladioli, and B. plantarii, which primarily cause grain rot, sheath rot, and seedling blight, respectively, resulting in severe reductions in rice production. Though Burkholderia rice pathogens cause problems in rice-growing countries, comprehensive studies of these rice-pathogenic species aiming to control Burkholderia-mediated diseases are only in the early stages. We first sequenced the complete genome of B. plantarii ATCC 43733T. Second, we conducted comparative analysis of the newly sequenced B. plantarii ATCC 43733T genome with eleven complete or draft genomes of B. glumae and B. gladioli strains. Furthermore, we compared the genome of three rice Burkholderia pathogens with those of other Burkholderia species such as those found in environmental habitats and those known as animal/human pathogens. These B. glumae, B. gladioli, and B. plantarii strains have unique genes involved in toxoflavin or tropolone toxin production and the clustered regularly interspaced short palindromic repeats (CRISPR)-mediated bacterial immune system. Although the genome of B. plantarii ATCC 43733T has many common features with those of B. glumae and B. gladioli, this B. plantarii strain has several unique features, including quorum sensing and CRISPR/CRISPR-associated protein (Cas) systems. The complete genome sequence of B. plantarii ATCC 43733T and publicly available genomes of B. glumae BGR1 and B. gladioli BSR3 enabled comprehensive comparative genome analyses among three rice-pathogenic Burkholderia species responsible for tissue rotting and seedling blight. Our results suggest that B. glumae has evolved rapidly, or has undergone rapid genome rearrangements or deletions, in response to the hosts. It also, clarifies the unique features of rice pathogenic Burkholderia species relative to other animal and human Burkholderia species.

Fusarium praegraminearum sp. nov. is a novel nivalenol mycotoxin-producing pathogen from New Zealand can induce head blight on wheat

USDA-ARS?s Scientific Manuscript database

We report on the molecular and morphological characterization of a novel B-type trichothecene toxin-producing species (i.e., B clade) recovered from litter in a maize field near Wellington, New Zealand, which is described as Fusarium praegraminearum sp. nov. This species was initially identified as ...

Evaluation of chemical and biological agents for control of Phytophthora species on intact plants or detached leaves of rhododendron and lilac

Treesearch

R.G. Linderman; E.A. Davis

2006-01-01

The recent incidence of Ramorum blight, caused by Phytophthora ramorum, on many nursery crops has focused attention on improving management strategies against Phytophthora diseases in nurseries. We evaluated several chemical agents that target Oomycete pathogens for their capacity to inhibit infection of rhododendron or lilac...

Plasmid Content of Isolates of Erwinia amylovora from Orchards in Washington and Oregon in the USA

USDA-ARS?s Scientific Manuscript database

Washington (WA) and Oregon (OR) represent a major pome fruit production region of the United States, and streptomycin-resistant isolates of the fire blight pathogen Erwinia amylovora are common in orchards in this region. We examined the plasmid content of a collection of more than 200 isolates of ...

A North American isolate of Fusarium graminearum: toxicity and biosynthesis of a new type A trichothecene

USDA-ARS?s Scientific Manuscript database

Fusarium graminearum is one of the economically most important plant pathogens causing diseases such as Fusarium Head Blight (FHB) of small grain cereals and ear rot of maize. The mycotoxin deoxynivalenol (DON) produced by F. graminearum is a virulence factor in wheat and probably also on other host...

Standardizing the Nomenclature for Clonal Lineages of the Sudden Oak Death Pathogen, Phytophthora ramorum

USDA-ARS?s Scientific Manuscript database

Phytophthora ramorum, the causal agent of sudden oak death and ramorum blight, is known to exist as three distinct clonal lineages based on a range of molecular marker systems. However, in the recent literature there exists no consensus on naming of lineages. Here we name clonal lineages of P. ramor...

Effects of Phytophthora ramorum on volatile organic compound emissions of Rhododendron using gas chromatography-mass spectrometry

USDA-ARS?s Scientific Manuscript database

Phytophthora ramorum is an invasive and devastating plant pathogen that causes sudden oak death in coastal forests in the western United States and ramorum blight in nursery ornamentals and native plants in various landscapes. As a broad host-range quarantine pest that can be asymptomatic in some ho...

Rhododendron maximum impacts seed bank composition and richness following Tsuga canadensis loss in riparian forests

Treesearch

Tristan M. Cofer; Katherine J. Elliott; Janis K. Bush; Chelcy F. Miniat

2018-01-01

Southern Appalachian riparian forests have undergone changes in composition and function from invasive pathogens and pests. Castanea dentata mortality in the 1930s from chestnut blight (Cryphonectria parasitica) and Tsuga canadensis mortality in the 2000s from the hemlock woolly adelgid (Adelges tsugae) have led to the expansion and...

REDUCING FUNGICIDE USAGE FOR POTATO PRODUCTION BY UNRAVELING TUBER AND FOLIAGE DEFENSE MECHANISMS AGAINST THE LATE BLIGHT PATHOGEN PHYTOPHTHORA INFESTANS

EPA Science Inventory

1. More than 215 million RNA sequences from potato tubers infected with P. infestans were generated. This represents a >1,300-fold increase in data generation relative to our previous expectation of 160,000 sequence reads. This increase was achieved by capi...

2. Phytosanitation: A systematic approach to disease prevention

   Treesearch

   Thomas D. Landis

   2013-01-01

   Phytosanitation is not a new concept but has received renewed attention due to the increasing threat of nursery spread Phytophthora ramorum (PRAM), the fungus-like pathogen that causes Sudden Oak Death. This disease has the potental to become the most serious forest pest since white pine blister rust and chestnut blight. Phytosanitation can help prevent the spread of...

3. Molecules that inhibit growth of Fusarium graminearum, a pathogen causing disease in wheat and corn

   USDA-ARS?s Scientific Manuscript database

   Fusarium graminearum can cause head blight in wheat and stalk or ear rot in corn, which results in crop losses. Discovery of novel antifungal resistance proteins are crucial to mitigating crop losses. We found, via in vitro studies, a small cationic peptide was capable of inhibiting the growth of th...

4. Species diversity and toxigenic potential of Fusarium graminearum complex isolates from maize fields in northwest Argentina

   USDA-ARS?s Scientific Manuscript database

   Members of the Fusarium graminearum species complex (Fg complex) are the causal agents of ear rot in maize and Fusarium head blight of wheat and other small grain cereals. The potential of these pathogens to contaminate cereals with trichothecene mycotoxins is a health risk for both humans and anima...

5. WAX INDUCER1 (HvWIN1) transcription factor regulates free fatty acid biosynthetic genes to reinforce cuticle to resist Fusarium head blight in barley spikelets

   PubMed Central

   Kumar, Arun; Yogendra, Kalenahalli N.; Karre, Shailesh; Kushalappa, Ajjamada C.; Dion, Yves; Choo, Thin M.

   2016-01-01

   Fusarium head blight (FHB), caused by Fusarium graminearum, is one of the most devastating diseases of wheat and barley. Resistance to FHB is highly complex and quantitative in nature, and is most often classified as resistance to spikelet infection and resistance to spread of pathogen through the rachis. In the present study, a resistant (CI9831) and a susceptible (H106-371) two-row barley genotypes, with contrasting levels of spikelet resistance to FHB, pathogen or mock-inoculated, were profiled for metabolites based on liquid chromatography and high resolution mass spectrometry. The key resistance-related (RR) metabolites belonging to fatty acids, phenylpropanoids, flavonoids and terpenoid biosynthetic pathways were identified. The free fatty acids (FFAs) linoleic and palmitic acids were among the highest fold change RR induced (RRI) metabolites. These FFAs are deposited as cutin monomers and oligomers to reinforce the cuticle, which acts as a barrier to pathogen entry. Quantitative real-time PCR studies revealed higher expressions of KAS2, CYP86A2, CYP89A2, LACS2 and WAX INDUCER1 (HvWIN1) transcription factor in the pathogen-inoculated resistant genotype than in the susceptible genotype. Knockdown of HvWIN1 by virus-induced genes silencing (VIGS) in resistant genotype upon pathogen inoculation increased the disease severity and fungal biomass, and decreased the abundance of FFAs like linoleic and palmitic acids. Notably, the expression of CYP86A2, CYP89A2 and LAC2 genes was also suppressed, proving the link of HvWIN1 in regulating these genes in cuticle biosynthesis as a defense response. PMID:27194736

6. Sharing a Host Plant (Wheat [Triticum aestivum]) Increases the Fitness of Fusarium graminearum and the Severity of Fusarium Head Blight but Reduces the Fitness of Grain Aphids (Sitobion avenae)

   PubMed Central

   Drakulic, Jassy; Caulfield, John; Woodcock, Christine; Jones, Stephen P. T.; Linforth, Robert; Bruce, Toby J. A.

   2015-01-01

   We hypothesized that interactions between fusarium head blight-causing pathogens and herbivores are likely to occur because they share wheat as a host plant. Our aim was to investigate the interactions between the grain aphid, Sitobion avenae, and Fusarium graminearum on wheat ears and the role that host volatile chemicals play in mediating interactions. Wheat ears were treated with aphids and F. graminearum inoculum, together or separately, and disease progress was monitored by visual assessment and by quantification of pathogen DNA and mycotoxins. Plants exposed to both aphids and F. graminearum inoculum showed accelerated disease progression, with a 2-fold increase in disease severity and 5-fold increase in mycotoxin accumulation over those of plants treated only with F. graminearum. Furthermore, the longer the period of aphid colonization of the host prior to inoculation with F. graminearum, the greater the amount of pathogen DNA that accumulated. Headspace samples of plant volatiles were collected for use in aphid olfactometer assays and were analyzed by gas chromatography-mass spectrometry (GC-MS) and GC-coupled electroantennography. Disease-induced plant volatiles were repellent to aphids, and 2-pentadecanone was the key semiochemical underpinning the repellent effect. We measured aphid survival and fecundity on infected wheat ears and found that both were markedly reduced on infected ears. Thus, interactions between F. graminearum and grain aphids on wheat ears benefit the pathogen at the expense of the pest. Our findings have important consequences for disease epidemiology, because we show increased spread and development of host disease, together with greater disease severity and greater accumulation of pathogen DNA and mycotoxin, when aphids are present. PMID:25769834

7. Sharing a Host Plant (Wheat [Triticum aestivum]) Increases the Fitness of Fusarium graminearum and the Severity of Fusarium Head Blight but Reduces the Fitness of Grain Aphids (Sitobion avenae).

   PubMed

   Drakulic, Jassy; Caulfield, John; Woodcock, Christine; Jones, Stephen P T; Linforth, Robert; Bruce, Toby J A; Ray, Rumiana V

   2015-05-15

   We hypothesized that interactions between fusarium head blight-causing pathogens and herbivores are likely to occur because they share wheat as a host plant. Our aim was to investigate the interactions between the grain aphid, Sitobion avenae, and Fusarium graminearum on wheat ears and the role that host volatile chemicals play in mediating interactions. Wheat ears were treated with aphids and F. graminearum inoculum, together or separately, and disease progress was monitored by visual assessment and by quantification of pathogen DNA and mycotoxins. Plants exposed to both aphids and F. graminearum inoculum showed accelerated disease progression, with a 2-fold increase in disease severity and 5-fold increase in mycotoxin accumulation over those of plants treated only with F. graminearum. Furthermore, the longer the period of aphid colonization of the host prior to inoculation with F. graminearum, the greater the amount of pathogen DNA that accumulated. Headspace samples of plant volatiles were collected for use in aphid olfactometer assays and were analyzed by gas chromatography-mass spectrometry (GC-MS) and GC-coupled electroantennography. Disease-induced plant volatiles were repellent to aphids, and 2-pentadecanone was the key semiochemical underpinning the repellent effect. We measured aphid survival and fecundity on infected wheat ears and found that both were markedly reduced on infected ears. Thus, interactions between F. graminearum and grain aphids on wheat ears benefit the pathogen at the expense of the pest. Our findings have important consequences for disease epidemiology, because we show increased spread and development of host disease, together with greater disease severity and greater accumulation of pathogen DNA and mycotoxin, when aphids are present. Copyright © 2015, American Society for Microbiology. All Rights Reserved.

8. Regional differences in the composition of Fusarium Head Blight pathogens and mycotoxins associated with wheat in Mexico.

   PubMed

   Cerón-Bustamante, Minely; Ward, Todd J; Kelly, Amy; Vaughan, Martha M; McCormick, Susan P; Cowger, Christina; Leyva-Mir, Santos G; Villaseñor-Mir, Héctor E; Ayala-Escobar, Victoria; Nava-Díaz, Cristian

   2018-05-20

   Fusarium Head Blight (FHB) is a destructive disease of small grain cereals and a major food safety concern. Epidemics result in substantial yield losses, reduction in crop quality, and contamination of grains with trichothecenes and other mycotoxins. A number of different fusaria can cause FHB, and there are significant regional differences in the occurrence and prevalence of FHB pathogen species and their associated mycotoxins. Information on FHB pathogen and mycotoxin diversity in Mexico has been extremely limited, but is needed to improve disease and mycotoxin control efforts. To address this, we used a combination of DNA sequence-based methods and in-vitro toxin analyses to characterize FHB isolates collected from symptomatic wheat in Mexico during the 2013 and 2014 growing seasons. Among 116 Fusarium isolates, we identified five species complexes including nine named Fusarium species and 30 isolates representing unnamed or potentially novel species. Significant regional differences (P < 0.001) in pathogen composition were observed, with F. boothii accounting for >90% of isolates from the Mixteca region in southern Mexico, whereas F. avenaceum and related members of the F. tricinctum species complex (FTSC) accounted for nearly 75% of isolates from the Highlands region in Central Mexico. F. graminearum, which is the dominant FHB pathogen in other parts of North America, was not present among the isolates from Mexico. F. boothii isolates had the 15-acetyldeoxynivalenol toxin type, and some of the minor FHB species produced trichothecenes, such as nivalenol, T-2 toxin and diacetoxyscirpenol. None of the FTSC isolates tested was able to produce trichothecenes, but many produced chlamydosporol and enniatin B. Published by Elsevier B.V.

9. Exploring new roles for the rpoS gene in the survival and virulence of the fire blight pathogen Erwinia amylovora.

   PubMed

   Santander, Ricardo D; Monte-Serrano, Mercedes; Rodríguez-Herva, José J; López-Solanilla, Emilia; Rodríguez-Palenzuela, Pablo; Biosca, Elena G

   2014-12-01

   Erwinia amylovora causes fire blight in economically important plants of the family Rosaceae. This bacterial pathogen spends part of its life cycle coping with starvation and other fluctuating environmental conditions. In many Gram-negative bacteria, starvation and other stress responses are regulated by the sigma factor RpoS. We obtained an E. amylovora rpoS mutant to explore the role of this gene in starvation responses and its potential implication in other processes not yet studied in this pathogen. Results showed that E. amylovora needs rpoS to develop normal starvation survival and viable but nonculturable (VBNC) responses. Furthermore, this gene contributed to stationary phase cross-protection against oxidative, osmotic, and acid stresses and was essential for cross-protection against heat shock, but nonessential against acid shock. RpoS also mediated regulation of motility, exopolysaccharide synthesis, and virulence in immature loquats, but not in pear plantlets, and contributed to E. amylovora survival in nonhost tissues during incompatible interactions. Our results reveal some unique roles for the rpoS gene in E. amylovora and provide new knowledge on the regulation of different processes related to its ecology, including survival in different environments and virulence in immature fruits. © 2014 Federation of European Microbiological Societies. Published by John Wiley & Sons Ltd. All rights reserved.

10. A Novel Botrytis Species Is Associated with a Newly Emergent Foliar Disease in Cultivated Hemerocallis

    PubMed Central

    Grant-Downton, Robert T.; Terhem, Razak B.; Kapralov, Maxim V.; Mehdi, Saher; Rodriguez-Enriquez, M. Josefina; Gurr, Sarah J.; van Kan, Jan A. L.; Dewey, Frances M.

    2014-01-01

    Foliar tissue samples of cultivated daylilies (Hemerocallis hybrids) showing the symptoms of a newly emergent foliar disease known as ‘spring sickness’ were investigated for associated fungi. The cause(s) of this disease remain obscure. We isolated repeatedly a fungal species which proved to be member of the genus Botrytis, based on immunological tests. DNA sequence analysis of these isolates, using several different phyogenetically informative genes, indicated that they represent a new Botrytis species, most closely related to B. elliptica (lily blight, fire blight) which is a major pathogen of cultivated Lilium. The distinction of the isolates was confirmed by morphological analysis of asexual sporulating cultures. Pathogenicity tests on Hemerocallis tissues in vitro demonstrated that this new species was able to induce lesions and rapid tissue necrosis. Based on this data, we infer that this new species, described here as B. deweyae, is likely to be an important contributor to the development of ‘spring sickness’ symptoms. Pathogenesis may be promoted by developmental and environmental factors that favour assault by this necrotrophic pathogen. The emergence of this disease is suggested to have been triggered by breeding-related changes in cultivated hybrids, particularly the erosion of genetic diversity. Our investigation confirms that emergent plant diseases are important and deserve close monitoring, especially in intensively in-bred plants. PMID:24887415

11. Defense reactions of bean genotypes to bacterial pathogens in controlled conditions

    NASA Astrophysics Data System (ADS)

    Uysal, B.; Bastas, K. K.

    2018-03-01

    This study was focused on the role of antioxidant enzymes and total protein in imparting resistance against common bacterial blight caused by Xanthomonas axonopodis pv. phaseoli (Xap) and halo blight caused by Pseudomonas syringae pv. phaseolicola (Psp) in bean. Activities of Ascorbate peroxidase (APX), Catalase (CAT) and total protein were studied in resistant and susceptible bean genotypes. Five-day-old seedlings were inoculated with a bacterial suspension (108 CFU ml-1) and harvested at different time intervals (0, 12, 24 and 36 up to 72 h) under controlled growing conditions and assayed for antioxidant enzymes and total protein. Temporal increase of CAT, APX enzymes activities showed maximum activity at 12 h after both pathogens inoculation (hpi) in resistant cultivar, whereas in susceptible it increased at 72 h after both pathogens inoculation for CAT and 12, 24 h for APX enzymes. Maximum total protein activities were observed at 12 h and 24 h respectively after Xap, Psp inoculation (hpi) in resistant and maximum activities were observed at 24 h and 72 h respectively after Xap, Psp inoculation (hpi) in susceptible. Increase of antioxidant enzyme and total protein activities might be an important component in the defense strategy of resistance and susceptible bean genotypes against the bacterial infection. These findings suggest that disease protection is proportional to the amount of enhanced CAT, APX enzyme and total protein activity.

12. Five Reasons to Consider Phytophthora infestans a Reemerging Pathogen.

    PubMed

    Fry, W E; Birch, P R J; Judelson, H S; Grünwald, N J; Danies, G; Everts, K L; Gevens, A J; Gugino, B K; Johnson, D A; Johnson, S B; McGrath, M T; Myers, K L; Ristaino, J B; Roberts, P D; Secor, G; Smart, C D

    2015-07-01

    Phytophthora infestans has been a named pathogen for well over 150 years and yet it continues to "emerge", with thousands of articles published each year on it and the late blight disease that it causes. This review explores five attributes of this oomycete pathogen that maintain this constant attention. First, the historical tragedy associated with this disease (Irish potato famine) causes many people to be fascinated with the pathogen. Current technology now enables investigators to answer some questions of historical significance. Second, the devastation caused by the pathogen continues to appear in surprising new locations or with surprising new intensity. Third, populations of P. infestans worldwide are in flux, with changes that have major implications to disease management. Fourth, the genomics revolution has enabled investigators to make tremendous progress in terms of understanding the molecular biology (especially the pathogenicity) of P. infestans. Fifth, there remain many compelling unanswered questions.

Foliar pathogen and insect herbivore effects on two landslide tree species in Puerto Rico

Treesearch

Randall W. Myster

2002-01-01

To better understand pathogen/herbivore interactions and landslide regeneration, percent leaf area lost to disease and herbivory on two Puerto Rican trees over a 1-year period was sampled. Cecropia schreberiana saplings lost from 1 to 3% leaf area to pathogens and from 1 to 7% to herbivores. For Inga vera, both sapling and seedling losses to pathogens were minimal, but...

Fusarium culmorum: causal agent of foot and root rot and head blight on wheat.

PubMed

Scherm, Barbara; Balmas, Virgilio; Spanu, Francesca; Pani, Giovanna; Delogu, Giovanna; Pasquali, Matias; Migheli, Quirico

2013-05-01

Fusarium culmorum is a ubiquitous soil-borne fungus able to cause foot and root rot and Fusarium head blight on different small-grain cereals, in particular wheat and barley. It causes significant yield and quality losses and results in contamination of the grain with mycotoxins. This review summarizes recent research activities related to F. culmorum, including studies into its population diversity, mycotoxin biosynthesis, mechanisms of pathogenesis and resistance, the development of diagnostic tools and preliminary genome sequence surveys. We also propose potential research areas that may expand our basic understanding of the wheat-F. culmorum interaction and assist in the management of the disease caused by this pathogen. Fusarium culmorum (W.G. Smith) Sacc. Kingdom Fungi; Phylum Ascomycota; Subphylum Pezizomycotina; Class Sordariomycetes; Subclass Hypocreomycetidae; Order Hypocreales; Family Nectriaceae; Genus Fusarium. Foot and root rot (also known as Fusarium crown rot): seedling blight with death of the plant before or after emergence; brown discoloration on roots and coleoptiles of the infected seedlings; brown discoloration on subcrown internodes and on the first two/three internodes of the main stem; tiller abortion; formation of whiteheads with shrivelled white grains; Fusarium head blight: prematurely bleached spikelets or blighting of the entire head, which remains empty or contains shrunken dark kernels. IDENTIFICATION AND DETECTION: Morphological identification is based on the shape of the macroconidia formed on sporodochia on carnation leaf agar. The conidiophores are branched monophialides, short and wide. The macroconidia are relatively short and stout with an apical cell blunt or slightly papillate; the basal cell is foot-shaped or just notched. Macroconidia are thick-walled and curved, usually 3-5 septate, and mostly measuring 30-50 × 5.0-7.5 μm. Microconidia are absent. Oval to globose chlamydospores are formed, intercalary in the hyphae, solitary, in chains or in clumps; they are also formed from macroconidia. The colony grows very rapidly (1.6-2.2 cm/day) on potato dextrose agar (PDA) at the optimum temperature of 25 °C. The mycelium on PDA is floccose, whitish, light yellow or red. The pigment on the reverse plate on PDA varies from greyish-rose, carmine red or burgundy. A wide array of polymerase chain reaction (PCR) and real-time PCR tools, as well as complementary methods, which are summarised in the first two tables, have been developed for the detection and/or quantification of F. culmorum in culture and in naturally infected plant tissue. Fusarium culmorum has a wide range of host plants, mainly cereals, such as wheat, barley, oats, rye, corn, sorghum and various grasses. In addition, it has been isolated from sugar beet, flax, carnation, bean, pea, asparagus, red clover, hop, leeks, Norway spruce, strawberry and potato tuber. Fusarium culmorum has also been associated with dermatitis on marram grass planters in the Netherlands, although its role as a causal agent of skin lesions appears questionable. It is also isolated as a symbiont able to confer resistance to abiotic stress, and has been proposed as a potential biocontrol agent to control the aquatic weed Hydrilla spp. http://isolate.fusariumdb.org/; http://sppadbase.ipp.cnr.it/; http://www.broad.mit.edu/annotation/genome/fusarium_group/MultiHome.html; http://www.fgsc.net/Fusarium/fushome.htm; http://plantpath.psu.edu/facilities/fusarium-research-center; http://www.phi-base.org/; http://www.uniprot.org/; http://www.cabi.org/; http://www.indexfungorum.org/ © 2012 BSPP AND BLACKWELL PUBLISHING LTD.

Rapid identification of candidate genes for resistance to tomato late blight disease using next-generation sequencing technologies

PubMed Central

Arafa, Ramadan A.; Rakha, Mohamed T.; Kamel, Said M.

2017-01-01

Tomato late blight caused by Phytophthora infestans (Mont.) de Bary, also known as the Irish famine pathogen, is one of the most destructive plant diseases. Wild relatives of tomato possess useful resistance genes against this disease, and could therefore be used in breeding to improve cultivated varieties. In the genome of a wild relative of tomato, Solanum habrochaites accession LA1777, we identified a new quantitative trait locus for resistance against blight caused by an aggressive Egyptian isolate of P. infestans. Using double-digest restriction site–associated DNA sequencing (ddRAD-Seq) technology, we determined 6,514 genome-wide SNP genotypes of an F2 population derived from an interspecific cross. Subsequent association analysis of genotypes and phenotypes of the mapping population revealed that a 6.8 Mb genome region on chromosome 6 was a candidate locus for disease resistance. Whole-genome resequencing analysis revealed that 298 genes in this region potentially had functional differences between the parental lines. Among of them, two genes with missense mutations, Solyc06g071810.1 and Solyc06g083640.3, were considered to be potential candidates for disease resistance. SNP and SSR markers linking to this region can be used in marker-assisted selection in future breeding programs for late blight disease, including introgression of new genetic loci from wild species. In addition, the approach developed in this study provides a model for identification of other genes for attractive agronomical traits. PMID:29253902

Spatial Analysis of Phytophthora infestans Genotypes and Late Blight Severity on Tomato and Potato in the Del Fuerte Valley Using Geostatistics and Geographic Information Systems.

PubMed

Jaime-Garcia, R; Orum, T V; Felix-Gastelum, R; Trinidad-Correa, R; Vanetten, H D; Nelson, M R

2001-12-01

ABSTRACT Genetic structure of Phytophthora infestans, the causal agent of potato and tomato late blight, was analyzed spatially in a mixed potato and tomato production area in the Del Fuerte Valley, Sinaloa, Mexico. Isolates of P. infestans were characterized by mating type, allozyme analysis at the glucose-6-phosphate isomerase and peptidase loci, restriction fragment length polymorphism with probe RG57, metalaxyl sensitivity, and aggressiveness to tomato and potato. Spatial patterns of P. infestans genotypes were analyzed by geographical information systems and geo-statistics during the seasons of 1994-95, 1995-96, and 1996-97. Spatial analysis of the genetic structure of P. infestans indicates that geographic substructuring of this pathogen occurs in this area. Maps displaying the probabilities of occurrence of mating types and genotypes of P. infestans, and of disease severity at a regional scale, were presented. Some genotypes that exhibited differences in epidemiologically important features such as metalaxyl sensitivity and aggressiveness to tomato and potato had a restricted spread and were localized in isolated areas. Analysis of late blight severity showed recurring patterns, such as the earliest onset of the disease in the area where both potato and tomato were growing, strengthening the hypothesis that infected potato tubers are the main source of primary inoculum. The information that geostatistical analysis provides might help improve management programs for late blight in the Del Fuerte Valley.

Diplodia Tip Blight and Canker of Pines (Pest Alert)

Treesearch

USDA Forest Service

The fungus Diplodia pinea can cause serious damage to Austrian, ponderosa, red, Scots, mugo, jack, and white pine. Although it is considered a weak pathogen, it may successfully attack and kill trees. It may be more serious on trees growing out of their natural range or stressed by adverse climatic conditions or air pollution. Infection can occur as a result of hail...

HOPX1 Ea (Eop3) in Erwinia Amylovora functions as an avirulence gene in apple and is regulated by HRPL

USDA-ARS?s Scientific Manuscript database

Fire blight is a devastating disease of rosaceous plants caused by the Gram-negative bacterium E. amylovora. This pathogen delivers virulence proteins into host cells utilizing the Type-Three Secretion System (T3SS). Expression of the T3SS and associated substrates are activated by the alternative s...

Expression of ß-1,3-glucanase and ß-1,4-glucanase in two potato cultivars following challenge by the fungal pathogen Alternaria solani

USDA-ARS?s Scientific Manuscript database

Early blight of potato, caused by Alternaria solani, is a ubiquitous disease in many countries around the world. We have previously found that variation in resistance phenotypes exist between two different Iranian cultivars of potato. Cultivar ‘Diamond’ is more resistant to multiple isolates of A. s...

Variation in phenotype for resistance to Phytophthora ramorum in a range of species and cultivars of the genus Viburnum

Treesearch

Niklaus J. Grunwald; E. Anne Davis; Robert G. Linderman

2006-01-01

Phytophthora ramorum is a recently introduced plant pathogen causing a range of diseases including sudden oak death, Ramorum shoot dieback and Ramorum blight (Rizzo and others 2002, 2004; Werres and others 2001). P. ramorum also attacks several nursery crops including viburnum and rhododendron (Werres and others 2001). Since its...

Comparative Susceptibility of Plants Native to the Appalachian Range of the United States to Inoculation With Phytophthora ramorum

Treesearch

R.G. Linderman; Patricia B. de Sá; E.A. Davis

2008-01-01

Phytophthora ramorum, cause of sudden oak death of trees or ramorum blight of other plant species, has many hosts. Some geographic regions, such as the Appalachian range of the eastern United States, are considered high risk of becoming infested with the pathogen because known susceptible plants occur there and climatic characteristics appear...

Tuber resistance and slow rotting characteristics of potato clones associated with the Solanaceae Coordinated Agricultural Project to the US-24 clonal lineage of Phytophthora infestans

USDA-ARS?s Scientific Manuscript database

Late blight, caused by Phytophthora infestans, is a devastating disease on potato worldwide and new lineages of the pathogen continue to develop in the U.S. Breeding for resistance is important for economic and environmental purposes. The Solanaceae Coordinated Agricultural Project (SolCAP) focuses ...

Analysis of the Surface Properties of Wheat Spikelet Components and Their Role in Colonization by the Biocontrol Antagonist Cryptococcus flavescens OH 182.9

USDA-ARS?s Scientific Manuscript database

Cryptococcus flavescens OH 182.9 (NRRL Y-30216) is a biocontrol antagonist which has been shown to be effective in managing Fusarium head blight in wheat. Cryptococcus flavescens works by colonizing the wheat spikelet and competing with potential pathogens for the limited resources available. Know...

Regional and field-specific factors affect the composition of Fusarium head blight pathogens in subtropical no-till wheat agroecosystem of Brazil

USDA-ARS?s Scientific Manuscript database

A multiyear survey of >200 wheat fields in Paraná (PR) and Rio Grande do Sul (RS) states was conducted to assess the extent and distribution of Fusarium graminearum species complex (FGSC) diversity in the southern Brazilian wheat agroecosystem. Five species and three trichothecene genotypes were fou...

Migration patterns of the emerging plant pathogen Phytophthora ramorum on the West Coast of the United States of America

Treesearch

S. Prospero; N.J. Grünwald; L.M. Winton; E.M. Hansen

2009-01-01

Phytophthora ramorum (oomycetes) is the causal agent of sudden oak death and ramorum blight on trees, shrubs, and woody ornamentals in the forests of coastal California and southwestern Oregon and in nurseries of California, Oregon, and Washington. In this study, we investigated the genetic structure of P. ramorum on the West...

Genetic and genomic resources for mapping resistance to Phytophthora cinnamomi in chestnut

Treesearch

T. Zhebentyayeva; A. Chandra; A.G. Abbott; M.E. Staton; B.A. Olukolu; F.V. Hebard; L.L. Georgi; S.N. Jeffers; P.H. Sisco; J.B. James; C. Dana Nelson

2013-01-01

Root rot (caused by Phytophthora cinnamomi) and chestnut blight (caused by Cryphonectria parasitica) are the two most destructive diseases affecting American chestnut, Castanea dentata. Therefore, breeding for resistance to both pathogens simultaneously is essential before the American chestnut can be restored to its full native range. Using combined genetic and...

Potential of Microbispora sp. V2 as biocontrol agent against Sclerotium rolfsii, the causative agent of southern blight of Zea mays L (Baby corn)--in vitro studies.

PubMed

Patil, N N; Waghmode, M S; Gaikwad, P S; Gajbhiye, M H; Gunjal, A B; Nawani, N N; Kapadnis, B P

2014-11-01

The study was undertaken with the aim of exploring novel and beneficial agro activities of rare actinomycetes like Microbispora sp. V2. The antagonistic activity of Microbispora sp. V2 was evaluated as a biocontrol agents against Sclerotium rolfsii, a soil-borne fungal plant pathogen. The methodology performed for evaluation of biocontrol agent was in vitro evaluation assay which comprised of three tests viz., cellophane overlay technique, seed germination test and Thiram (fungicide) tolerance of Microbispora sp. V2. The isolate was found to inhibit the fungal pathogen Sclerotium rolfsii to 91.43% in cellophane assay. In seed germination assay, Microbispora sp. V2 treated seeds resulted in 25.75% increased germination efficiency, as compared to seeds infected by Sclerotium rolfsii. The isolate Microbispora sp. V2 could tolerate 1000 microg mL(-1) of Thiram (fungicide). The in vitro assay studies proved that Microbispora sp. V2 can be used as antifungal antagonist and thus posses' great potential as biocontrol agent against southern blight caused by Sclerotium rolfsii in Zea mays L (Baby corn) which causes large economical losses.

Changing Pattern of Crop Fraction in Late Blight Induced Potato Crops in Potato Bowl of West Bengal by using Multi-temporal Time Series AWiFs Data

NASA Astrophysics Data System (ADS)

Chakrabarty, Abhisek

2016-07-01

Crop fraction is the ratio of crop occupying a unit area in ground pixel, is very important for monitoring crop growth. One of the most important variables in crop growth monitoring is the fraction of available solar radiation intercepted by foliage. Late blight of potato (Solanum tuberosum), caused by the oomycete pathogen Phytophthora infestans, is considered to be the most destructive crop diseases of potato worldwide. Under favourable climatic conditions, and without intervention (i.e. fungicide sprays), the disease can destroy potato crop within few weeks. Therefore it is important to evaluate the crop fraction for monitoring the healthy and late blight affected potato crops. This study was conducted in potato bowl of West Bengal, which consists of districts of Hooghly, Howrah, Burdwan, Bankuara, and Paschim Medinipur. In this study different crop fraction estimation method like linear spectral un-mixing, Normalized difference vegetation index (NDVI) based DPM model (Zhang et al. 2013), Ratio vegetation index based DPM model, improved Pixel Dichotomy Model (Li et al. 2014) ware evaluated using multi-temporal IRS AWiFs data in two successive potato growing season of 2012-13 and 2013-14 over the study area and compared with measured crop fraction. The comparative study based on measured healthy and late blight affected potato crop fraction showed that improved Pixel Dichotomy Model maintain the high coefficient of determination (R2= 0.835) with low root mean square error (RMSE=0.21) whereas the correlation values of NDVI based DPM model and RVI based DPM model is 0.763 and 0.694 respectively. The changing pattern of crop fraction profile of late blight affected potato crop was studied in respect of healthy potato crop fraction which was extracted from the 269 GPS points of potato field. It showed that the healthy potato crop fraction profile maintained the normal phenological trend whereas the late blight affected potato crop fraction profile suddenly fallen after late blight disease affected in potato crops. Therefore, it can be concluded that based on the result of this study the improved Pixel Dichotomy Model is the most convenient method for crop fraction estimation for this region with satisfactory accuracy.

Fusarium agapanthi sp. nov, a novel bikaverin and fusarubin-producing leaf and stem spot pathogen of Agapanthus praecox (African lily) from Australia and Italy

USDA-ARS?s Scientific Manuscript database

This study was conducted to characterize a novel Fusarium species that caused leaf and stem spot on Agapanthus praecox (Agapanthus, African lily) in northern Italy and leaf rot and spot on the same host in Melbourne, Australia. Formally described as Fusarium agapanthi, this pathogen was analyzed usi...

Differentiation of Corynespora cassiicola and Cercospora sp. in leaf-spot diseases of Hydrangea macrophylla using a PCR-mediated method

Treesearch

M. T. Mmbaga; L. Mackasmiel; Ned Klopfenstein

2015-01-01

Corynespora cassiicola and Cercospora sp. have been identified as the most prevalent and destructive leaf-spot pathogens of garden hydrangea [Hydrangea macrophylla (Thunberg) Seringe] in the southeastern USA, but they are often difficult to accurately detect and distinguish because they often occur together in a disease complex with other pathogenic leaf-spot...

The in planta proteome of wild type strains of the fire blight pathogen, Erwinia amylovora.

PubMed

Holtappels, M; Vrancken, K; Noben, J P; Remans, T; Schoofs, H; Deckers, T; Valcke, R

2016-04-29

Erwinia amylovora is a Gram-negative plant pathogen that causes fire blight. This disease affects most members of the Rosaceae family including apple and pear. Here, an infection model is introduced to study proteomic changes in a highly virulent E. amylovora strain upon interaction with its host as compared to a lower virulent strain. For this purpose separate shoots of apple rootstocks were wound-infected and when infection became systemic, bacterial cells were isolated and processed for analysis in a proteomics platform combining 2-D fluorescence difference gel electrophoresis and mass spectrometry. Comparing the proteome of the isolates, significant abundance changes were observed in proteins involved in sorbitol metabolism, amylovoran production as well as in protection against plant defense mechanisms. Furthermore several proteins associated with virulence were more abundant in the higher virulent strain. Changes at the proteome level showed good accordance at the transcript level, as was verified by RT-qPCR. In conclusion, this infection model may be a valuable tool to unravel the complexity of plant-pathogen interactions and to gain insight in the molecular mechanisms associated with virulence of E. amylovora, paving the way for the development of plant-protective interventions against this detrimental disease. During this research a first time investigation was performed on the proteome of E. amylovora, grown inside a susceptible host plant. This bacterium is the causal agent of fire blight, which can affect most members of the Rosaceae family including apple and pear. To do so, an artificial infection model on shoots of apple rootstocks was optimized and employed. When infection was systemic, bacterial cells were extracted from the plant tissue followed by extraction of the proteins from the bacteria. Further processing of the proteins was done by using a 2-D fluorescence difference gel electrophoresis analysis followed by mass spectrometry. By the use of two strains differing in their virulent ability, we were able to draw conclusions concerning virulence and behavior of different strains inside the host. This research provides a model to investigate plant-pathogen interactions and more importantly, we identified possible new targets for the development of novel control methods against this devastating disease. Copyright © 2016 Elsevier B.V. All rights reserved.

Induction of Xa10-like Genes in Rice Cultivar Nipponbare Confers Disease Resistance to Rice Bacterial Blight.

PubMed

Wang, Jun; Tian, Dongsheng; Gu, Keyu; Yang, Xiaobei; Wang, Lanlan; Zeng, Xuan; Yin, Zhongchao

2017-06-01

Bacterial blight of rice, caused by Xanthomonas oryzae pv. oryzae, is one of the most destructive bacterial diseases throughout the major rice-growing regions in the world. The rice disease resistance (R) gene Xa10 confers race-specific disease resistance to X. oryzae pv. oryzae strains that deliver the corresponding transcription activator-like (TAL) effector AvrXa10. Upon bacterial infection, AvrXa10 binds specifically to the effector binding element in the promoter of the R gene and activates its expression. Xa10 encodes an executor R protein that triggers hypersensitive response and activates disease resistance. 'Nipponbare' rice carries two Xa10-like genes in its genome, of which one is the susceptible allele of the Xa23 gene, a Xa10-like TAL effector-dependent executor R gene isolated recently from 'CBB23' rice. However, the function of the two Xa10-like genes in disease resistance to X. oryzae pv. oryzae strains has not been investigated. Here, we designated the two Xa10-like genes as Xa10-Ni and Xa23-Ni and characterized their function for disease resistance to rice bacterial blight. Both Xa10-Ni and Xa23-Ni provided disease resistance to X. oryzae pv. oryzae strains that deliver the matching artificially designed TAL effectors (dTALE). Transgenic rice plants containing Xa10-Ni and Xa23-Ni under the Xa10 promoter provided specific disease resistance to X. oryzae pv. oryzae strains that deliver AvrXa10. Xa10-Ni and Xa23-Ni knock-out mutants abolished dTALE-dependent disease resistance to X. oryzae pv. oryzae. Heterologous expression of Xa10-Ni and Xa23-Ni in Nicotiana benthamiana triggered cell death. The 19-amino-acid residues at the N-terminal regions of XA10 or XA10-Ni are dispensable for their function in inducing cell death in N. benthamiana and the C-terminal regions of XA10, XA10-Ni, and XA23-Ni are interchangeable among each other without affecting their function. Like XA10, both XA10-Ni and XA23-Ni locate to the endoplasmic reticulum (ER) membrane, show self-interaction, and induce ER Ca 2+ depletion in leaf cells of N. benthamiana. The results indicate that Xa10-Ni and Xa23-Ni in Nipponbare encode functional executor R proteins, which induce cell death in both monocotyledonous and dicotyledonous plants and have the potential of being engineered to provide broad-spectrum disease resistance to plant-pathogenic Xanthomonas spp.

Ozone injury and infection of potato leaves by Botrytis cinerea

DOE Office of Scientific and Technical Information (OSTI.GOV)

Manning, W.J.; Feder, W.A.; Perkins, I.

1969-09-01

Symptoms of ozone injury were observed on older leaves of potato cultivars Norland and Katahdin under experimental conditions. This symptom expression closely resembled flecks observed on potato leaves also blighted by Botrytis cinerea in the field. Inoculation of ozone-injured and noninjured potato leaves with B. cinerea showed that infection was more rapid and disease development more severe on ozone-injured leaves. Infection was frequently observed to originate in ozone-injured leaf areas. Ozone injury, under experimental conditions, appeared to increase the susceptibility of potato leaves to infection by B. cinerea. 6 references.

Mapping of SnTox3-Snn3 as a major determinant of field susceptibility to Septoria nodorum leaf blotch in the SHA3/CBRD x Naxos population

USDA-ARS?s Scientific Manuscript database

Parastagonospora nodorum is a necrotrophic pathogen of wheat, causing Septoria nodorum blotch (SNB) affecting both the leaf and glume. P. nodorum is the major leaf blotch pathogen on spring wheat in Norway. Resistance to the disease is quantitative, but several host-specific interactions between nec...

Genome analysis of the ubiquitous boxwood pathogen Pseudonectria foliicola: A small fungal genome with an increased cohort of genes associated with loss of virulence

USDA-ARS?s Scientific Manuscript database

Boxwood plants are affected by many different diseases caused by fungi. Some boxwood diseases are deadly and quickly kill the infected plants, but with others, the plant can survive and even thrive when infected. The fungus that causes volutella blight is the most common of these weak boxwood pathog...

Development of a PCR-RFLP method based on the transcription elongation factor 1-a gene to differentiate Fusarium graminearum from other species within the Fusarium graminearum species complex

USDA-ARS?s Scientific Manuscript database

Fusarium head blight (FHB) is a destructive disease of cereals crops worldwide and a major food safety concern due to grain contamination with trichothecenes and other mycotoxins. Fusarium graminearum, a member of the Fusarium graminearum species complex (FGSC) is the dominant FHB pathogen in many p...

Standardizing the nomenclature for clonal lineages of the sudden oak death pathogen, Phytophthora ramorum

Treesearch

N.J. Grünwald; E.M. Goss; K. Ivors; M. Garbelotto; F.N. Martin; S. Prospero; E. Hansen; P.J.M. Bonants; R.C. Hamelin; G. Chastagner; S. Werres; D.M. Rizzo; G. Abad; P. Beales; G.J. Bilodeau; C.L. Blomquist; C. Brasier; S.C. Brière; A. Chandelier; J.M. Davidson; S. Denman; M. Elliott; S.J. Frankel; E.M. Goheen; H. de Gruyter; K. Heungens; D. James; A. Kanaskie; M.G. McWilliams; W. Man in ' t Veld; E. Moralejo; N.K. Osterbauer; M.E. Palm; J.L. Parke; A.M. Perez Sierra; S.F. Shamoun; N. Shishkoff; P.W. Tooley; A.M. Vettraino; J. Webber; T.L. Widmer

2009-01-01

Phytophthora ramorum, the causal agent of sudden oak death and ramorum blight, is known to exist as three distinct clonal lineages which can only be distinguished by performing molecular marker-based analyses. However, in the recent literature there exists no consensus on naming of these lineages. Here we propose a system for naming clonal lineages of P. ramorum based...

Identification of the infection route of a Fusarium seed pathogen into nondormant Bromus tectorum seeds

Treesearch

JanaLynn Franke; Brad Geary; Susan E. Meyer

2014-01-01

The genus Fusarium has a wide host range and causes many different forms of plant disease. These include seed rot and seedling blight diseases of cultivated plants. The diseases caused by Fusarium on wild plants are less well-known. In this study, we examined disease development caused by Fusarium sp. n on nondormant seeds of the important rangeland weed Bromus...

The outer membrane protein TolC is required for phytoalexin resistance and virulence of the fire blight pathogen Erwinia amylovora.

PubMed

Al-Karablieh, Nehaya; Weingart, Helge; Ullrich, Matthias S

2009-07-01

Erwinia amylovora causes fire blight on several plant species such as apple and pear, which produce diverse phytoalexins as defence mechanisms. An evolutionary successful pathogen thus must develop resistance mechanisms towards these toxic compounds. The E. amylovora outer membrane protein, TolC, might mediate phytoalexin resistance through its interaction with the multidrug efflux pump, AcrAB. To prove this, a tolC mutant and an acrB/tolC double mutant were constructed. The minimal inhibitory concentrations of diverse antimicrobials and phytoalexins were determined for these mutants and compared with that of a previously generated acrB mutant. The tolC and arcB/tolC mutants were considerably more susceptible than the wild type but showed similar levels as the acrB mutant. The results clearly indicated that neither TolC nor AcrAB significantly interacted with other transport systems during the efflux of the tested toxic compounds. Survival and virulence assays on inoculated apple plants showed that pathogenicity and the ability of E. amylovora to colonize plant tissue were equally impaired by mutations of tolC and acrB/tolC. Our results allowed the conclusion that TolC plays an important role as a virulence and fitness factor of E. amylovora by mediating resistance towards phytoalexins through its exclusive interaction with AcrAB. © 2009 The Authors. Journal compilation © 2009 Society for Applied Microbiology and Blackwell Publishing Ltd.

Integrating marker-assisted background analysis with foreground selection for pyramiding bacterial blight resistance genes into Basmati rice.

PubMed

Baliyan, Nikita; Malik, Rekha; Rani, Reema; Mehta, Kirti; Vashisth, Urvashi; Dhillon, Santosh; Boora, Khazan Singh

2018-01-01

Bacterial leaf blight (BB), caused by the bacterium Xanthomonas oryzae pv. Oryzae (Xoo), is the major constraint amongst rice diseases in India. CSR-30 is a very popular high-yielding, salt-tolerant Basmati variety widely grown in Haryana, India, but highly susceptible to BB. In the present study, we have successfully introgressed three BB resistance genes (Xa21, xa13 and xa5) from BB-resistant donor variety IRBB-60 into the BB-susceptible Basmati variety CSR-30 through marker-assisted selection (MAS) exercised with stringent phenotypic selection without compromising the Basmati traits. Background analysis using 131 polymorphic SSR markers revealed that recurrent parent genome (RPG) recovery ranged up to 97.1% among 15 BC 3 F 1 three-gene-pyramided genotypes. Based on agronomic evaluation, BB reaction, aroma, percentage recovery of RPG, and grain quality evaluation, four genotypes, viz., IC-R28, IC-R68, IC-R32, and IC-R42, were found promising and advanced to BC 3 F 2 generation. Copyright © 2017 Académie des sciences. Published by Elsevier Masson SAS. All rights reserved.

Mechanisms of induced susceptibility to Diplodia tip blight in drought-stressed Austrian pine.

PubMed

Sherwood, Patrick; Villari, Caterina; Capretti, Paolo; Bonello, Pierluigi

2015-05-01

Plants experiencing drought stress are frequently more susceptible to pathogens, likely via alterations in physiology that create favorable conditions for pathogens. Common plant responses to drought include the production of reactive oxygen species (ROS) and the accumulation of free amino acids (AAs), particularly proline. These same phenomena also frequently occur during pathogenic attack. Therefore, drought-induced perturbations in AA and ROS metabolism could potentially contribute to the observed enhanced susceptibility. Furthermore, nitrogen (N) availability can influence AA accumulation and affect plant resistance, but its contributions to drought-induced susceptibility are largely unexplored. Here we show that drought induces accumulation of hydrogen peroxide (H2O2) in Austrian pine (Pinus nigra Arnold) shoots, but that shoot infection by the blight and canker pathogen Diplodia sapinea (Fr.) Fuckel leads to large reductions in H2O2 levels in droughted plants. In in vitro assays, H2O2 was toxic to D. sapinea, and the fungus responded to this oxidative stress by increasing catalase and peroxidase activities, resulting in substantial H2O2 degradation. Proline increased in response to drought and infection when examined independently, but unlike all other AAs, proline further increased in infected shoots of droughted trees. In the same tissues, the proline precursor, glutamate, decreased significantly. Proline was found to protect D. sapinea from H2O2 damage, while also serving as a preferred N source in vitro. Fertilization increased constitutive and drought-induced levels of some AAs, but did not affect plant resistance. A new model integrating interactions of proline and H2O2 metabolism with drought and fungal infection of plants is proposed. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

A generic model to simulate air-borne diseases as a function of crop architecture.

PubMed

Casadebaig, Pierre; Quesnel, Gauthier; Langlais, Michel; Faivre, Robert

2012-01-01

In a context of pesticide use reduction, alternatives to chemical-based crop protection strategies are needed to control diseases. Crop and plant architectures can be viewed as levers to control disease outbreaks by affecting microclimate within the canopy or pathogen transmission between plants. Modeling and simulation is a key approach to help analyze the behaviour of such systems where direct observations are difficult and tedious. Modeling permits the joining of concepts from ecophysiology and epidemiology to define structures and functions generic enough to describe a wide range of epidemiological dynamics. Additionally, this conception should minimize computing time by both limiting the complexity and setting an efficient software implementation. In this paper, our aim was to present a model that suited these constraints so it could first be used as a research and teaching tool to promote discussions about epidemic management in cropping systems. The system was modelled as a combination of individual hosts (population of plants or organs) and infectious agents (pathogens) whose contacts are restricted through a network of connections. The system dynamics were described at an individual scale. Additional attention was given to the identification of generic properties of host-pathogen systems to widen the model's applicability domain. Two specific pathosystems with contrasted crop architectures were considered: ascochyta blight on pea (homogeneously layered canopy) and potato late blight (lattice of individualized plants). The model behavior was assessed by simulation and sensitivity analysis and these results were discussed against the model ability to discriminate between the defined types of epidemics. Crop traits related to disease avoidance resulting in a low exposure, a slow dispersal or a de-synchronization of plant and pathogen cycles were shown to strongly impact the disease severity at the crop scale.

Clues to an evolutionary mystery: the genes for T-toxin, enabler of the devastating 1970 Southern Corn Leaf Blight epidemic, are present in ancestral species, suggesting an ancient origin.

PubMed

Condon, Bradford J; Elliott, Candace E; Gonzalez, Jonathan; Yun, Sung-Hwan; Akagi, Yasunori; Wiesner-Hanks, Tyr; Kodama, Motoichiro; Turgeon, Gillian

2018-05-24

The Southern Corn Leaf Blight epidemic of 1970 devastated fields of T-cytoplasm corn planted in monoculture throughout the eastern US. The epidemic was driven by race T, a previously unseen race of Cochliobolus heterostrophus. A second fungus, Phyllosticta zeae-maydis, with the same biological specificity, appeared coincidentally. Race T produces T-toxin, while P. zeae-maydis produces PM-toxin, both host selective polyketide toxins necessary for supervirulence. Present abundance of genome sequences offers an opportunity to tackle the evolutionary origins of T- and PM- toxin biosynthetic genes, previously thought unique to these species. Using the C. heterostrophus genes as probes, we identified orthologs in six additional Dothideomycete and three Eurotiomycete species. In stark contrast to the genetically fragmented race T Tox1 locus which encodes these genes, all newly found Tox1-like genes in other species reside at a single collinear locus. This compact arrangement, phylogenetic analyses, comparisons of Tox1 protein tree topology to a species tree, and Tox1 gene characteristics suggest that the locus is ancient and that some species, including C. heterostrophus, gained Tox1 by horizontal gene transfer. C. heterostrophus and P. zeae-maydis did not exchange Tox1 DNA at the time of the SCLB epidemic, but how they acquired Tox1 remains uncertain. The presence of additional genes in Tox1-like clusters of other species, but not in C. heterostrophus and P. zeae-maydis, suggests that the metabolites produced differ from T- and PM-toxin.

Organization and evolution of mating-type genes in three Stagonosporopsis species causing gummy stem blight of cucurbits and leaf spot and dry rot of papaya.

PubMed

Li, Hao-Xi; Gottilla, Thomas M; Brewer, Marin Talbot

2017-10-01

Population divergence and speciation of closely related lineages can result from reproductive differences leading to genetic isolation. An increasing number of fungal diseases of plants and animals have been determined to be caused by morphologically indistinguishable species that are genetically distinct, thereby representing cryptic species. We were interested in identifying if mating systems among three Stagonosporopsis species (S. citrulli, S. cucurbitacearum, and S. caricae) causing gummy stem blight (GSB) of cucurbits or leaf spot and dry rot of papaya differed, possibly underlying species divergence. Additionally, we were interested in identifying evolutionary pressures acting on the genes controlling mating in these fungi. The mating-type loci (MAT1) of three isolates from each of the three species were identified in draft genome sequences. For the three species, MAT1 was structurally identical and contained both mating-type genes necessary for sexual reproduction, which suggests that all three species are homothallic. However, both MAT1-1-1 and MAT1-2-1 were divergent among species showing rapid evolution with a much greater number of amino acid-changing substitutions detected for the reproductive genes compared with genes flanking MAT1. Positive selection was detected in MAT1-2-1, especially in the highly conserved high mobility group (MATA_HMG-box) domain. Thus, the mating-type genes are rapidly evolving in GSB fungi, but a difference in mating systems among the three species does not underlie their divergence. Copyright © 2017 British Mycological Society. Published by Elsevier Ltd. All rights reserved.

Transcriptome and proteome analysis of Eucalyptus infected with Calonectria pseudoreteaudii.

PubMed

Chen, Quanzhu; Guo, Wenshuo; Feng, Lizhen; Ye, Xiaozhen; Xie, Wanfeng; Huang, Xiuping; Liu, Jinyan

2015-02-06

Cylindrocladium leaf blight is one of the most severe diseases in Eucalyptus plantations and nurseries. There are Eucalyptus cultivars with resistance to the disease. However, little is known about the defense mechanism of resistant cultivars. Here, we investigated the transcriptome and proteome of Eucalyptus leaves (E. urophylla×E. tereticornis M1), infected or not with Calonectria pseudoreteaudii. A total of 8585 differentially expressed genes (|log2 ratio| ≥1, FDR ≤0.001) at 12 and 24hours post-inoculation were detected using RNA-seq. Transcriptional changes for five genes were further confirmed by qRT-PCR. A total of 3680 proteins at the two time points were identified using iTRAQ technique.The combined transcriptome and proteome analysis revealed that the shikimate/phenylpropanoid pathway, terpenoid biosynthesis, signalling pathway (jasmonic acid and sugar) were activated. The data also showed that some proteins (WRKY33 and PR proteins) which have been reported to involve in plant defense response were up-regulated. However, photosynthesis, nucleic acid metabolism and protein metabolism were impaired by the infection of C. pseudoreteaudii. This work will facilitate the identification of defense related genes and provide insights into Eucalyptus defense responses to Cylindrocladium leaf blight. In this study, a total of 130 proteins and genes involved in the shikimate/phenylpropanoid pathway, terpenoid biosynthesis, signalling pathway, cell transport, carbohydrate and energy metabolism, nucleic acid metabolism and protein metabolism in Eucalyptus leaves after infected with C. pseudoreteaudii were identified. This is the first report of a comprehensive transcriptomic and proteomic analysis of Eucalyptus in response to Calonectria sp. Copyright © 2014 Elsevier B.V. All rights reserved.

XopN-T3SS effector of Xanthomonas axonopodis pv. punicae localizes to the plasma membrane and modulates ROS accumulation events during blight pathogenesis in pomegranate.

PubMed

Kumar, Rishikesh; Soni, Madhvi; Mondal, Kalyan K

2016-12-01

Bacterial blight caused by Xanthomonas axonopodis pv. punicae (Xap) is a major disease of pomegranate. Xap secretes effector proteins via type III secretion system (T3SS) to suppress pathogen-associated molecular pattern (PAMP)-triggered plant immunity (PTI). Previously we reported that XopN, a conserved effector of Xap, modulate in planta bacterial growth, and blight disease. In continuation to that here we report the deletion of XopN from Xap caused higher accumulation of reactive oxygen species (ROS) including H 2 O 2 and O 2 - . We quantitatively assessed the higher accumulation of H 2 O 2 in pomegranate leaves infiltrated with Xap ΔxopN compared to Xap wild-type. We analysed that 1.5 to 3.3 fold increase in transcript expression of ROS and flg22-inducible genes, namely FRK1, GST1, WRKY29, PR1, PR2 and PR5 in Arabidopsis when challenged with Xap ΔxopN; contrary, the up-regulation of all the genes were compromised when challenged with either Xap wild-type or Xap ΔxopN+xopN. Further, we demonstrated the plasma-membrane based localization of XopN protein both in its natural and experimental hosts. All together, the present study suggested that XopN-T3SS effector of Xap gets localized in the plasma membrane and suppresses ROS-mediated early defense responses during blight pathogenesis in pomegranate. Copyright © 2016 Elsevier GmbH. All rights reserved.

Generation of advanced fire blight-resistant apple (Malus × domestica) selections of the fifth generation within 7 years of applying the early flowering approach.

PubMed

Schlathölter, Ina; Jänsch, Melanie; Flachowsky, Henryk; Broggini, Giovanni Antonio Lodovico; Hanke, Magda-Viola; Patocchi, Andrea

2018-06-01

The approach presented here can be applied to reduce the time needed to introduce traits from wild apples into null segregant advanced selections by one-fourth. Interesting traits like resistances to pathogens are often found within the wild apple gene pool. However, the long juvenile phase of apple seedlings hampers the rapid introduction of these traits into new cultivars. The rapid crop cycle breeding approach used in this paper is based on the overexpression of the birch (Betula pendula) MADS4 transcription factor in apple. Using the early flowering line T1190 and 'Evereste' as source of the fire blight resistance (Fb_E locus), we successfully established 18 advanced selections of the fifth generation in the greenhouse within 7 years. Fifteen individuals showed the habitus expected of a regular apple seedling, while three showed very short internodes. The null segregants possessing a regular habitus maintained the high level of fire blight resistance typical for 'Evereste'. Using SSR markers, we estimated the percentage of genetic drag from 'Evereste' still associated with Fb_E on linkage group 12 (LG12). Eight out of the 18 selections had only 4% of 'Evereste' genome left. Since genotypes carrying the apple scab resistance gene Rvi6 and the fire blight resistance QTL Fb_F7 were used as parents in the course of the experiments, these resistances were also identified in some of the null segregants. One seedling is particularly interesting as, beside Fb_E, it also carries Fb_F7 heterozygously and Rvi6 homozygously. If null segregants obtained using this method will be considered as not genetically modified in Europe, as is already the case in the USA, this genotype could be a very promising parent for breeding new fire blight and scab-resistant apple cultivars in European apple breeding programs.

Transcriptome analysis of WRKY gene family in Oryza officinalis Wall ex Watt and WRKY genes involved in responses to Xanthomonas oryzae pv. oryzae stress

PubMed Central

Jiang, Chunmiao; Shen, Qingxi J.; Wang, Bo; He, Bin; Xiao, Suqin; Chen, Ling; Yu, Tengqiong; Ke, Xue; Zhong, Qiaofang; Fu, Jian; Chen, Yue; Wang, Lingxian; Yin, Fuyou; Zhang, Dunyu; Ghidan, Walid; Huang, Xingqi; Cheng, Zaiquan

2017-01-01

Oryza officinalis Wall ex Watt, a very important and special wild rice species, shows abundant genetic diversity and disease resistance features, especially high resistance to bacterial blight. The molecular mechanisms of bacterial blight resistance in O. officinalis have not yet been elucidated. The WRKY transcription factor family is one of the largest gene families involved in plant growth, development and stress response. However, little is known about the numbers, structure, molecular phylogenetics, and expression of the WRKY genes under Xanthomonas oryzae pv. oryzae (Xoo) stress in O. officinalis due to lacking of O. officinalis genome. Therefore, based on the RNA-sequencing data of O. officinalis, we performed a comprehensive study of WRKY genes in O. officinalis and identified 89 OoWRKY genes. Then 89 OoWRKY genes were classified into three groups based on the WRKY domains and zinc finger motifs. Phylogenetic analysis strongly supported that the evolution of OoWRKY genes were consistent with previous studies of WRKYs, and subgroup IIc OoWRKY genes were the original ancestors of some group II and group III OoWRKYs. Among the 89 OoWRKY genes, eight OoWRKYs displayed significantly different expression (>2-fold, p<0.01) in the O. officinalis transcriptome under Xoo strains PXO99 and C5 stress 48 h, suggesting these genes might play important role in PXO99 and C5 stress responses in O. officinalis. QRT-PCR analysis and confirmation of eight OoWRKYs expression patterns revealed that they responded strongly to PXO99 and C5 stress 24 h, 48 h, and 72 h, and the trends of these genes displaying marked changes were consistent with the 48 h RNA-sequencing data, demonstrated these genes played important roles in response to biotic stress and might even involved in the bacterial blight resistance. Tissue expression profiles of eight OoWRKY genes revealed that they were highly expressed in root, stem, leaf, and flower, especially in leaf (except OoWRKY71), suggesting these genes might be also important for plant growth and organ development. In this study, we analyzed the WRKY family of transcription factors in O.officinalis. Insight was gained into the classification, evolution, and function of the OoWRKY genes, revealing the putative roles of eight significantly different expression OoWRKYs in Xoo strains PXO99 and C5 stress responses in O.officinalis. This study provided a better understanding of the evolution and functions of O. officinalis WRKY genes, and suggested that manipulating eight significantly different expression OoWRKYs would enhance resistance to bacterial blight. PMID:29190793

Transcriptome analysis of WRKY gene family in Oryza officinalis Wall ex Watt and WRKY genes involved in responses to Xanthomonas oryzae pv. oryzae stress.

PubMed

Jiang, Chunmiao; Shen, Qingxi J; Wang, Bo; He, Bin; Xiao, Suqin; Chen, Ling; Yu, Tengqiong; Ke, Xue; Zhong, Qiaofang; Fu, Jian; Chen, Yue; Wang, Lingxian; Yin, Fuyou; Zhang, Dunyu; Ghidan, Walid; Huang, Xingqi; Cheng, Zaiquan

2017-01-01

Oryza officinalis Wall ex Watt, a very important and special wild rice species, shows abundant genetic diversity and disease resistance features, especially high resistance to bacterial blight. The molecular mechanisms of bacterial blight resistance in O. officinalis have not yet been elucidated. The WRKY transcription factor family is one of the largest gene families involved in plant growth, development and stress response. However, little is known about the numbers, structure, molecular phylogenetics, and expression of the WRKY genes under Xanthomonas oryzae pv. oryzae (Xoo) stress in O. officinalis due to lacking of O. officinalis genome. Therefore, based on the RNA-sequencing data of O. officinalis, we performed a comprehensive study of WRKY genes in O. officinalis and identified 89 OoWRKY genes. Then 89 OoWRKY genes were classified into three groups based on the WRKY domains and zinc finger motifs. Phylogenetic analysis strongly supported that the evolution of OoWRKY genes were consistent with previous studies of WRKYs, and subgroup IIc OoWRKY genes were the original ancestors of some group II and group III OoWRKYs. Among the 89 OoWRKY genes, eight OoWRKYs displayed significantly different expression (>2-fold, p<0.01) in the O. officinalis transcriptome under Xoo strains PXO99 and C5 stress 48 h, suggesting these genes might play important role in PXO99 and C5 stress responses in O. officinalis. QRT-PCR analysis and confirmation of eight OoWRKYs expression patterns revealed that they responded strongly to PXO99 and C5 stress 24 h, 48 h, and 72 h, and the trends of these genes displaying marked changes were consistent with the 48 h RNA-sequencing data, demonstrated these genes played important roles in response to biotic stress and might even involved in the bacterial blight resistance. Tissue expression profiles of eight OoWRKY genes revealed that they were highly expressed in root, stem, leaf, and flower, especially in leaf (except OoWRKY71), suggesting these genes might be also important for plant growth and organ development. In this study, we analyzed the WRKY family of transcription factors in O.officinalis. Insight was gained into the classification, evolution, and function of the OoWRKY genes, revealing the putative roles of eight significantly different expression OoWRKYs in Xoo strains PXO99 and C5 stress responses in O.officinalis. This study provided a better understanding of the evolution and functions of O. officinalis WRKY genes, and suggested that manipulating eight significantly different expression OoWRKYs would enhance resistance to bacterial blight.

Translations on USSR Science and Technology, Biomedical and Behavioral Sciences, Number 43

DTIC Science & Technology

1978-08-15

resistance to the pathogen of bacterial angular blight is related to their resistance to powdery mildew (A. P. Khar’kova, N. M. Rudenko), powdery ...waste ■ Raw material for hvdrolvsates . Hydrolysate components, % flax & hemp fiber rice straw sun- flower stalks grape vines wheat straw...hydrolysates of rice and wheat straw, sunflower, stalks, grapevine cuttings, spent tanbark, flax and hemp fiber. Chromatographie analysis defined the

Overexpression of wheat lipid transfer protein gene TaLTP5 increases resistances to Cochliobolus sativus and Fusarium graminearum in transgenic wheat.

PubMed

Zhu, Xiuliang; Li, Zhao; Xu, Huijun; Zhou, Miaoping; Du, Lipu; Zhang, Zengyan

2012-08-01

The fungus Cochliobolus sativus is the main pathogen of common root rot, a serious soil-borne disease of wheat (Triticum aestivum L.). The fungus Fusarium graminearum is the primary pathogen of Fusarium head blight, a devastating disease of wheat worldwide. In this study, the wheat lipid transfer protein gene, TaLTP5, was cloned and evaluated for its ability to suppress disease development in transgenic wheat. TaLTP5 expression was induced after C. sativus infection. The TaLTP5 expression vector, pA25-TaLTP5, was constructed and bombarded into Chinese wheat variety Yangmai 18. Six TaLTP5 transgenic wheat lines were established and characterized. PCR and Southern blot analyses indicated that the introduced TaLTP5 gene was integrated into the genomes of six transgenic wheat lines by distinct patterns, and heritable. RT-PCR and real-time quantitative RT-PCR revealed that the TaLTP5 gene was over-expressed in the transgenic wheat lines compared to segregants lacking the transgene and wild-type wheat plants. Following challenge with C. sativus or F. graminearum, all six transgenic lines overexpressing TaLTP5 exhibited significantly enhanced resistance to both common root rot and Fusarium head blight compared to the untransformed wheat Yangmai 18.

Direct suppression of a rice bacterial blight (Xanthomonas oryzae pv. oryzae) by monoterpene (S)-limonene.

PubMed

Lee, Gun Woong; Chung, Moon-Soo; Kang, Mihyung; Chung, Byung Yeoup; Lee, Sungbeom

2016-05-01

Rice bacterial blight, caused by Xanthomonas oryzae pv. oryzae (Xoo), is a severe disease of rice plants. Upon pathogen infection, rice biosynthesizes phytoalexins, including diterpenoids such as momilactones, phytocassanes, and oryzalexins. However, information on headspace volatiles in response to Xoo infection is limited. We have examined headspace volatile terpenes, induced by the infection of Xoo, and investigated their biological roles in the rice plant. Monoterpenes α-thujene, α-pinene, sabinene, myrcene, α-terpene, and (S)-limonene and sesquiterpenes cyclosativene, α-copaene, and β-elemene were detected from 1-week-old Xoo-infected rice seedlings, by solid-phase microextraction-gas chromatography-mass spectrometry. All monoterpenes were constitutively released from rice seedlings before Xoo infection. However, (S)-limonene emission was further elicited after exposure of the seedlings to Xoo in coincidence with upregulation of limonene synthase gene (OsTPS20) transcripts. Only the stereospecific (S)-limonene [and not (R)-limonene or other monoterpenes] severely inhibited Xoo growth, as confirmed by disc diffusion and liquid culture assays. Rice seedlings showed suppressed pathogenic symptoms suggestive of resistance to Xoo infection after foliar treatment with (S)-limonene. Collectively, our findings suggest that (S)-limonene is a volatile phytoanticipin, which plays a significant role in suppressing Xoo growth in rice seedlings.

Investigating alternative strategies for managing bacterial angular leaf spot in strawberry nursery production

USDA-ARS?s Scientific Manuscript database

The focus of this article is to discuss some of the approaches we have tested for managing the bacterial pathogen Xanthomonas fragariae in infected strawberry nursery stock. X. fragariae causes angular leaf spot (ALS) in strawberry. The pathogen is transmitted to production fields almost exclusively...

RAV transcription factors are essential for disease resistance against cassava bacterial blight via activation of melatonin biosynthesis genes.

PubMed

Wei, Yunxie; Chang, Yanli; Zeng, Hongqiu; Liu, Guoyin; He, Chaozu; Shi, Haitao

2018-01-01

With 1 AP2 domain and 1 B3 domain, 7 MeRAVs in apetala2/ethylene response factor (AP2/ERF) gene family have been identified in cassava. However, the in vivo roles of these remain unknown. Gene expression assays showed that the transcripts of MeRAVs were commonly regulated after Xanthomonas axonopodis pv manihotis (Xam) and MeRAVs were specifically located in plant cell nuclei. Through virus-induced gene silencing (VIGS) in cassava, we found that MeRAV1 and MeRAV2 are essential for plant disease resistance against cassava bacterial blight, as shown by the bacterial propagation of Xam in plant leaves. Through VIGS in cassava leaves and overexpression in cassava leave protoplasts, we found that MeRAV1 and MeRAV2 positively regulated melatonin biosynthesis genes and the endogenous melatonin level. Further investigation showed that MeRAV1 and MeRAV2 are direct transcriptional activators of 3 melatonin biosynthesis genes in cassava, as evidenced by chromatin immunoprecipitation-PCR in cassava leaf protoplasts and electrophoretic mobility shift assay. Moreover, cassava melatonin biosynthesis genes also positively regulated plant disease resistance. Taken together, this study identified MeRAV1 and MeRAV2 as common and upstream transcription factors of melatonin synthesis genes in cassava and revealed a model of MeRAV1 and MeRAV2-melatonin biosynthesis genes-melatonin level in plant disease resistance against cassava bacterial blight. © 2017 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Transcriptome dynamics of a susceptible wheat upon Fusarium head blight reveals that molecular responses to Fusarium graminearum infection fit over the grain development processes.

PubMed

Chetouhi, Cherif; Bonhomme, Ludovic; Lasserre-Zuber, Pauline; Cambon, Florence; Pelletier, Sandra; Renou, Jean-Pierre; Langin, Thierry

2016-03-01

In many plant/pathogen interactions, host susceptibility factors are key determinants of disease development promoting pathogen growth and spreading in plant tissues. In the Fusarium head blight (FHB) disease, the molecular basis of wheat susceptibility is still poorly understood while it could provide new insights into the understanding of the wheat/Fusarium graminearum (Fg) interaction and guide future breeding programs to produce cultivars with sustainable resistance. To identify the wheat grain candidate genes, a genome-wide gene expression profiling was performed in the French susceptible wheat cultivar, Recital. Gene-specific two-way ANOVA of about 40 K transcripts at five grain developmental stages identified 1309 differentially expressed genes. Out of these, 536 were impacted by the Fg effect alone. Most of these Fg-responsive genes belonged to biological and molecular functions related to biotic and abiotic stresses indicating the activation of common stress pathways during susceptibility response of wheat grain to FHB. This analysis revealed also 773 other genes displaying either specific Fg-responsive profiles along with grain development stages or synergistic adjustments with the grain development effect. These genes were involved in various molecular pathways including primary metabolism, cell death, and gene expression reprogramming. An increasingly complex host response was revealed, as was the impact of both Fg infection and grain ontogeny on the transcription of wheat genes. This analysis provides a wealth of candidate genes and pathways involved in susceptibility responses to FHB and depicts new clues to the understanding of the susceptibility determinism in plant/pathogen interactions.

Development of breeding lines with three pyramided resistance genes that confer broad-spectrum bacterial blight resistance and their molecular analysis in rice.

PubMed

Suh, Jung-Pil; Jeung, Ji-Ung; Noh, Tae-Hwan; Cho, Young-Chan; Park, So-Hyun; Park, Hyun-Su; Shin, Mun-Sik; Kim, Chung-Kon; Jena, Kshirod K

2013-02-08

The development of resistant cultivars has been the most effective and economical strategy to control bacterial leaf blight (BB) disease of rice caused by Xanthomonas oryzae pv. oryzae (Xoo). Molecular markers have made it possible to identify and pyramid valuable genes of agronomic importance in resistance rice breeding. In this study, three resistance genes (Xa4 + xa5 + Xa21) were transferred from an indica donor (IRBB57), using a marker-assisted backcrossing (MAB) breeding strategy, into a BB-susceptible elite japonica rice cultivar, Mangeumbyeo, which is high yielding with good grain quality. Our analysis led to the development of three elite advanced backcross breeding lines (ABL) with three resistance genes by foreground and phenotypic selection in a japonica genetic background without linkage drag. The background genome recovery of the ABL expressed more than 92.1% using genome-wide SSR marker analysis. The pathogenicity assays of three resistance-gene-derived ABL were conducted under glasshouse conditions with the 18 isolates of Xoo prevalent in Korea. The ABL exhibited very small lesion lengths, indicating a hypersensitive reaction to all 18 isolates of Xoo, with agronomic and grain quality traits similar to those of the recurrent parent. Pyramiding the resistance genes Xa4, xa5 and Xa21 provided a higher resistance to Xoo than the introduction of the individual resistance genes. Additionally, the combination of two dominant and one recessive BB resistance gene did not express any negative effect on agronomic traits in the ABL. The strategy of simultaneous foreground and phenotypic selection to introduce multiple R genes is very useful to reduce the cost and the time required for the isolation of desirable recombinants with target resistance genes in rice. The resistance-gene-derived ABL have practical breeding value without a yield penalty by providing broad-spectrum resistance against most of the existing isolates of BB in South Korea and will have a high impact on the yield stability and sustainability of rice productivity.

Silencing of flavanone-3-hydroxylase in apple (Malus × domestica Borkh.) leads to accumulation of flavanones, but not to reduced fire blight susceptibility.

PubMed

Flachowsky, Henryk; Halbwirth, Heidi; Treutter, Dieter; Richter, Klaus; Hanke, Magda-Viola; Szankowski, Iris; Gosch, Christian; Stich, Karl; Fischer, Thilo C

2012-02-01

Transgenic antisense flavanone-3-hydroxylase apple plants were produced to mimic the effect of the agrochemical prohexadione-Ca on apple leaves. This enzyme inhibitor for 2-oxoglutarate dependent dioxygenases is used as a growth retardant and for control of secondary fire blight of leaves. Like using the agent, silencing of flavanone-3-hydroxylase leads to an accumulation of flavanones in leaves, but in contrast not to the formation of 3-deoxyflavonoids. In prohexadione-Ca treated leaves the 3-deoxyflavonoid luteoforol is formed from accumulating flavanones, acting as an antimicrobial compound against the fire blight pathogen Erwinia amylovora. Seemingly, the silencing of just one of the 2-oxoglutarate dependent dioxygenases (in apple also flavonol synthase and anthocyanidin synthase take part downstream in the pathway) does not provide a sufficiently high ratio of flavanones to dihydroflavonols. This seems to be needed to let the dihydroflavonol-4-reductase/flavanone-4-reductase enzyme reduce flavanones to luteoforol, and to let this be reduced by the leucoanthocyanidin-4-reductase/3-deoxyleucoanthocyanidin-4-reductase, each acting with their respective weak secondary activities. Accordingly, also the intended inducible resistance to fire blight by prohexadione-Ca is not observed with the antisense flavanone-3-hydroxylase apple plants. On the other hand, for most transgenic lines with strong flavanone-4-reductase down-regulation, up-regulation of gene expression for the other flavonoid genes was found. This provides further evidence for the feedback regulation of flavonoid gene expression having been previously reported for the prohexadione-Ca inhibited apple plants. Copyright © 2011 Elsevier Masson SAS. All rights reserved.

Development of the First Cisgenic Apple with Increased Resistance to Fire Blight

PubMed Central

Kost, Thomas D.; Gessler, Cesare; Jänsch, Melanie; Flachowsky, Henryk; Patocchi, Andrea; Broggini, Giovanni A. L.

2015-01-01

The generation and selection of novel fire blight resistant apple genotypes would greatly improve the management of this devastating disease, caused by Erwinia amylovora. Such resistant genotypes are currently developed by conventional breeding, but novel breeding technologies including cisgenesis could be an alternative approach. A cisgenic apple line C44.4.146 was regenerated using the cisgene FB_MR5 from wild apple Malus ×robusta 5 (Mr5), and the previously established method involving A. tumefaciens-mediated transformation of the fire blight susceptible cultivar ‘Gala Galaxy’ using the binary vector p9-Dao-FLPi. The line C44.4.146 was shown to carry only the cisgene FB_MR5, controlled by its native regulatory sequences and no transgenes were detected by PCR or Southern blot following heat induced recombinase-mediated elimination of the selectable markers. Although this line contains up to 452 bp of vector sequences, it still matches the original definition of cisgenesis. A single insertion of T-DNA into the genome of 'Gala Galaxy' in chromosome 16 was identified. Transcription of FB_MR5 in line C44.4.146 was similar to the transcription in classically bred descendants of Mr5. Three independent shoot inoculation experiments with a Mr5 avirulent strain of Erwinia amylovora were performed using scissors or syringe. Significantly lower disease symptoms were detected on shoots of the cisgenic line compared to those of untransformed 'Gala Galaxy'. Despite the fact that the pathogen can overcome this resistance by a single nucleotide mutation, this is, to our knowledge, the first prototype of a cisgenic apple with increased resistance to fire blight. PMID:26624292

Recent advances in genes involved in secondary metabolite synthesis, hyphal development, energy metabolism and pathogenicity in Fusarium graminearum (teleomorph Gibberella zeae).

PubMed

Geng, Zongyi; Zhu, Wei; Su, Hao; Zhao, Yong; Zhang, Ke-Qin; Yang, Jinkui

2014-01-01

The ascomycete fungus, Fusarium graminearum (teleomorph Gibberella zeae), is the most common causal agent of Fusarium head blight (FHB), a devastating disease for cereal crops worldwide. F. graminearum produces ascospores (sexual spores) and conidia (asexual spores), which can serve as disease inocula of FHB. Meanwhile, Fusarium-infected grains are often contaminated with mycotoxins such as trichothecenes (TRIs), fumonisins, and zearalenones, among which TRIs are related to the pathogenicity of F. graminearum, and these toxins are hazardous to humans and livestock. In recent years, with the complete genome sequencing of F. graminearum, an increasing number of functional genes involved in the production of secondary metabolites, hyphal differentiation, sexual and asexual reproduction, virulence and pathogenicity have been identified from F. graminearum. In this review, the secondary metabolite synthesis, hyphal development and pathogenicity related genes in F. graminearum were thoroughly summarized, and the genes associated with secondary metabolites, sexual reproduction, energy metabolism, and pathogenicity were highlighted. Copyright © 2013 Elsevier Inc. All rights reserved.

Disaster Relief and Emergency Medical Services (DREAMS): Texas A&M Digital EMS and the Detection and Remediation of Chemical Threat Agents

DTIC Science & Technology

2004-10-01

the bacterial exopolysaccharide has been initiated. The enterobacterium Erwinia amylovora , the fire blight pathogen of rosaceous plants and pome...A&M University Erwinia amylovora bacteriophage ERA 103 plaques surrounded by halos. Task 15: Development of Integrated Microfluidic-based Sensors for...fruit, produces copious amounts of extra cellular polysaccharide (amylovoran), which acts as a host specific toxin during pathogenesis. The E. amylovora

Shoot winter injury and nut cold tolerance: Possible limitations for American chestnut restoration in cold environments? In: Sniezko, Richard A.; Yanchuk, Alvin D.; Kliejunas, John T.; Palmieri, Katharine M.; Alexander, Janice M.; Frankel, Susan J., tech

Treesearch

Thomas M. Saielli; Paul G. Schaberg; Gary J. Hawley; Joshua M. Halman; Kendra M. Gurney

2012-01-01

Approximately 100 years ago, American chestnut (Castanea dentata (Marsh.) Borkh.) was rapidly removed as an overstory tree by the fungal pathogen Cryphonectria parasitica (the causal agent of chestnut blight). Currently, the most effective method of restoration involves the hybridization of American chestnut with the...

A Fungus-Inducible Pepper Carboxylesterase Exhibits Antifungal Activity by Decomposing the Outer Layer of Fungal Cell Walls.

PubMed

Seo, Hyo-Hyoun; Park, Ae Ran; Lee, Hyun-Hwa; Park, Sangkyu; Han, Yun-Jeong; Hoang, Quyen T N; Choi, Gyung Ja; Kim, Jin-Cheol; Kim, Young Soon; Kim, Jeong-Il

2018-05-01

Colletotrichum species are major fungal pathogens that cause devastating anthracnose diseases in many economically important crops. In this study, we observed the hydrolyzing activity of a fungus-inducible pepper carboxylesterase (PepEST) on cell walls of C. gloeosporioides, causing growth retardation of the fungus by blocking appressorium formation. To determine the cellular basis for the growth inhibition, we observed the localization of PepEST on the fungus and found the attachment of the protein on surfaces of conidia and germination tubes. Moreover, we examined the decomposition of cell-wall materials from the fungal surface after reaction with PepEST, which led to the identification of 1,2-dithiane-4,5-diol (DTD) by gas chromatography mass spectrometry analysis. Exogenous DTD treatment did not elicit expression of defense-related genes in the host plant but did trigger the necrosis of C. gloeosporioides. Furthermore, the DTD compound displayed protective effects on pepper fruits and plants against C. gloeosporioides and C. coccodes, respectively. In addition, DTD was also effective in preventing other diseases, such as rice blast, tomato late blight, and wheat leaf rust. Therefore, our results provide evidence that PepEST is involved in hydrolysis of the outmost layer of the fungal cell walls and that DTD has antifungal activity, suggesting an alternative strategy to control agronomically important phytopathogens.

A Circadian Rhythm-Regulated Tomato Gene Is Induced by Arachidonic Acid and Phythophthora infestans Infection1[W

PubMed Central

Weyman, Philip D.; Pan, Zhiqiang; Feng, Qin; Gilchrist, David G.; Bostock, Richard M.

2006-01-01

A cDNA clone of unknown function, DEA1, was isolated from arachidonic acid-treated tomato (Solanum lycopersicum) leaves by differential display PCR. The gene, DEA1, is expressed in response to the programmed cell death-inducing arachidonic acid within 8 h following treatment of a tomato leaflet, 16 h prior to the development of visible cell death. DEA1 transcript levels were also affected by the late blight pathogen, Phytophthora infestans. To gain further insight into the transcriptional regulation of DEA1, the promoter region was cloned by inverse PCR and was found to contain putative stress-, signaling-, and circadian-response elements. DEA1 is highly expressed in roots, stems, and leaves, but not in flowers. Leaf expression of DEA1 is regulated by circadian rhythms during long days with the peak occurring at midday and the low point midway through the dark period. During short days, the rhythm is lost and DEA1 expression becomes constitutive. The predicted DEA1 protein has a conserved domain shared by the eight-cysteine motif superfamily of protease inhibitors, α-amylase inhibitors, seed storage proteins, and lipid transfer proteins. A DEA1-green fluorescent protein fusion protein localized to the plasma membrane in protoplasts and plasmolysis experiments, suggesting that the native protein is associated with the plasmalemma in intact cells. PMID:16361525

Ectopic activation of the rice NLR heteropair RGA4/RGA5 confers resistance to bacterial blight and bacterial leaf streak diseases.

PubMed

Hutin, Mathilde; Césari, Stella; Chalvon, Véronique; Michel, Corinne; Tran, Tuan Tu; Boch, Jens; Koebnik, Ralf; Szurek, Boris; Kroj, Thomas

2016-10-01

Bacterial blight (BB) and bacterial leaf streak (BLS) are important diseases in Oryza sativa caused by Xanthomonas oryzae pv. oryzae (Xoo) and Xanthomonas oryzae pv. oryzicola (Xoc), respectively. In both bacteria, transcription activator-like (TAL) effectors are major virulence determinants that act by transactivating host genes downstream of effector-binding elements (EBEs) bound in a sequence-specific manner. Resistance to Xoo is mostly related to the action of TAL effectors, either by polymorphisms that prevent the induction of susceptibility (S) genes or by executor (R) genes with EBEs embedded in their promoter, and that induce cell death and resistance. For Xoc, no resistance sources are known in rice. Here, we investigated whether the recognition of effectors by nucleotide binding and leucine-rich repeat domain immune receptors (NLRs), the most widespread resistance mechanism in plants, is also able to stop BB and BLS. In one instance, transgenic rice lines harboring the AVR1-CO39 effector gene from the rice blast fungus Magnaporthe oryzae, under the control of an inducible promoter, were challenged with transgenic Xoo and Xoc strains carrying a TAL effector designed to transactivate the inducible promoter. This induced AVR1-CO39 expression and triggered BB and BLS resistance when the corresponding Pi-CO39 resistance locus was present. In a second example, the transactivation of an auto-active NLR by Xoo-delivered designer TAL effectors resulted in BB resistance, demonstrating that NLR-triggered immune responses efficiently control Xoo. This forms the foundation for future BB and BLS disease control strategies, whereupon endogenous TAL effectors will target synthetic promoter regions of Avr or NLR executor genes. © 2016 The Authors The Plant Journal © 2016 John Wiley & Sons Ltd.

Marker-assisted introgression of opaque2 allele for rapid conversion of elite hybrids into quality protein maize.

PubMed

Hossain, Firoz; Muthusamy, Vignesh; Pandey, Neha; Vishwakarma, Ashish K; Baveja, Aanchal; Zunjare, Rajkumar U; Thirunavukkarasu, Nepolean; Saha, Supradip; Manjaiah, Kanchikeri M Manjaiah; Prasanna, Boddupalli M; Gupta, Hari S

2018-03-01

Maize is a valuable source of food and feed worldwide. Maize endosperm protein is, however nutritionally poor due to the reduced levels of two essential amino acids, lysine and tryptophan. In this study, recessive opaque2 (o2) allele that confers enhanced endosperm lysine and tryptophan, was introgressed using marker-assisted backcross breeding into three normal inbred lines (HKI323, HKI1105 and HKI1128). These are the parental lines of three popular medium-maturing single cross hybrids (HM4, HM8 and HM9) in India. Gene-based simple sequence repeat (SSR) markers (umc1066 and phi057) were successfully deployed for introgression of o2 allele. Background selection using genome-based SSRs helped in recovering > 96% of recurrent parent genome. The newly developed quality protein maize (QPM) inbreds showed modified kernels (25-50% opaqueness) coupled with high degree of phenotypic resemblance to the respective recipient lines, including grain yield. In addition, endosperm protein quality showed increased lysine and tryptophan in the inbreds to the range of 52-95% and 47-118%, respectively. The reconstituted QPM hybrids recorded significant enhancement of endosperm lysine (48-74%) and tryptophan (55-100%) in the endosperm. The QPM hybrids exhibited high phenotypic similarity with the original hybrids for morphological and yield contributing traits along with responses to some major diseases like turcicum leaf blight and maydis leaf blight. The grain yield of QPM hybrids was at par with their original versions under multilocation testing. These elite, high-yielding QPM hybrids with improved protein quality have been released and notified for commercial cultivation, and hold significant promise for improving nutritional security.

Fusaric acid is a crucial factor in the disturbance of leaf water imbalance in Fusarium-infected banana plants.

PubMed

Dong, Xian; Ling, Ning; Wang, Min; Shen, Qirong; Guo, Shiwei

2012-11-01

Fusarium wilt of banana is caused by Fusarium oxysporum f. sp. cubense infection. The initial chlorosis symptoms occur progressively from lower to upper leaves, with wilt symptoms subsequently occurring in the whole plant. To determine the effect of the pathogen infection on the gas exchange characteristics and water content in banana leaves, hydroponic experiments with pathogen inoculation were conducted in a greenhouse. Compared with control plants, infected banana seedlings showed a higher leaf temperature as determined by thermal imaging. Reduced stomatal conductance (g(s)) and transpiration rate (E) in infected plants resulted in lower levels of water loss than in control plants. Water potential in heavily diseased plants (II) was significantly reduced and the E/g(s) ratio was higher than in noninfected plants, indicating the occurrence of uncontrolled water loss not regulated by stomata in diseased plants. As no pathogen colonies were detected from the infected plant leaves, the crude toxin was extracted from the pathogen culture and evaluated about the effect on banana plant to further investigate the probable reason of these physiological changes in Fusarium-infected banana leaf. The phytotoxin fusaric acid (FA) was found in the crude toxin, and both crude toxin and pure FA had similar effects as the pathogen infection on the physiological changes in banana leaf. Additionally, FA was present at all positions in diseased plants and its concentration was positively correlated with the incidence of disease symptoms. Taken together, these observations indicated that FA secreted by the pathogen is an important factor involved in the disturbance of leaf temperature, resulting in uncontrolled leaf water loss and electrolyte leakage due to damaging the cell membrane. In conclusion, FA plays a critical role in accelerating the development of Fusarium wilt in banana plants by acting as a phytotoxin. Copyright © 2012 Elsevier Masson SAS. All rights reserved.

Determination and confirmation of nicotinic acid and its analogues and derivates in pear and apple blossoms using high-performance liquid chromatography-diode array-electrospray ionization mass spectrometry.

PubMed

Paternoster, Thomas; Vrhovsek, Urska; Pertot, Ilaria; Duffy, Brion; Gessler, Cesare; Mattivi, Fulvio

2009-11-11

Erwinia amylovora causes fire blight, a serious disease of apple and pear. The bacterial pathogen colonizes the flower stigma and hypanthium, where it multiplies and then invades through natural openings (nectarthodes). E. amylovora requires nicotinic acid as growth factor, and competition for nicotinic acid is being explored as a novel biocontrol strategy. The ability of E. amylovora to substitute nicotinic acid with analogues or derivates as growth factors has not been investigated yet. Furthermore, the presence and/or variable concentration of nicotinic acid and its analogues/derivates in the hypanthium could be associated with the different susceptibilities to fire blight of hosts and nonhosts and with the differential sensitivity to the disease among apple and pear varieties. Currently, no methods to specifically quantify nicotinic acid and nicotinic acid analogues/derivates in the hypanthium of apple and pear blossoms are available. This study demonstrates that E. amylovora can grow using nicotinamide and 6-hydroxynicotinic acid as alternative growth factors to nicotinic acid, but not using 2-hydroxynicotinic acid. A novel HPLC/ES-MS method was developed for the detection and quantification of nicotinic acid and its analogues/derivates directly in the hypanthium of apple and pear blossoms. Analyses established the presence of nicotinic acid and nicotinamide, whereas no detectable amounts of 6-hydroxynicotinic acid and 2-hydroxynicotinic acid were observed. Mean nicotinic acid content in the pear hypanthium was found to be approximately 2 orders of magnitude higher than in the apple hypanthium, which may contribute to the differential susceptibility of these two host species to fire blight. Contents of nicotinamide were in contrast similar. Nicotinic acid can therefore be considered a relevant factor in the pathogen establishment in pear blossoms, whereas nicotinamide could cover a primary role in apple blossoms.

Bio-protective microbial agents from rhizosphere eco-systems trigger plant defense responses provide protection against sheath blight disease in rice (Oryza sativa L.).

PubMed

Singh, Udai B; Malviya, Deepti; Wasiullah; Singh, Shailendra; Pradhan, Jatindra K; Singh, Bhanu P; Roy, Manish; Imram, Mohd; Pathak, Neelam; Baisyal, B M; Rai, Jai P; Sarma, B K; Singh, Rajiv K; Sharma, P K; Kaur, Saman Deep; Manna, M C; Sharma, Sushil K; Sharma, Arun K

2016-11-01

Sheath blight of rice (Oryza sativa L.) caused by Rhizoctonia solani is a major disease and attempts are being made to develop microbe based technologies for biocontrol of this pathogen. However, the mechanisms of biocontrol are not fully understood and still require indepth study in the backdrop of emerging concepts in biological systems. The present investigation was aimed at deciphering the mechanisms of biocontrol of sheath blight of rice employing Pseudomonas fluorescens and Trichoderma harzianum as model agents for biocontrol. Initially 25, 5 and 5 strains of P. fluorescens, T. viride and T. harzianum, respectively, were screened for their biocontrol potential. Out of which, six strains with higher value of percent inhibition of fungal mycelium in dual plate assay were selected. The role of P. fluorescens, T. viride and T. harzianum were investigated in induction and bioaccumulation of natural antioxidants, defence-related biomolecules and other changes in plant which lead not only to growth promotion but also protection from pathogenic stress conditions in rice. The two most promising strains, P. fluorescens PF-08 and T. harzianum UBSTH-501 selected on the basis of in planta evaluation, when applied individually or in combination, significantly enhanced the accumulation of defence-related biomolecules, enzymes and exhibited biocontrol potential against R. solani. A modified/newly developed delivery system was applied for the first time in the experiments involving inoculation of plants with both bioagents, viz. P. fluorescens PF-08 and T. harzianum UBSTH-501. Results suggested that application of P. fluorescens PF-08 and T. harzianum UBSTH-501 alone or in combination, not only helps in control of the disease but also increases plant growth along with reduction in application of toxic chemical pesticides. Copyright © 2016 Elsevier GmbH. All rights reserved.

Proteomic characterization of the Rph15 barley resistance gene-mediated defence responses to leaf rust

PubMed Central

2012-01-01

Background Leaf rust, caused by the biotrophic fungal pathogen Puccinia hordei, is one of the most important foliar disease of barley (Hordeum vulgare) and represents a serious threat in many production regions of the world. The leaf rust resistance gene Rph15 is of outstanding interest for resistance breeding because it confers resistance to over 350 Puccinia hordei isolates collected from around the world. Molecular and biochemical mechanisms responsible for the Rph15 effectiveness are currently not investigated. The aim of the present work was to study the Rph15-based defence responses using a proteomic approach. Results Protein pattern changes in response to the leaf rust pathogen infection were investigated in two barley near isogenic lines (NILs), Bowman (leaf rust susceptible) and Bowman-Rph15 (leaf rust resistant), differing for the introgression of the leaf rust resistance gene Rph15. Two infection time points, 24 hours and four days post inoculation (dpi), were analysed. No statistically significant differences were identified at the early time point, while at 4 dpi eighteen protein spots were significantly up or down regulated with a fold-change equal or higher than two in response to pathogen infection. Almost all the pathogen-responsive proteins were identified in the Bowman-Rph15 resistant NIL. Protein spots were characterized by LC-MS/MS analysis and found to be involved in photosynthesis and energy metabolism, carbohydrate metabolism, protein degradation and defence. Proteomic data were complemented by transcriptional analysis of the respective genes. The identified proteins can be related to modulation of the photosynthetic apparatus components, re-direction of the metabolism to sustain defence responses and deployment of defence proteins. Conclusions The identification of leaf rust infection-modulated defence responses restricted to the resistant NIL support the hypothesis that basal defence responses of Bowman, but not the Rph15 resistance gene-based ones, are suppressed or delayed by pathogen effectors to levels below the detection power of the adopted proteomic approach. Additionally, Rph15-mediated resistance processes identified mainly resides on a modulation of primary metabolism, affecting photosyntesis and carbohydrate pool. PMID:23167439

The inheritance of resistance to bacterial leaf spot of lettuce caused by Xanthomonas campestris pv. vitians in three lettuce cultivars

USDA-ARS?s Scientific Manuscript database

Lettuce yields can be reduced by the disease bacterial leaf spot (BLS) caused by the pathogen Xanthomonas campestris pv. vitians (Xcv) and host resistance is the most feasible method to reduce disease losses. The cultivars La Brillante, Pavane, and Little Gem express an incompatible host-pathogen in...

Characterization of the common bean host and Pseudocercospora griseola the causative agent of angular leaf spot disease in Tanzania

USDA-ARS?s Scientific Manuscript database

Angular leaf spot (ALS) caused by the fungus Pseudocercospora griseola is one of the most important diseases of common bean in Tanzania. Breeding for resistance to this disease is complicated by the variable nature of the pathogen. In Tanzania no thorough analysis of the variability of this pathogen...

Fusarium graminearum and Its Interactions with Cereal Heads: Studies in the Proteomics Era

PubMed Central

Yang, Fen; Jacobsen, Susanne; Jørgensen, Hans J. L.; Collinge, David B.; Svensson, Birte; Finnie, Christine

2013-01-01

The ascomycete fungal pathogen Fusarium graminearum (teleomorph stage: Gibberella zeae) is the causal agent of Fusarium head blight in wheat and barley. This disease leads to significant losses of crop yield, and especially quality through the contamination by diverse fungal mycotoxins, which constitute a significant threat to the health of humans and animals. In recent years, high-throughput proteomics, aiming at identifying a broad spectrum of proteins with a potential role in the pathogenicity and host resistance, has become a very useful tool in plant-fungus interaction research. In this review, we describe the progress in proteomics applications toward a better understanding of F. graminearum pathogenesis, virulence, and host defense mechanisms. The contribution of proteomics to the development of crop protection strategies against this pathogen is also discussed briefly. PMID:23450732

Root-expressed maize lipoxygenase 3 negatively regulates induced systemic resistance to Colletotrichum graminicola in shoots

PubMed Central

Constantino, Nasie N.; Mastouri, Fatemeh; Damarwinasis, Ramadhika; Borrego, Eli J.; Moran-Diez, Maria E.; Kenerley, Charley M.; Gao, Xiquan; Kolomiets, Michael V.

2013-01-01

We have previously reported that disruption of a maize root-expressed 9-lipoxygenase (9-LOX) gene, ZmLOX3, results in dramatic increase in resistance to diverse leaf and stalk pathogens. Despite evident economic significance of these findings, the mechanism behind this increased resistance remained elusive. In this study, we found that increased resistance of the lox3-4 mutants is due to constitutive activation of induced systemic resistance (ISR) signaling. We showed that ZmLOX3 lacked expression in leaves in response to anthracnose leaf blight pathogen Colletotrichum graminicola, but was expressed constitutively in the roots, thus, prompting our hypothesis: the roots of lox3-4 mutants are the source of increased resistance in leaves. Supporting this hypothesis, treatment of wild-type plants (WT) with xylem sap of lox3-4 mutant induced resistance to C. graminicola to the levels comparable to those observed in lox3-4 mutant. Moreover, treating mutants with the sap collected from WT plants partially restored the susceptibility to C. graminicola. lox3-4 mutants showed primed defense responses upon infection, which included earlier and greater induction of defense-related PAL and GST genes compared to WT. In addition to the greater expression of the octadecanoid pathway genes, lox3-4 mutant responded earlier and with a greater accumulation of H2O2 in response to C. graminicola infection or treatment with alamethicin. These findings suggest that lox3-4 mutants display constitutive ISR-like signaling. In support of this idea, root colonization by Trichoderma virens strain GV29-8 induced the same level of disease resistance in WT as the treatment with the mutant sap, but had no additional resistance effect in lox3-4 mutant. While treatment with T. virens GV29 strongly and rapidly suppressed ZmLOX3 expression in hydroponically grown WT roots, T. virens Δsml mutant, which is deficient in ISR induction, was unable to suppress expression of ZmLOX3, thus, providing genetic evidence that SM1 function in ISR, at least in part, by suppressing host ZmLOX3 gene. This study and the genetic tools generated herein will allow the identification of the signals regulating the induction of resistance to aboveground attackers by beneficial soil microorganisms in the future. PMID:24391653

Two Cassava Basic Leucine Zipper (bZIP) Transcription Factors (MebZIP3 and MebZIP5) Confer Disease Resistance against Cassava Bacterial Blight.

PubMed

Li, Xiaolin; Fan, Shuhong; Hu, Wei; Liu, Guoyin; Wei, Yunxie; He, Chaozu; Shi, Haitao

2017-01-01

Basic domain-leucine zipper (bZIP) transcription factor, one type of conserved gene family, plays an important role in plant development and stress responses. Although 77 MebZIPs have been genome-wide identified in cassava, their in vivo roles remain unknown. In this study, we analyzed the expression pattern and the function of two MebZIPs ( MebZIP3 and MebZIP5 ) in response to pathogen infection. Gene expression analysis indicated that MebZIP3 and MebZIP5 were commonly regulated by flg22, Xanthomonas axonopodis pv. manihotis ( Xam ), salicylic acid (SA), and hydrogen peroxide (H 2 O 2 ). Subcellular localization analysis showed that MebZIP3 and MebZIP5 are specifically located in cell nucleus. Through overexpression in tobacco, we found that MebZIP3 and MebZIP5 conferred improved disease resistance against cassava bacterial blight, with more callose depositions. On the contrary, MebZIP3- and MebZIP5 -silenced plants by virus-induced gene silencing (VIGS) showed disease sensitive phenotype, lower transcript levels of defense-related genes and less callose depositions. Taken together, this study highlights the positive role of MebZIP3 and MebZIP5 in disease resistance against cassava bacterial blight for further utilization in genetic improvement of cassava disease resistance.

Protective role of biosynthesized silver nanoparticles against early blight disease in Solanum lycopersicum.

PubMed

Kumari, Madhuree; Pandey, Shipra; Bhattacharya, Arpita; Mishra, Aradhana; Nautiyal, C S

2017-12-01

Tomato suffers a huge loss every year because of early blight disease. This study focuses on efficient inhibition of Alternaria solani, the causative agent of early blight disease in tomato in vitro and in vivo. Foliar spray of 5 μg/mL of biosynthesized silver nanoparticles in A. solani infected plants resulted in significant increase of 32.58% in fresh weight and 23.52% in total chlorophyll content of tomato as compared to A. solani infected plants. A decrease of 48.57, 30, 39.59 and 28.57% was observed in fungal spore count, lipid peroxidation, proline content and superoxide dismutase respectively in infected tomato plants after treatment with synthesized silver nanoparticles as compared to A. solani infected plants. No significant variation in terms of soil pH, cultured population, carbon source utilization pattern and soil enzymes including dehydrogenase, urease, protenase and β-glucosidase was observed after foliar spray of nanoparticles. It was revealed that direct killing of pathogens, increased photosynthetic efficiencies, increased plant resistance and decrease in stress parameters and stress enzymes are the mechanisms employed by plants and nanoparticles simultaneously to combat the biotic stress. Biosynthesized silver nanoparticles bear the potential to revolutionize plant disease management, though the molecular aspects of increased resistance must be looked upon. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

[Association of phytoplasma with Bermuda grass white-leaf disease].

PubMed

Tan, Weijun; Chen, Yong; Zhang, Wu; Han, Chengchou; Tan, Zhiyuan; Zhang, Juming

2008-10-01

Bermuda grass white leaf is an important disease on Bermuda grass all over the world. The aim of this research is to identify the pathogen which leads to Bermuda grass white leaf occurring on the Chinese mainland. PCR amplification technique, sequence analysis and Southern hybridization were used. A 1.3 kb fragment was amplified by PCR phytoplasma universal primers and total DNA sample extracted from ill Bermuda grass as the amplified template. Sequence analysis of the amplified fragment indicated it clustered into Candidatus Phytoplasm Cynodontis. Southern hybridization analysis showed differential cingulums. The pathogen of Bermuda grass white leaf on the Chinese mainland contains phytoplasma, which provides a scientific basis for further identification, prevention and control of the disease.

Pre symptomatic detection of wheat leaf rust in the susceptible cv Skalmeje and the resistant cv Esket by means of UV laser-induced fluorescence.

PubMed

Bürling, K; Hunsche, M; Noga, G

2010-01-01

In modern agriculture there is a great demand for a rapid and objective screening method for stress resistance, because so far, the resistance of new cultivars is tested in time- and money consuming field experiments. Based on fluorescence ratios, and lifetime of fluorophores measured by fluorescence spectroscopy, we have postulated that an early discrimination of susceptible and resistant wheat cultivars to the leaf rust pathogen Puccinia triticina can be accomplished. As representative for leaf rust resistant and leaf rust susceptible wheat genotypes the cultivars Esket and Skalmeje, respectively, were chosen. Plants were grown under controlled environment conditions and inoculated with the leaf rust pathogen at the second-leaf-stage by single-droplet application. Fluorescence measurements were carried out from two to four days after inoculation (dai) by using a compact fibre-optic fluorescence spectrometer with nanosecond time-resolution. Experimental results indicated that UV laser-induced spectral characteristics as well as determination of fluorescence lifetime are suited to detect leaf rust two dai. For this purpose several ratios and wavelength can be considered. In general, the tested cultivars showed distinct responses to the pathogen development. In this context the ratio F451/F687 measured three dai and mean lifetimes at 500 nm and 530 nm are suited to differentiate the resistant Esket from the susceptible Skalmeje genotypes.

Genomic analyses of dominant U.S. clonal lineages of Phytophthora infestans reveals a shared common ancestry for clonal lineages US11 and US18 and a lack of recently shared ancestry among all other U.S. lineages

USDA-ARS?s Scientific Manuscript database

The populations of the potato and tomato late blight pathogen, Phytophthora infestans, in the US are well known for emerging repeatedly as novel clonal lineages. These successions of dominant clones have historically been named US1-US24, in order of appearance, since their first characterization usi...

The use of Proline (Prothioconazole) to control pitch canker, Rhizoctonia foliage blight, and Fusiform rust in forest seedling nurseries and efforts to acquire registration

Treesearch

Tom E. Starkey; Scott A. Enebak

2011-01-01

Laboratory, greenhouse, and field trials have shown Proline® to be efficacious against three fungal pathogens that cause damage and seedling mortality in forest seedling nurseries. Disease control using Proline® has been obtained at 365 ml/ha (5 fl oz/ac) for the control of fusiform rust (Cronartium quercuum f.sp. fusiforme) on loblolly pine (Pinus taeda) in both...

Analysis of DNA methylation related to rice adult plant resistance to bacterial blight based on methylation-sensitive AFLP (MSAP) analysis.

PubMed

Sha, A H; Lin, X H; Huang, J B; Zhang, D P

2005-07-01

DNA methylation is known to play an important role in the regulation of gene expression in eukaryotes. The rice cultivar Wase Aikoku 3 becomes resistant to the blight pathogen Xanthomonas oryzae pv. oryzae at the adult stage. Using methylation-sensitive amplified polymorphism (MSAP) analysis, we compared the patterns of cytosine methylation in seedlings and adult plants of the rice cultivar Wase Aikoku 3 that had been inoculated with the pathogen Xanthomonas oryzae pv. oryzae, subjected to mock inoculation or left untreated. In all, 2000 DNA fragments, each representing a recognition site cleaved by either or both of two isoschizomers, were amplified using 60 pairs of selective primers. A total of 380 sites were found to be methylated. Of these, 45 showed differential cytosine methylation among the seedlings and adult plants subjected to different treatments, and overall levels of methylation were higher in adult plants than in seedlings. All polymorphic fragments were sequenced, and six showed homology to genes that code for products of known function. Northern analysis of three fragments indicated that their expression varied with methylation pattern, with hypermethylation being correlated with repression of transcription, as expected. The results suggest that significant differences in cytosine methylation exist between seedlings and adult plants, and that hypermethylation or hypomethylation of specific genes may be involved in the development of adult plant resistance (APR) in rice plants.

RNAi as an emerging approach to control Fusarium head blight disease and mycotoxin contamination in cereals

PubMed Central

Machado, Ana Karla; Brown, Neil A; Urban, Martin; Kanyuka, Kostya

2017-01-01

Abstract Fusarium graminearum is a major fungal pathogen of cereals worldwide, causing seedling, stem base and floral diseases, including Fusarium head blight (FHB). In addition to yield and quality losses, FHB contaminates cereal grain with mycotoxins, including deoxynivalenol, which are harmful to human, animal and ecosystem health. Currently, FHB control is only partially effective due to several intractable problems. RNA interference (RNAi) is a natural mechanism that regulates gene expression. RNAi has been exploited in the development of new genomic tools that allow the targeted silencing of genes of interest in many eukaryotes. Host‐induced gene silencing (HIGS) is a transgenic technology used to silence fungal genes in planta during attempted infection and thereby reduces disease levels. HIGS relies on the host plant's ability to produce mobile small interfering RNA molecules, generated from long double‐stranded RNA, which are complementary to targeted fungal genes. These molecules are transferred from the plant to invading fungi via an uncharacterised mechanism, to cause gene silencing. Here, we describe recent advances in RNAi‐mediated control of plant pathogenic fungi, highlighting the key advantages and disadvantages. We then discuss the developments and implications of combining HIGS with other methods of disease control. © 2017 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry. PMID:28967180

DgcA, a diguanylate cyclase from Xanthomonas oryzae pv. oryzae regulates bacterial pathogenicity on rice

PubMed Central

Su, Jianmei; Zou, Xia; Huang, Liangbo; Bai, Tenglong; Liu, Shu; Yuan, Meng; Chou, Shan-Ho; He, Ya-Wen; Wang, Haihong; He, Jin

2016-01-01

Xanthomonas oryzae pv. oryzae (Xoo) is the causal agent of rice blight disease as well as a serious phytopathogen worldwide. It is also one of the model organisms for studying bacteria-plant interactions. Current progress in bacterial signal transduction pathways has identified cyclic di-GMP as a major second messenger molecule in controlling Xanthomonas pathogenicity. However, it still remains largely unclear how c-di-GMP regulates the secretion of bacterial virulence factors in Xoo. In this study, we focused on the important roles played by DgcA (XOO3988), one of our previously identified diguanylate cyclases in Xoo, through further investigating the phenotypes of several dgcA-related mutants, namely, the dgcA-knockout mutant ΔdgcA, the dgcA overexpression strain OdgcA, the dgcA complemented strain CdgcA and the wild-type strain. The results showed that dgcA negatively affected virulence, EPS production, bacterial autoaggregation and motility, but positively triggered biofilm formation via modulating the intracellular c-di-GMP levels. RNA-seq data further identified 349 differentially expressed genes controlled by DgcA, providing a foundation for a more solid understanding of the signal transduction pathways in Xoo. Collectively, the present study highlights DgcA as a major regulator of Xoo virulence, and can serve as a potential target for preventing rice blight diseases. PMID:27193392

Utilizing ERTS imagery to detect plant diseases and nutrient deficiencies, soil types and soil moisture levels

NASA Technical Reports Server (NTRS)

Parks, W. L.; Sewell, J. I.; Hilty, J. W.; Rennie, J. C. (Principal Investigator)

1974-01-01

The author has identified the following significant results. ERTS-1 imagery may be used to delineate soil associations. It does have the capacity to divide soils into groups such that their land use and management would be similar. It offers definite potential for making grass flood-plain, wetland, river shoreline, and land use change surveys. Production of volume strata and forest type from the two usable bands of ERTS-1 imagery were of questionable value. No imagery was received for evaluation during the time of year when maine dwarf mosaic virus and southern corn leaf blight were active.

The chestnut blight fungus for studies on virus/host and virus/virus interactions: from a natural to a model host.

PubMed

Eusebio-Cope, Ana; Sun, Liying; Tanaka, Toru; Chiba, Sotaro; Kasahara, Shin; Suzuki, Nobuhiro

2015-03-01

The chestnut blight fungus, Cryphonectria parasitica, is an important plant pathogenic ascomycete. The fungus hosts a wide range of viruses and now has been established as a model filamentous fungus for studying virus/host and virus/virus interactions. This is based on the development of methods for artificial virus introduction and elimination, host genome manipulability, available host genome sequence with annotations, host mutant strains, and molecular tools. Molecular tools include sub-cellular distribution markers, gene expression reporters, and vectors with regulatable promoters that have been long available for unicellular organisms, cultured cells, individuals of animals and plants, and certain filamentous fungi. A comparison with other filamentous fungi such as Neurospora crassa has been made to establish clear advantages and disadvantages of C. parasitica as a virus host. In addition, a few recent studies on RNA silencing vs. viruses in this fungus are introduced. Copyright © 2014 Elsevier Inc. All rights reserved.

Herbivores and pathogens on Alnus viridis subsp. fruticosa in interior Alaska: effects of leaf, tree, and neighbour characteristics on damage levels

Treesearch

Christa P.H. Mulder; Bitty A. Roy; Sabine Gusewell

2008-01-01

Parasite damage strongly affects dynamics of boreal forests. Damage levels may be affected by climate change, either directly or indirectly through changes in properties of host trees. We examined how herbivore and pathogen damage in Alnus viridis subsp. fruticosa (Rupr.) Nym. depend on leaf morphology and chemistry, tree size...

Conventional and Real-Time PCRs for Detection of Erwinia piriflorinigrans Allow Its Distinction from the Fire Blight Pathogen, Erwinia amylovora

PubMed Central

Barbé, Silvia; Bertolini, Edson; Roselló, Montserrat; Llop, Pablo

2014-01-01

Erwinia piriflorinigrans is a new pathogenic species of the bacterial genus Erwinia that has been described recently in Spain. Accurate detection and identification of E. piriflorinigrans are challenging because its symptoms on pear blossoms are similar to those caused by Erwinia amylovora, the causal agent of fire blight. Moreover, these two species share phenotypic and molecular characteristics. Two specific and sensitive conventional and real-time PCR protocols were developed to identify and detect E. piriflorinigrans and to differentiate it from E. amylovora and other species of this genus. These protocols were based on sequences from plasmid pEPIR37, which is present in all strains of E. piriflorinigrans analyzed. After the stability of the plasmid was demonstrated, the specificities of the protocols were confirmed by the amplification of all E. piriflorinigrans strains tested, whereas 304 closely related pathogenic and nonpathogenic Erwinia strains and microbiota from pear trees were not amplified. In sensitivity assays, 103 cells/ml extract were detected in spiked plant material by conventional or real-time PCR, and 102 cells/ml were detected in DNA extracted from spiked plant material by real-time PCR. The protocols developed here succeeded in detecting E. piriflorinigrans in 102 out of 564 symptomatic and asymptomatic naturally infected pear samples (flowers, cortex stem tissue, leaves, shoots, and fruitlets), in necrotic Pyracantha sp. blossoms, and in necrotic pear and apple tissues infected with both E. amylovora and E. piriflorinigrans. Therefore, these new tools can be used in epidemiological studies that will enhance our understanding of the life cycle of E. piriflorinigrans in different hosts and plant tissues and its interaction with E. amylovora. PMID:24509928

Conventional and real-time PCRs for detection of Erwinia piriflorinigrans allow its distinction from the fire blight pathogen, Erwinia amylovora.

PubMed

Barbé, Silvia; Bertolini, Edson; Roselló, Montserrat; Llop, Pablo; López, María M

2014-04-01

Erwinia piriflorinigrans is a new pathogenic species of the bacterial genus Erwinia that has been described recently in Spain. Accurate detection and identification of E. piriflorinigrans are challenging because its symptoms on pear blossoms are similar to those caused by Erwinia amylovora, the causal agent of fire blight. Moreover, these two species share phenotypic and molecular characteristics. Two specific and sensitive conventional and real-time PCR protocols were developed to identify and detect E. piriflorinigrans and to differentiate it from E. amylovora and other species of this genus. These protocols were based on sequences from plasmid pEPIR37, which is present in all strains of E. piriflorinigrans analyzed. After the stability of the plasmid was demonstrated, the specificities of the protocols were confirmed by the amplification of all E. piriflorinigrans strains tested, whereas 304 closely related pathogenic and nonpathogenic Erwinia strains and microbiota from pear trees were not amplified. In sensitivity assays, 10(3) cells/ml extract were detected in spiked plant material by conventional or real-time PCR, and 10(2) cells/ml were detected in DNA extracted from spiked plant material by real-time PCR. The protocols developed here succeeded in detecting E. piriflorinigrans in 102 out of 564 symptomatic and asymptomatic naturally infected pear samples (flowers, cortex stem tissue, leaves, shoots, and fruitlets), in necrotic Pyracantha sp. blossoms, and in necrotic pear and apple tissues infected with both E. amylovora and E. piriflorinigrans. Therefore, these new tools can be used in epidemiological studies that will enhance our understanding of the life cycle of E. piriflorinigrans in different hosts and plant tissues and its interaction with E. amylovora.

More Cercospora Species Infect Soybeans across the Americas than Meets the Eye

PubMed Central

Soares, Ana Paula Gomes; Guillin, Eduardo A.; Borges, Leandro Luiz; da Silva, Amanda C. T.; de Almeida, Álvaro M. R.; Grijalba, Pablo E.; Gottlieb, Alexandra M.; Bluhm, Burton H.; de Oliveira, Luiz Orlando

2015-01-01

Diseases of soybean caused by Cercospora spp. are endemic throughout the world’s soybean production regions. Species diversity in the genus Cercospora has been underestimated due to overdependence on morphological characteristics, symptoms, and host associations. Currently, only two species (Cercospora kikuchii and C. sojina) are recognized to infect soybean; C. kikuchii causes Cercospora leaf blight (CLB) and purple seed stain (PSS), whereas C. sojina causes frogeye leaf spot. To assess cryptic speciation among pathogens causing CLB and PSS, phylogenetic and phylogeographic analyses were performed with isolates from the top three soybean producing countries (USA, Brazil, and Argentina; collectively accounting for ~80% of global production). Eight nuclear genes and one mitochondrial gene were partially sequenced and analyzed. Additionally, amino acid substitutions conferring fungicide resistance were surveyed, and the production of cercosporin (a polyketide toxin produced by many Cercospora spp.) was assessed. From these analyses, the long-held assumption of C. kikuchii as the single causal agent of CLB and PSS was rejected experimentally. Four cercosporin-producing lineages were uncovered with origins (about 1 Mya) predicted to predate agriculture. Some of the Cercospora spp. newly associated with CLB and PSS appear to represent undescribed species; others were not previously reported to infect soybeans. Lineage 1, which contained the ex-type strain of C. kikuchii, was monophyletic and occurred in Argentina and Brazil. In contrast, lineages 2 and 3 were polyphyletic and contained wide-host range species complexes. Lineage 4 was monophyletic, thrived in Argentina and the USA, and included the generalist Cercospora cf. flagellaris. Interlineage recombination was detected, along with a high frequency of mutations linked to fungicide resistance in lineages 2 and 3. These findings point to cryptic Cercospora species as underappreciated global considerations for soybean production and phytosanitary vigilance, and urge a reassessment of host-specificity as a diagnostic tool for Cercospora. PMID:26252018

More Cercospora Species Infect Soybeans across the Americas than Meets the Eye.

PubMed

Soares, Ana Paula Gomes; Guillin, Eduardo A; Borges, Leandro Luiz; Silva, Amanda C T da; Almeida, Álvaro M R de; Grijalba, Pablo E; Gottlieb, Alexandra M; Bluhm, Burton H; Oliveira, Luiz Orlando de

2015-01-01

Diseases of soybean caused by Cercospora spp. are endemic throughout the world's soybean production regions. Species diversity in the genus Cercospora has been underestimated due to overdependence on morphological characteristics, symptoms, and host associations. Currently, only two species (Cercospora kikuchii and C. sojina) are recognized to infect soybean; C. kikuchii causes Cercospora leaf blight (CLB) and purple seed stain (PSS), whereas C. sojina causes frogeye leaf spot. To assess cryptic speciation among pathogens causing CLB and PSS, phylogenetic and phylogeographic analyses were performed with isolates from the top three soybean producing countries (USA, Brazil, and Argentina; collectively accounting for ~80% of global production). Eight nuclear genes and one mitochondrial gene were partially sequenced and analyzed. Additionally, amino acid substitutions conferring fungicide resistance were surveyed, and the production of cercosporin (a polyketide toxin produced by many Cercospora spp.) was assessed. From these analyses, the long-held assumption of C. kikuchii as the single causal agent of CLB and PSS was rejected experimentally. Four cercosporin-producing lineages were uncovered with origins (about 1 Mya) predicted to predate agriculture. Some of the Cercospora spp. newly associated with CLB and PSS appear to represent undescribed species; others were not previously reported to infect soybeans. Lineage 1, which contained the ex-type strain of C. kikuchii, was monophyletic and occurred in Argentina and Brazil. In contrast, lineages 2 and 3 were polyphyletic and contained wide-host range species complexes. Lineage 4 was monophyletic, thrived in Argentina and the USA, and included the generalist Cercospora cf. flagellaris. Interlineage recombination was detected, along with a high frequency of mutations linked to fungicide resistance in lineages 2 and 3. These findings point to cryptic Cercospora species as underappreciated global considerations for soybean production and phytosanitary vigilance, and urge a reassessment of host-specificity as a diagnostic tool for Cercospora.

Studies on the Control of Ascochyta Blight in Field Peas (Pisum sativum L.) Caused by Ascochyta pinodes in Zhejiang Province, China

PubMed Central

Liu, Na; Xu, Shengchun; Yao, Xiefeng; Zhang, Guwen; Mao, Weihua; Hu, Qizan; Feng, Zhijuan; Gong, Yaming

2016-01-01

Ascochyta blight, an infection caused by a complex of Ascochyta pinodes, Ascochyta pinodella, Ascochyta pisi, and/or Phoma koolunga, is a destructive disease in many field peas (Pisum sativum L.)-growing regions, and it causes significant losses in grain yield. To understand the composition of fungi associated with this disease in Zhejiang Province, China, a total of 65 single-pycnidiospore fungal isolates were obtained from diseased pea samples collected from 5 locations in this region. These isolates were identified as Ascochyta pinodes by molecular techniques and their morphological and physiological characteristics. The mycelia of ZJ-1 could penetrate pea leaves across the stomas, and formed specific penetration structures and directly pierced leaves. The resistance level of 23 available pea cultivars was tested against their representative isolate A. pinodes ZJ-1 using the excised leaf-assay technique. The ZJ-1 mycelia could penetrate the leaves of all tested cultivars, and they developed typical symptoms, which suggested that all tested cultivars were susceptible to the fungus. Chemical fungicides and biological control agents were screened for management of this disease, and their efficacies were further determined. Most of the tested fungicides (11 out of 14) showed high activity toward ZJ-1 with EC50 < 5 μg/mL. Moreover, fungicides, including tebuconazole, boscalid, iprodione, carbendazim, and fludioxonil, displayed more than 80% disease control efficacy under the recorded conditions. Three biocontrol strains of Bacillus sp. and one of Pantoea agglomerans were isolated from pea-related niches and significantly reduced the severity of disease under greenhouse and field conditions. To our knowledge, this is the first study on ascochyta blight in field peas, and results presented here will be useful for controlling the disease in this area. PMID:27148177

Development of somatic hybrids Solanum × michoacanum Bitter. (Rydb.) (+) S. tuberosum L. and autofused 4x S. × michoacanum plants as potential sources of late blight resistance for potato breeding.

PubMed

Smyda, P; Jakuczun, H; Dębski, K; Sliwka, J; Thieme, R; Nachtigall, M; Wasilewicz-Flis, I; Zimnoch-Guzowska, E

2013-08-01

Phytophthora infestans resistant somatic hybrids of S. × michoacanum (+) S. tuberosum and autofused 4 x S. × michoacanum were obtained. Our material is promising to introgress resistance from S. × michoacanum into cultivated potato background. Solanum × michoacanum (Bitter.) Rydb. (mch) is a wild diploid (2n = 2x = 24) potato species derived from spontaneous cross of S. bulbocastanum and S. pinnatisectum. This hybrid is a 1 EBN (endosperm balance number) species and can cross effectively only with other 1 EBN species. Plants of mch are resistant to Phytophthora infestans (Mont) de Bary. To introgress late blight resistance genes from mch into S. tuberosum (tbr), genepool somatic hybridization between mch and susceptible diploid potato clones (2n = 2x = 24) or potato cultivar Rywal (2n = 4x = 48) was performed. In total 18,775 calli were obtained from postfusion products from which 1,482 formed shoots. The Simple Sequence Repeat (SSR), Cleaved Amplified Polymorphic Sequences (CAPS) and Random Amplified Polymorphic DNA (RAPD) analyses confirmed hybrid nature of 228 plants and 116 autofused 4x mch. After evaluation of morphological features, flowering, pollen stainability, tuberization and ploidy level, 118 somatic hybrids and 116 autofused 4x mch were tested for late blight resistance using the detached leaf assay. After two seasons of testing three somatic hybrids and 109 4x mch were resistant. Resistant forms have adequate pollen stainability for use in crossing programme and are a promising material useful for introgression resistance from mch into the cultivated potato background.

Lactoferrin-derived resistance against plant pathogens in transgenic plants.

PubMed

Lakshman, Dilip K; Natarajan, Savithiry; Mandal, Sudhamoy; Mitra, Amitava

2013-12-04

Lactoferrin (LF) is a ubiquitous cationic iron-binding milk glycoprotein that contributes to nutrition and exerts a broad-spectrum primary defense against bacteria, fungi, protozoa, and viruses in mammals. These qualities make lactoferrin protein and its antimicrobial motifs highly desirable candidates to be incorporated in plants to impart broad-based resistance against plant pathogens or to economically produce them in bulk quantities for pharmaceutical and nutritional purposes. This study introduced bovine LF (BLF) gene into tobacco ( Nicotiana tabacum var. Xanthi), Arabidopsis ( A. thaliana ) and wheat ( Triticum aestivum ) via Agrobacterium -mediated plant transformation. Transgenic plants or detached leaves exhibited high levels of resistance against the damping-off causing fungal pathogen Rhizoctonia solani and the head blight causing fungal pathogen Fusarium graminearum . LF also imparted resistance to tomato plants against a bacterial pathogen, Ralstonia solanacearum . Similarly, other researchers demonstrated expression of LF and LF-mediated high-quality resistance to several other aggressive fungal and bacterial plant pathogens in transgenic plants and against viral pathogens by foliar applications of LF or its derivatives. Taken together, these studies demonstrated the effectiveness of LF for improving crop quality and its biopharming potentials for pharmaceautical and nutritional applications.

RNA-Seq analysis of resistant and susceptible sub-tropical maize lines reveals a role for kauralexins in resistance to grey leaf spot disease, caused by Cercospora zeina

USDA-ARS?s Scientific Manuscript database

Cercospora zeina is a foliar pathogen responsible for maize grey leaf spot in southern Africa that negatively impacts maize production. Plants use a variety of chemical and structural mechanisms to defend themselves against invading pathogens such as C. zeina, including the production of secondary m...

Assessing Quantitative Resistance against Leptosphaeria maculans (Phoma Stem Canker) in Brassica napus (Oilseed Rape) in Young Plants

PubMed Central

Huang, Yong-Ju; Qi, Aiming; King, Graham J.; Fitt, Bruce D. L.

2014-01-01

Quantitative resistance against Leptosphaeria maculans in Brassica napus is difficult to assess in young plants due to the long period of symptomless growth of the pathogen from the appearance of leaf lesions to the appearance of canker symptoms on the stem. By using doubled haploid (DH) lines A30 (susceptible) and C119 (with quantitative resistance), quantitative resistance against L. maculans was assessed in young plants in controlled environments at two stages: stage 1, growth of the pathogen along leaf veins/petioles towards the stem by leaf lamina inoculation; stage 2, growth in stem tissues to produce stem canker symptoms by leaf petiole inoculation. Two types of inoculum (ascospores; conidia) and three assessment methods (extent of visible necrosis; symptomless pathogen growth visualised using the GFP reporter gene; amount of pathogen DNA quantified by PCR) were used. In stage 1 assessments, significant differences were observed between lines A30 and C119 in area of leaf lesions, distance grown along veins/petioles assessed by visible necrosis or by viewing GFP and amount of L. maculans DNA in leaf petioles. In stage 2 assessments, significant differences were observed between lines A30 and C119 in severity of stem canker and amount of L. maculans DNA in stem tissues. GFP-labelled L. maculans spread more quickly from the stem cortex to the stem pith in A30 than in C119. Stem canker symptoms were produced more rapidly by using ascospore inoculum than by using conidial inoculum. These results suggest that quantitative resistance against L. maculans in B. napus can be assessed in young plants in controlled conditions. Development of methods to phenotype quantitative resistance against plant pathogens in young plants in controlled environments will help identification of stable quantitative resistance for control of crop diseases. PMID:24454767

Is There a Relation between the Microscopic Leaf Morphology and the Association of Salmonella and Escherichia coli O157:H7 with Iceberg Lettuce Leaves?

PubMed

VAN der Linden, Inge; Eriksson, Markus; Uyttendaele, Mieke; Devlieghere, Frank

2016-10-01

To prevent contamination of fresh produce with enteric pathogens, more insight into mechanisms that may influence the association of these pathogens with fresh produce is needed. In this study, Escherichia coli O157:H7 and Salmonella were chosen as model pathogens, and fresh cut iceberg lettuce was chosen as a model fresh produce type. The morphological structure of iceberg lettuce leaves (stomatal density and length of cell margins per leaf area) was quantified by means of leaf peels and light microscopy of leaves at different stages of development (outer, middle, and inner leaves of the crop) on both leaf sides (abaxial and adxial) and in three leaf regions (top, center, and bottom). The morphology of the top region of the leaves was distinctly different from that of the center and base, with a significantly higher stomatal density (up to five times more stomata), different cell shape, and longer cell margins (two to three times longer). Morphological differences between the same regions of the leaves at different stages of development were smaller or nonsignificant. An attachment assay with two attenuated E. coli O157:H7 strains (84-24h11-GFP and BRMSID 188 GFP) and two Salmonella strains (serovars Thompson and Typhimurium) was performed on different regions of the middle leaves. Our results confirmed earlier reports that these pathogens have a higher affinity for the base of the lettuce leaf than the top. Differences of up to 2.12 log CFU/g were seen ( E. coli O157:H7 86-24h11-GFP). Intermediate attachment occurred in the central region. The higher incidence of preferential bacterial attachment sites such as stomata and cell margins or grooves could not explain the differences observed in the association of the tested pathogens with different regions of iceberg lettuce leaves.

Comparison of two possible routes of pathogen contamination of spinach leaves in a hydroponic cultivation system.

PubMed

Koseki, Shigenobu; Mizuno, Yasuko; Yamamoto, Kazutaka

2011-09-01

The route of pathogen contamination (from roots versus from leaves) of spinach leaves was investigated with a hydroponic cultivation system. Three major bacterial pathogens, Escherichia coli O157:H7, Salmonella, and Listeria monocytogenes, were inoculated into the hydroponic solution, in which the spinach was grown to give concentrations of 10⁶ and 10³ CFU/ml. In parallel, the pathogens were inoculated onto the growing leaf surface by pipetting, to give concentrations of 10⁶ and 10³ CFU per leaf. Although contamination was observed at a high rate through the root system by the higher inoculum (10⁶ CFU) for all the pathogens tested, the contamination was rare when the lower inoculum (10³ CFU) was applied. In contrast, contamination through the leaf occurred at a very low rate, even when the inoculum level was high. For all the pathogens tested in the present study, the probability of contamination was promoted through the roots and with higher inoculum levels. The probability of contamination was analyzed with logistic regression. The logistic regression model showed that the odds ratio of contamination from the roots versus from the leaves was 6.93, which suggested that the risk of contamination from the roots was 6.93 times higher than the risk of contamination from the leaves. In addition, the risk of contamination by L. monocytogenes was about 0.3 times that of Salmonella enterica subsp. enterica serovars Typhimurium and Enteritidis and E. coli O157:H7. The results of the present study indicate that the principal route of pathogen contamination of growing spinach leaves in a hydroponic system is from the plant's roots, rather than from leaf contamination itself.

First Report of Sclerotium Rot on Cymbidium Orchids Caused by Sclerotium rolfsii in Korea

PubMed Central

Lee, Seong-Chan; Lee, Jung-Sup; Soh, Jae-Woo; Kim, Su

2012-01-01

Sclerotium rot was found on Cymbidium orchids at Seosan-si, Chungcheongnam-do, Korea, in July, 2010. Symptoms occurred on low leaves, which turned yellowish, after which the entire plant wilted. Severely infected plants were blighted and eventually died. White mycelial mats and sclerotia appeared on pseudobulbs. Based on the mycological characteristics and pathogenicity, the causal fungus was identified as Sclerotium rolfsii. This is the first report of new Sclerotium rot on Cymbidium spp. caused by S. rolfsii in Korea. PMID:23323053

Fluorescent Staining of Tea Pathogenic Fungi in Tea Leaves Using Fluorescein-labeled Lectin

NASA Astrophysics Data System (ADS)

Yamada, Kengo; Yoshida, Katsuyuki; Sonoda, Ryoichi

Fluorochrome-labeled lectin, fluorescein conjugated wheat germ agglutinin (F-WGA) was applied to stain tea pathogenic fungi in tea leaf tissue. Infected leaves were fixed and decolorized with a mixture of ethanol and acetic acid, and cleared with 10% KOH for whole mount before staining with F-WGA. Hyphae of Pestalotiopsis longiseta, Pseudocercospora ocellata, Botrytis cinerea and Colletotrichum theae-sinensis fluoresced brightly in whole mount and sectioned samples of infected leaf tissue. In browned tissue, hyphae did not fluoresce frequently in whole mount sample. Autofluorescence of leaf tissue was strong in browned tissue of sections, it was removed by 10% KOH treatment before staining. Penetration hyphae of C. theae-sinensis in cell wall of trichome and hyphae in basal part of trichome did not fluoresced frequently. In whole mount samples of tea leaf infected with Exobasidium vexans and E. reticulatum, hymenia appeared on leaf surface fluoresced, but hyphae in leaf tissue did not fluoresce. In sectioned samples, hyphae fluoresced brightly when sections were treated with 10% KOH before staining.

Effects of early and late harvest on agronomic performance and stability of late blight resistant (R-gene free) potato genotypes

USDA-ARS?s Scientific Manuscript database

To assess the effectiveness of genotype resistance to potato late blight, foliar blight development, area under disease progress curves (AUDPC) and tuber blight were quantified. Late blight resistant potato genotypes (R-gene free) were assessed for yield performance and stability at early (90 days) ...

Genetics and breeding of bacterial leaf spot resistance

USDA-ARS?s Scientific Manuscript database

Bacterial leaf spot (BLS) caused by the pathogen Xanthomonas campestris pv. vitians (Xcv) is a globally important disease of whole head and baby leaf lettuce that reduces crop yield and quality. Host resistance is the most feasible method to reduce disease losses. Screening Lactuca accessions has id...

A transcription activator-like effector from Xanthomonas oryzae pv. oryzicola elicits dose-dependent resistance in rice.

PubMed

Hummel, Aaron W; Wilkins, Katherine E; Wang, Li; Cernadas, R Andres; Bogdanove, Adam J

2017-01-01

Xanthomonas spp. reduce crop yields and quality worldwide. During infection of their plant hosts, many strains secrete transcription activator-like (TAL) effectors, which enter the host cell nucleus and activate specific corresponding host genes at effector binding elements (EBEs) in the promoter. TAL effectors may contribute to disease by activating the expression of susceptibility genes or trigger resistance associated with the hypersensitive reaction (HR) by activating an executor resistance (R) gene. The rice bacterial leaf streak pathogen X. oryzae pv. oryzicola (Xoc) is known to suppress host resistance, and no host R gene has been identified against it, despite considerable effort. To further investigate Xoc suppression of host resistance, we conducted a screen of effectors from BLS256 and identified Tal2a as an HR elicitor in rice when delivered heterologously by a strain of the closely related rice bacterial blight pathogen X. oryzae pv. oryzae (Xoo) or by the soybean pathogen X. axonopodis pv. glycines. The HR required the Tal2a activation domain, suggesting an executor R gene. Tal2a activity was differentially distributed among geographically diverse Xoc isolates, being largely conserved among Asian isolates. We identified four genes induced by Tal2a in next-generation RNA sequencing experiments and confirmed them using quantitative real-time reverse transcription-polymerase chain reaction (qPCR). However, neither individual nor collective activation of these genes by designer TAL effectors resulted in HR. A tal2a knockout mutant of BLS256 showed virulence comparable with the wild-type, but plasmid-based overexpression of tal2a at different levels in the wild-type reduced virulence in a directly corresponding way. Overall, the results reveal that host resistance suppression by Xoc plays a critical role in pathogenesis. Further, the dose-dependent avirulence activity of Tal2a and the apparent lack of a single canonical target that accounts for HR point to a novel, activation domain-dependent mode of action, which might involve, for example, a non-coding gene or a specific pattern of activation across multiple targets. © 2016 BSPP and John Wiley & Sons Ltd.

De Novo Assembled Wheat Transcriptomes Delineate Differentially Expressed Host Genes in Response to Leaf Rust Infection.

PubMed

Chandra, Saket; Singh, Dharmendra; Pathak, Jyoti; Kumari, Supriya; Kumar, Manish; Poddar, Raju; Balyan, Harindra Singh; Gupta, Puspendra Kumar; Prabhu, Kumble Vinod; Mukhopadhyay, Kunal

2016-01-01

Pathogens like Puccinia triticina, the causal organism for leaf rust, extensively damages wheat production. The interaction at molecular level between wheat and the pathogen is complex and less explored. The pathogen induced response was characterized using mock- or pathogen inoculated near-isogenic wheat lines (with or without seedling leaf rust resistance gene Lr28). Four Serial Analysis of Gene Expression libraries were prepared from mock- and pathogen inoculated plants and were subjected to Sequencing by Oligonucleotide Ligation and Detection, which generated a total of 165,767,777 reads, each 35 bases long. The reads were processed and multiple k-mers were attempted for de novo transcript assembly; 22 k-mers showed the best results. Altogether 21,345 contigs were generated and functionally characterized by gene ontology annotation, mining for transcription factors and resistance genes. Expression analysis among the four libraries showed extensive alterations in the transcriptome in response to pathogen infection, reflecting reorganizations in major biological processes and metabolic pathways. Role of auxin in determining pathogenesis in susceptible and resistant lines were imperative. The qPCR expression study of four LRR-RLK (Leucine-rich repeat receptor-like protein kinases) genes showed higher expression at 24 hrs after inoculation with pathogen. In summary, the conceptual model of induced resistance in wheat contributes insights on defense responses and imparts knowledge of Puccinia triticina-induced defense transcripts in wheat plants.

De Novo Assembled Wheat Transcriptomes Delineate Differentially Expressed Host Genes in Response to Leaf Rust Infection

PubMed Central

Pathak, Jyoti; Kumari, Supriya; Kumar, Manish; Poddar, Raju; Balyan, Harindra Singh; Gupta, Puspendra Kumar; Prabhu, Kumble Vinod; Mukhopadhyay, Kunal

2016-01-01

Pathogens like Puccinia triticina, the causal organism for leaf rust, extensively damages wheat production. The interaction at molecular level between wheat and the pathogen is complex and less explored. The pathogen induced response was characterized using mock- or pathogen inoculated near-isogenic wheat lines (with or without seedling leaf rust resistance gene Lr28). Four Serial Analysis of Gene Expression libraries were prepared from mock- and pathogen inoculated plants and were subjected to Sequencing by Oligonucleotide Ligation and Detection, which generated a total of 165,767,777 reads, each 35 bases long. The reads were processed and multiple k-mers were attempted for de novo transcript assembly; 22 k-mers showed the best results. Altogether 21,345 contigs were generated and functionally characterized by gene ontology annotation, mining for transcription factors and resistance genes. Expression analysis among the four libraries showed extensive alterations in the transcriptome in response to pathogen infection, reflecting reorganizations in major biological processes and metabolic pathways. Role of auxin in determining pathogenesis in susceptible and resistant lines were imperative. The qPCR expression study of four LRR-RLK (Leucine-rich repeat receptor-like protein kinases) genes showed higher expression at 24 hrs after inoculation with pathogen. In summary, the conceptual model of induced resistance in wheat contributes insights on defense responses and imparts knowledge of Puccinia triticina-induced defense transcripts in wheat plants. PMID:26840746

Draft Genome Sequence of Cercospora arachidicola, Cause of Early Leaf Spot in Peanut

USDA-ARS?s Scientific Manuscript database

Cercospora arachidicola and Cercosporidium personatum, causal agents of early and late leaf spot, respectively, are important fungal pathogens of peanut. Leaf spot disease is a major contributor to the economic losses experienced by peanut farmers and the industry. Though peanut germplasms with so...

Conjunctively screening of biocontrol agents (BCAs) against fusarium root rot and fusarium head blight caused by Fusarium graminearum.

PubMed

Wang, Lu-Yao; Xie, Yue-Shen; Cui, Yuan-Yu; Xu, Jianjun; He, Wei; Chen, Huai-Gu; Guo, Jian-Hua

2015-08-01

Fusarium root-rot and fusarium head blight are plant diseases caused by Fusarium sp. in different growth periods of wheat, bring heavy losses to crop production in China. This research is aiming to screen biocontrol agents conjunctively for controlling these two diseases at the same time, as well as evaluate our previous BCAs (Biological Control Agents) screening strategies in more complex situation, considering biocontrol is well concerned as an environmental-friendly plant disease controlling method. Totally 966 bacterial isolates were screened from different parts of wheat tissues, of which potential biocontrol values were detected according to their abilities in antagonism inhibition and secreting extracellular hydrolytic enzyme. Biocontrol tests against fusarium root rot and fusarium head blight were carried out on 37 bacterial isolates with potential biocontrol capacity after pre-selection through ARDRA- and BOX-PCR analysis on strains with high assessment points. We acquired 10 BCAs with obvious biocontrol efficacy (more than 40%) in greenhouse and field tests. Pseudomonas fluorescens LY1-8 performed well in both two tests (biocontrol efficacy: 44.62% and 58.31%), respectively. Overall, correlation coefficient is 0.720 between assessment values of 37 tested BCA strains and their biocontrol efficacy in trails against fusarium root rot; correlation coefficient is 0.806 between their assessment values and biocontrol efficacy in trails against fusarium head blight. We acquired 10 well-performed potential BCAs, especially P. fluorescens LY1-8 displayed good biocontrol capacity against two different diseases on wheat. Biocontrol efficacies results in both greenhouse and field tests showed high positive correlation with assessment values (0.720 and 0.806), suggesting that the BCAs screening and assessing strategy previously developed in our lab is also adaptable for conjunctively screening BCAs for controlling both root and shoot diseases on wheat caused by same fungal pathogen. Copyright © 2015 Elsevier GmbH. All rights reserved.

Binding of the host-specific toxins from Helminthosporium maydis race T and Phyllosticta maydis to mitochondria isolated from Zea mays

DOE Office of Scientific and Technical Information (OSTI.GOV)

Frantzen, K.A.

1985-01-01

Helminthosphorium maydis race I and Phyllosticta maydis, the causal agents of southern and yellow corn leaf blights, respectively, produce host-specific toxins. The toxic specificity of these natural products is identical to the host-specificity of the pathogens for certain varieties of corn. Susceptible genotypes carry the Texas type of cytoplasmic male sterility. Isolated mitochondria from susceptible plant species are highly sensitive to these toxins, whereas other plant species, including resistant corn varieties, and their mitochondria are not. The mitochondrion may be the primary cellular site of action for these toxins. The toxins from H. maydis and P. maydis were tritiated bymore » reduction with borotritide salts. The labeled products had a high specific activity (3.8 to 8 Ci/mmole), high biological activity, and specificity identical to that of the native toxins. A filtration binding assay was developed to investigate the binding characteristics of these labeled toxins to isolated mitochondria. Mitochondria isolated from both cytoplasmic male sterile (Texas) and normal corn demonstrated similar binding characteristics including ligand displaceable binding with both labeled toxins. Ligand displaceable binding was also detectable in mitochondria from soybeans, a nonhost plant for these fungi. The ability to displace the bound labeled toxins was generally correlated with the biological activity of the competing toxin. The results of this study suggest that a receptor site hypothesis for the mode of action of these toxins may not be valid.« less

Microbial symbionts affect Pisum sativum proteome and metabolome under Didymella pinodes infection.

PubMed

Desalegn, G; Turetschek, R; Kaul, H-P; Wienkoop, S

2016-06-30

The long cultivation of field pea led to an enormous diversity which, however, seems to hold just little resistance against the ascochyta blight disease complex. The potential of below ground microbial symbiosis to prime the immune system of Pisum for an upcoming pathogen attack has hitherto received little attention. This study investigates the effect of beneficial microbes on the leaf proteome and metabolome as well as phenotype characteristics of plants in various symbiont interactions (mycorrhiza, rhizobia, co-inoculation, non-symbiotic) after infestation by Didymella pinodes. In healthy plants, mycorrhiza and rhizobia induced changes in RNA metabolism and protein synthesis. Furthermore, metal handling and ROS dampening was affected in all mycorrhiza treatments. The co-inoculation caused the synthesis of stress related proteins with concomitant adjustment of proteins involved in lipid biosynthesis. The plant's disease infection response included hormonal adjustment, ROS scavenging as well as synthesis of proteins related to secondary metabolism. The regulation of the TCA, amino acid and secondary metabolism including the pisatin pathway, was most pronounced in rhizobia associated plants which had the lowest infection rate and the slowest disease progression. A most comprehensive study of the Pisum sativum proteome and metabolome infection response to Didymella pinodes is provided. Several distinct patterns of microbial symbioses on the plant metabolism are presented for the first time. Upon D. pinodes infection, rhizobial symbiosis revealed induced systemic resistance e.g. by an enhanced level of proteins involved in pisatin biosynthesis. Copyright © 2016 The Authors. Published by Elsevier B.V. All rights reserved.

Isolation, characterization and antifungal activity of very long chain alkane derivatives from Cinnamomum obtusifolium, Elaeocarpus lanceifolius and Baccaurea sapida

NASA Astrophysics Data System (ADS)

Bordoloi, Manobjyoti; Saikia, Surovi; Bordoloi, Prasanta K.; Kolita, Bhaskor; Dutta, Partha P.; Bhuyan, Purnajyoti D.; Dutta, Subhas C.; Rao, Paruchuri G.

2017-08-01

The aim of this study was to isolate and characterize bioactive secondary metabolites from the flora of the Indo-Burma biodiversity belt for controlling leaf blight disease of Solanum khasianum Clarke (Solanaceae) caused by Alternaria tenuissima and Alternaria alternata during commercial cultivation, the berries of which contains 1.80-3.45% solasodine, a major raw material for steroid drug industries. Three new and two white powdered compounds were extracted from Cinnamomum obtusifolium (Roxb.) Nees (Lauraceae), Elaeocarpus lanceifolius (Roxb.) (Elaeocarpaceae) and Baccaurea sapida (Roxb.) Mull. Arg. (Euphorbiaceae). New compounds were characterized as Triacontanoic acid (1), octatriacontan-1-ol (2) and dotriacontane (3) isolated from C. obtusfolium and E. lanceofolius by 1H, 13C NMR and mass spectroscopy respectively. Other two known compounds were palmitic acid (4) and oleic acid (5) and from B. sapida. Complete inhibition of pathogenic fungi A.tenuissima and A. alternata were observed for compound 2 and 3. Further, in-silico molecular binding analysis of these compounds towards endopolygalacturonase, β-isopropyl dehydrogenase, plasma membrane ATPase, calmodulin, ACR-toxin biosynthesis hydroxylase and synthatase peptide (transcription regulator of Amt-gene) of A. tenuissima and A.alternata revealed that they are effective in inhibiting multiple targets. The antifungal potential of three new isolated compounds from C. obtusifolium and E. lanceifolius is reported for the first time. The results indicate the possible use of triacontanoic acid, octatriacontan-1-ol and dotriacontane as potential antifungal agents.

Erwinia amylovora Novel Plasmid pEI70: Complete Sequence, Biogeography, and Role in Aggressiveness in the Fire Blight Phytopathogen

PubMed Central

Llop, Pablo; Cabrefiga, Jordi; Smits, Theo H. M.; Dreo, Tanja; Barbé, Silvia; Pulawska, Joanna; Bultreys, Alain; Blom, Jochen; Duffy, Brion; Montesinos, Emilio; López, María M.

2011-01-01

Comparative genomics of several strains of Erwinia amylovora, a plant pathogenic bacterium causal agent of fire blight disease, revealed that its diversity is primarily attributable to the flexible genome comprised of plasmids. We recently identified and sequenced in full a novel 65.8 kb plasmid, called pEI70. Annotation revealed a lack of known virulence-related genes, but found evidence for a unique integrative conjugative element related to that of other plant and human pathogens. Comparative analyses using BLASTN showed that pEI70 is almost entirely included in plasmid pEB102 from E. billingiae, an epiphytic Erwinia of pome fruits, with sequence identities superior to 98%. A duplex PCR assay was developed to survey the prevalence of plasmid pEI70 and also that of pEA29, which had previously been described in several E. amylovora strains. Plasmid pEI70 was found widely dispersed across Europe with frequencies of 5–92%, but it was absent in E. amylovora analyzed populations from outside of Europe. Restriction analysis and hybridization demonstrated that this plasmid was identical in at least 13 strains. Curing E. amylovora strains of pEI70 reduced their aggressiveness on pear, and introducing pEI70 into low-aggressiveness strains lacking this plasmid increased symptoms development in this host. Discovery of this novel plasmid offers new insights into the biogeography, evolution and virulence determinants in E. amylovora. PMID:22174857

Discovery of Plant Phenolic Compounds That Act as Type III Secretion System Inhibitors or Inducers of the Fire Blight Pathogen, Erwinia amylovora

PubMed Central

Khokhani, Devanshi; Zhang, Chengfang; Li, Yan; Wang, Qi; Zeng, Quan; Yamazaki, Akihiro; Hutchins, William; Zhou, Shan-Shan

2013-01-01

Erwinia amylovora causes a devastating disease called fire blight in rosaceous plants. The type III secretion system (T3SS) is one of the important virulence factors utilized by E. amylovora in order to successfully infect its hosts. By using a green fluorescent protein (GFP) reporter construct combined with a high-throughput flow cytometry assay, a library of phenolic compounds and their derivatives was studied for their ability to alter the expression of the T3SS. Based on the effectiveness of the compounds on the expression of the T3SS pilus, the T3SS inhibitors 4-methoxy-cinnamic acid (TMCA) and benzoic acid (BA) and one T3SS inducer, trans-2-(4-hydroxyphenyl)-ethenylsulfonate (EHPES), were chosen for further study. Both the T3SS inhibitors (TMCA and BA) and the T3SS inducer (EHPES) were found to alter the expression of T3SS through the HrpS-HrpL pathway. Additionally, TMCA altered T3SS expression through the rsmBEa-RsmAEa system. Finally, we found that TMCA and BA weakened the hypersensitive response (HR) in tobacco by suppressing the T3SS of E. amylovora. In our study, we identified phenolic compounds that specifically targeted the T3SS. The T3SS inhibitor may offer an alternative approach to antimicrobial therapy by targeting virulence factors of bacterial pathogens. PMID:23770912

Erwinia amylovora novel plasmid pEI70: complete sequence, biogeography, and role in aggressiveness in the fire blight phytopathogen.

PubMed

Llop, Pablo; Cabrefiga, Jordi; Smits, Theo H M; Dreo, Tanja; Barbé, Silvia; Pulawska, Joanna; Bultreys, Alain; Blom, Jochen; Duffy, Brion; Montesinos, Emilio; López, María M

2011-01-01

Comparative genomics of several strains of Erwinia amylovora, a plant pathogenic bacterium causal agent of fire blight disease, revealed that its diversity is primarily attributable to the flexible genome comprised of plasmids. We recently identified and sequenced in full a novel 65.8 kb plasmid, called pEI70. Annotation revealed a lack of known virulence-related genes, but found evidence for a unique integrative conjugative element related to that of other plant and human pathogens. Comparative analyses using BLASTN showed that pEI70 is almost entirely included in plasmid pEB102 from E. billingiae, an epiphytic Erwinia of pome fruits, with sequence identities superior to 98%. A duplex PCR assay was developed to survey the prevalence of plasmid pEI70 and also that of pEA29, which had previously been described in several E. amylovora strains. Plasmid pEI70 was found widely dispersed across Europe with frequencies of 5-92%, but it was absent in E. amylovora analyzed populations from outside of Europe. Restriction analysis and hybridization demonstrated that this plasmid was identical in at least 13 strains. Curing E. amylovora strains of pEI70 reduced their aggressiveness on pear, and introducing pEI70 into low-aggressiveness strains lacking this plasmid increased symptoms development in this host. Discovery of this novel plasmid offers new insights into the biogeography, evolution and virulence determinants in E. amylovora.

Discovery of plant phenolic compounds that act as type III secretion system inhibitors or inducers of the fire blight pathogen, Erwinia amylovora.

PubMed

Khokhani, Devanshi; Zhang, Chengfang; Li, Yan; Wang, Qi; Zeng, Quan; Yamazaki, Akihiro; Hutchins, William; Zhou, Shan-Shan; Chen, Xin; Yang, Ching-Hong

2013-09-01

Erwinia amylovora causes a devastating disease called fire blight in rosaceous plants. The type III secretion system (T3SS) is one of the important virulence factors utilized by E. amylovora in order to successfully infect its hosts. By using a green fluorescent protein (GFP) reporter construct combined with a high-throughput flow cytometry assay, a library of phenolic compounds and their derivatives was studied for their ability to alter the expression of the T3SS. Based on the effectiveness of the compounds on the expression of the T3SS pilus, the T3SS inhibitors 4-methoxy-cinnamic acid (TMCA) and benzoic acid (BA) and one T3SS inducer, trans-2-(4-hydroxyphenyl)-ethenylsulfonate (EHPES), were chosen for further study. Both the T3SS inhibitors (TMCA and BA) and the T3SS inducer (EHPES) were found to alter the expression of T3SS through the HrpS-HrpL pathway. Additionally, TMCA altered T3SS expression through the rsmBEa-RsmAEa system. Finally, we found that TMCA and BA weakened the hypersensitive response (HR) in tobacco by suppressing the T3SS of E. amylovora. In our study, we identified phenolic compounds that specifically targeted the T3SS. The T3SS inhibitor may offer an alternative approach to antimicrobial therapy by targeting virulence factors of bacterial pathogens.

Diffusible and Volatile Antifungal Compounds Produced by an Antagonistic Bacillus velezensis G341 against Various Phytopathogenic Fungi.

PubMed

Lim, Seong Mi; Yoon, Mi-Young; Choi, Gyung Ja; Choi, Yong Ho; Jang, Kyoung Soo; Shin, Teak Soo; Park, Hae Woong; Yu, Nan Hee; Kim, Young Ho; Kim, Jin-Cheol

2017-10-01

The aim of this study was to identify volatile and agar-diffusible antifungal metabolites produced by Bacillus sp. G341 with strong antifungal activity against various phytopathogenic fungi. Strain G341 isolated from four-year-old roots of Korean ginseng with rot symptoms was identified as Bacillus velezensis based on 16S rDNA and gyrA sequences. Strain G341 inhibited mycelial growth of all phytopathogenic fungi tested. In vivo experiment results revealed that n -butanol extract of fermentation broth effectively controlled the development of rice sheath blight, tomato gray mold, tomato late blight, wheat leaf rust, barley powdery mildew, and red pepper anthracnose. Two antifungal compounds were isolated from strain G341 and identified as bacillomycin L and fengycin A by MS/MS analysis. Moreover, volatile compounds emitted from strain G341 were found to be able to inhibit mycelial growth of various phytopathogenic fungi. Based on volatile compound profiles of strain G341 obtained through headspace collection and analysis on GC-MS, dimethylsulfoxide, 1-butanol, and 3-hydroxy-2-butanone (acetoin) were identified. Taken together, these results suggest that B. valezensis G341 can be used as a biocontrol agent for various plant diseases caused by phytopathogenic fungi.

Assessing Changes in Potato Canopy Caused by Late Blight in Organic Production Systems Through Uav-Based Pushbroom Imaging Spectrometer

NASA Astrophysics Data System (ADS)

Franceschini, M. H. D.; Bartholomeus, H.; van Apeldoorn, D.; Suomalainen, J.; Kooistra, L.

2017-08-01

Productivity of cropping systems can be constrained simultaneously by different limiting factors and approaches allowing to indicate and identify plants under stress in field conditions can be valuable for farmers and breeders. In organic production systems, sensing solutions are not frequently studied, despite their potential for crop traits retrieval and stress assessment. In this study, spectral data in the optical domain acquired using a pushbroom spectrometer on board of a unmanned aerial vehicle is used to evaluate the potential of this information for assessment of late blight (Phytophthora infestans) incidence on potato (Solanum tuberosum) under organic cultivation. Vegetation indices formulations with two and three spectral bands were tested for the complete range of the spectral information acquired (i.e., from 450 to 900 nm, with 10 nm of spectral resolution). This evaluation concerned the discrimination between plots cultivated with only one resistant potato variety in contrast with plots with a variety mixture, with resistant and susceptible cultivars. Results indicated that indices based on three spectral bands performed better and optimal wavelengths (i.e., near 490, 530 and 670 nm) are not only related to chlorophyll content but also to other leaf pigments like carotenoids.

Transcriptomic and Proteomic Analyses of Resistant Host Responses in Arachis diogoi Challenged with Late Leaf Spot Pathogen, Phaeoisariopsis personata

PubMed Central

Kumar, Dilip; Kirti, Pulugurtha Bharadwaja

2015-01-01

Late leaf spot is a serious disease of peanut caused by the imperfect fungus, Phaeoisariopsis personata. Wild diploid species, Arachis diogoi. is reported to be highly resistant to this disease and asymptomatic. The objective of this study is to investigate the molecular responses of the wild peanut challenged with the late leaf spot pathogen using cDNA-AFLP and 2D proteomic study. A total of 233 reliable, differentially expressed genes were identified in Arachis diogoi. About one third of the TDFs exhibit no significant similarity with the known sequences in the data bases. Expressed sequence tag data showed that the characterized genes are involved in conferring resistance in the wild peanut to the pathogen challenge. Several genes for proteins involved in cell wall strengthening, hypersensitive cell death and resistance related proteins have been identified. Genes identified for other proteins appear to function in metabolism, signal transduction and defence. Nineteen TDFs based on the homology analysis of genes associated with defence, signal transduction and metabolism were further validated by quantitative real time PCR (qRT-PCR) analyses in resistant wild species in comparison with a susceptible peanut genotype in time course experiments. The proteins corresponding to six TDFs were differentially expressed at protein level also. Differentially expressed TDFs and proteins in wild peanut indicate its defence mechanism upon pathogen challenge and provide initial breakthrough of genes possibly involved in recognition events and early signalling responses to combat the pathogen through subsequent development of resistivity. This is the first attempt to elucidate the molecular basis of the response of the resistant genotype to the late leaf spot pathogen, and its defence mechanism. PMID:25646800

Tissue-specific changes of glutamine synthetase activity in oats after rhizosphere infestation by Pseudomonas syringae pv. tabaci. Final report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Knight, T.J.; Temple, S.; Sengupta-Gopalan, C.

1996-05-15

Oats (Avena sativa L. lodi) tolerant of rhizosphere infestation by Pseudomonas syringae pv. tabaci when challenged by the pathogen experience tissue-specific alterations of ammonia assimilatory capabilities. Altered ammonia assimilatory potentials between root and leaf tissue result from selective inactivation of glutamine synthetase (GS) by the toxin Tabtoxinine-B-lactam (TBL). Root GS is sensitive and leaf GSs are resistant to TBL inactivation. With prolonged challenge by the pathogen root GS activity decreases but leaf GS specific activity increase. Higher leaf GS activity is due to decreased rates of degradation rather than increased GS synthesis. Higher leaf GS activity and elevated levels ofmore » GS polypeptide appear to result from a limited interaction between GS and TBL leading to the accumulation of a less active but more stable GS holoenzyme. Tolerant challenged oats besides surviving rhizosphere infestation, experience enhanced growth. A strong correlation exists between leaf GS activity and whole plant fresh weight, suggesting that tissue-specific changes in ammonia assimilatory capability provides the plant a more efficient mechanism for uptake and utilization of nitrogen.« less

The signal peptide-like segment of hpaXm is required for its association to the cell wall in transgenic tobacco plants

PubMed Central

Li, Le; Miao, Weiguo; Liu, Wenbo; Zhang, Shujian

2017-01-01

Harpins, encoded by hrp (hypersensitive response and pathogenicity) genes of Gram-negative plant pathogens, are elicitors of hypersensitive response (HR). HpaXm is a novel harpin-like protein described from cotton leaf blight bacteria, Xanthomonas citri subsp. malvacearum—a synonym of X. campestris pv. malvacearum (Smith 1901–1978). A putative signal peptide (1-MNSLNTQIGANSSFL-15) of hpaXm was predicted in the nitroxyl-terminal (N-terminal)by SignalP (SignalP 3.0 server). Here, we explored the function of the N-terminal leader peptide like segment of hpaXm using transgenic tobacco (Nicotiana tabacum cv. Xanthi nc.). Transgenic tobacco lines expressing the full-length hpaXm and the signal peptide-like segment-deleted mutant hpaXmΔLP were developed using transformation mediated by Agrobacterium tumefaciens. The target genes were confirmed integrated into the tobacco genomes and expressed normally. Using immune colloidal-gold detection technique, hpaXm protein was found to be transferred to the cytoplasm, the cell membrane, and organelles such as chloroplasts, mitochondria, and nucleus, as well as the cell wall. However, the deletion mutant hpaXmΔLP expressed in transgenic tobacco was found unable to cross the membrane to reach the cell wall. Additionally, soluble proteins extracted from plants transformed with hpaXm and hpaXmΔLP were bio-active. Defensive micro-HR induced by the transgene expression of hpaXm and hpaXmΔLP were observed on transgenic tobacco leaves. Disease resistance bioassays to tobacco mosaic virus (TMV) showed that tobacco plants transformed with hpaXm and with hpaXmΔLP exhibited enhanced resistance to TMV. In summary, the N-terminal signal peptide-like segment (1–45 bp) in hpaXm sequence is not necessary for transgene expression, bioactivity of hpaXm and resistance to TMV in transgenic tobacco, but is required for the protein to be translocated to the cell wall. PMID:28141855

Development of disease-resistant rice using regulatory components of induced disease resistance

PubMed Central

Takatsuji, Hiroshi

2014-01-01

Infectious diseases cause huge crop losses annually. In response to pathogen attacks, plants activate defense systems that are mediated through various signaling pathways. The salicylic acid (SA) signaling pathway is the most powerful of these pathways. Several regulatory components of the SA signaling pathway have been identified, and are potential targets for genetic manipulation of plants’ disease resistance. However, the resistance associated with these regulatory components is often accompanied by fitness costs; that is, negative effects on plant growth and crop yield. Chemical defense inducers, such as benzothiadiazole and probenazole, act on the SA pathway and induce strong resistance to various pathogens without major fitness costs, owing to their ‘priming effect.’ Studies on how benzothiadiazole induces disease resistance in rice have identified WRKY45, a key transcription factor in the branched SA pathway, and OsNPR1/NH1. Rice plants overexpressing WRKY45 were extremely resistant to rice blast disease caused by the fungus Magnaporthe oryzae and bacterial leaf blight disease caused by Xanthomonas oryzae pv. oryzae (Xoo), the two major rice diseases. Disease resistance is often accompanied by fitness costs; however, WRKY45 overexpression imposed relatively small fitness costs on rice because of its priming effect. This priming effect was similar to that of chemical defense inducers, although the fitness costs were amplified by some environmental factors. WRKY45 is degraded by the ubiquitin–proteasome system, and the dual role of this degradation partly explains the priming effect. The synergistic interaction between SA and cytokinin signaling that activates WRKY45 also likely contributes to the priming effect. With a main focus on these studies, I review the current knowledge of SA-pathway-dependent defense in rice by comparing it with that in Arabidopsis, and discuss potential strategies to develop disease-resistant rice using signaling components. PMID:25431577

[Field resistance of Phytophthora melonis to metalaxyl in South China].

PubMed

Wu, Yongguan; Lu, Shaofeng; Huang, Siliang; Fu, Gang; Chen, Liang; Xie, Dasen; Li, Qiqin; Cen, Zhenlu

2011-08-01

Phytophthora melonis is the casual agent of wax gourd and cucumber Phytophthora blight which becomes a constraint for sustainable production of the related crops. Metalaxyl is one of the principal fungicides for controlling the disease now. The objectives of the present study were: (1) to investigate the baseline sensitivity and field resistance of P. melonis to metalaxyl in South China; (2) to test the occurrence of metalaxyl-resistant mutants from metalaxyl-sensitive wild type strains exposed to the fungicide; and (3) to monitor the development of metalaxyl resistance in P. melonis population. Over 400 samples of wax gourd and cucumber Phytophthora blight were collected from Guangxi Zhuang Autonomous Region and Guangdong province during 2007-2010, and 193 strains of P. melonis were isolated and purified. The sensitivity of the isolated strains to metalaxyl was tested using mycelial growth rate method in vitro and floating-leaf-disk method in vivo, respectively. The metalaxyl-sensitive strains were induced on PDA plates containing 10 microg/mL metalaxyl. The sensitive, moderately resistant and resistant strains were recorded as 29.0% , 18.1% and 52.8%, respectively, among 193 tested strains. The frequency and level of resistance of P. melonis from Guangdong were higher than that from Guangxi. The strains from cucumber was generally more resistant to metalaxyl than those from wax gourd. The metalaxyl-resistant strains were frequently detected as predominant populations in most of the sampling sites and the highest resistance index (4226.9) was confirmed. Metalaxyl-resistant (M1r) mutants could be isolated from approximately 60% of the sensitive wild-type strains. The resistance level of the M mutants was 189-407 times higher than that of their sensitive parental strains. The EC50 values of 9 sensitive strains from a sampling site without a record of phenylamide fungicide application ranged from 0.0429 to 0.5461 microg/mL. Their mean EC50 value (0.3200 +/- 0.1617 microg/mL) was considered as the baseline sensitivity of P. melonis to metalaxyl in South China. Metalaxyl-resistant strains universally occur in South China, especially in the vegetable-growing areas with a longer history of metalaxyl application. The establishment of the baseline sensitivity of P. melonis to metalaxyl will provide a science-based guide for evaluating and further monitoring resistance of the pathogen to the fungicide.

Analyses of genetic diversity of bacterial blight pathogen, Xanthomonas oryzae pv. oryzae using IS1112 in Bangladesh.

PubMed

Islam, Md Rashidul; Alam, Md Samiul; Khan, Ashik Iqbal; Hossain, Ismail; Adam, Lorne R; Daayf, Fouad

2016-01-01

Bacterial blight (BB) is caused by Xanthomonas oryzae pv. oryzae (Xoo), a most destructive disease of rice, mostly in Asia, including Bangladesh. Altogether 96 isolates of Xoo were collected from 19 rice-growing districts of Bangladesh in both the rain-fed and irrigated seasons of 2014 to assess their pathotypic and genetic variation. Pathotypic analyses were carried out on a set of 12 Near Isogenic Lines (NILs) of rice containing a single resistance gene and two check varieties IR24 and TN1 by the leaf clipping inoculation method. A total of 24 pathotypes were identified based on their virulence patterns on the NILs tested. Among these, pathotypes VII, XII and XIV, considered as major, containing a maximum number of isolates (9.38% each), are frequently distributed in seven northern to mid-eastern districts of Bangladesh. The most virulent pathotype I was recorded in the Habiganj and Brahmanbaria districts. The molecular analysis of variability among the isolates was carried out through PCR analysis using multi-locus primers Jel1 and Jel2 (based on the repetitive element IS1112 in the Xoo genome). Using the genotypic data, a dendrogram was constructed with 17 clusters along with 17 molecular haplotypes at the 65% similarity index. Cluster I was composed of 46 isolates considered as major, whereas clusters X, XI, XII and XVII were represented by a single isolate. A phenogram was constructed based on virulence to interpret the relationship between the pathotypes and the molecular haplotypes. At the 50% similarity level, among 10 clusters, cluster I, considered as major, consisted of a maximum of 10 pathotypes out of 24. In case of haplotypes, a maximum of 7 haplotypes were obtained from pathotype XII, whereas pathotypes IX, X, XV, XXII and XXIV were represented by a single haplotype. However, the present study revealed that different isolates belonging to the same pathotypes belonged to different haplotypes. Conversely, genetically similar haplotypes were also detected from different pathotypes collected from separate districts. This relationship appeared due to a high degree of DNA polymorphism among strains within many pathotypes existing in Bangladesh. Copyright © 2016 Académie des sciences. Published by Elsevier SAS. All rights reserved.

Transcriptome profiling of soybean (Glycine max) roots challenged with pathogenic and non-pathogenic isolates of Fusarium oxysporum.

PubMed

Lanubile, Alessandra; Muppirala, Usha K; Severin, Andrew J; Marocco, Adriano; Munkvold, Gary P

2015-12-21

Fusarium oxysporum is one of the most common fungal pathogens causing soybean root rot and seedling blight in U.S.A. In a recent study, significant variation in aggressiveness was observed among isolates of F. oxysporum collected from roots in Iowa, ranging from highly pathogenic to weakly or non-pathogenic isolates. We used RNA-seq analysis to investigate the molecular aspects of the interactions of a partially resistant soybean genotype with non-pathogenic/pathogenic isolates of F. oxysporum at 72 and 96 h post inoculation (hpi). Markedly different gene expression profiles were observed in response to the two isolates. A peak of highly differentially expressed genes (HDEGs) was triggered at 72 hpi in soybean roots and the number of HDEGs was about eight times higher in response to the pathogenic isolate compared to the non-pathogenic one (1,659 vs. 203 HDEGs, respectively). Furthermore, the magnitude of induction was much greater in response to the pathogenic isolate. This response included a stronger activation of defense-related genes, transcription factors, and genes involved in ethylene biosynthesis, secondary and sugar metabolism. The obtained data provide an important insight into the transcriptional responses of soybean-F. oxysporum interactions and illustrate the more drastic changes in the host transcriptome in response to the pathogenic isolate. These results may be useful in the developing new methods of broadening resistance of soybean to F. oxysporum, including the over-expression of key soybean genes.

Soil moisture mediated interaction between Polygonatum biflorum and leaf spot disease

Treesearch

Robert J. II Warren; Erin Mordecai

2010-01-01

Fungal pathogens can regulate the abundance and distribution of natural plant populations by inhibiting the growth, survival, and reproduction of their hosts. The abiotic environment is a crucial component in host–pathogen interactions in natural plant populations as favorable conditions drive pathogen development, reproduction, and persistence. Foliar plant pathogens...

24 CFR 570.483 - Criteria for national objectives.

Code of Federal Regulations, 2013 CFR

2013-04-01

... prevention or elimination of slums or blight. Activities meeting one or more of the following criteria, in... elimination of slums or blight: (1) Activities to address slums or blight on an area basis. An activity will be considered to address prevention or elimination of slums or blight in an area if the state can...

24 CFR 570.483 - Criteria for national objectives.

Code of Federal Regulations, 2011 CFR

2011-04-01

... prevention or elimination of slums or blight. Activities meeting one or more of the following criteria, in... elimination of slums or blight: (1) Activities to address slums or blight on an area basis. An activity will be considered to address prevention or elimination of slums or blight in an area if the state can...

24 CFR 570.483 - Criteria for national objectives.

Code of Federal Regulations, 2012 CFR

2012-04-01

... prevention or elimination of slums or blight. Activities meeting one or more of the following criteria, in... elimination of slums or blight: (1) Activities to address slums or blight on an area basis. An activity will be considered to address prevention or elimination of slums or blight in an area if the state can...

24 CFR 570.483 - Criteria for national objectives.

Code of Federal Regulations, 2014 CFR

2014-04-01

... prevention or elimination of slums or blight. Activities meeting one or more of the following criteria, in... elimination of slums or blight: (1) Activities to address slums or blight on an area basis. An activity will be considered to address prevention or elimination of slums or blight in an area if the state can...

Selection of bean lines that combine resistance to web blight and common bacterial blight

USDA-ARS?s Scientific Manuscript database

Web blight caused by Thanatephorus cucumeris Frank (Donk) causes significant reductions in the yield and quality of beans produced in the humid, lowland tropics. A total of 644 lines from different breeding programs were evaluated for reaction to web blight and other diseases using conventional plan...

Effects of deoxynivalenol on content of chloroplast pigments in barley leaf tissues.

PubMed

Bushnell, W R; Perkins-Veazie, P; Russo, V M; Collins, J; Seeland, T M

2010-01-01

To understand further the role of deoxynivalenol (DON) in development of Fusarium head blight (FHB), we investigated effects of the toxin on uninfected barley tissues. Leaf segments, 1 to 1.2 cm long, partially stripped of epidermis were floated with exposed mesophyll in contact with DON solutions. In initial experiments with the leaf segments incubated in light, DON at 30 to 90 ppm turned portions of stripped tissues white after 48 to 96 h. The bleaching effect was greatly enhanced by addition of 1 to 10 mM Ca(2+), so that DON at 10 to 30 ppm turned virtually all stripped tissues white within 48 h. Content of chlorophylls a and b and of total carotenoid pigment was reduced. Loss of electrolytes and uptake of Evans blue indicated that DON had a toxic effect, damaging plasmalemmas in treated tissues before chloroplasts began to lose pigment. When incubated in the dark, leaf segments also lost electrolytes, indicating DON was toxic although the tissues remained green. Thus, loss of chlorophyll in light was due to photobleaching and was a secondary effect of DON, not required for toxicity. In contrast to bleaching effects, some DON treatments that were not toxic kept tissues green without bleaching or other signs of injury, indicating senescence was delayed compared with slow yellowing of untreated leaf segments. Cycloheximide, which like DON, inhibits protein synthesis, also bleached some tissues and delayed senescence of others. Thus, the effects of DON probably relate to its ability to inhibit protein synthesis. With respect to FHB, the results suggest DON may have multiple roles in host cells of infected head tissues, including delayed senescence in early stages of infection and contributing to bleaching and death of cells in later stages.

Antimicrobial fish gelatin films with olive leaf extract for inactivation of Listeria monocytogenes on ready-to-eat smoked salmon (abstract)

USDA-ARS?s Scientific Manuscript database

Olive leaf is a sizable by-product from the olive industry. Its use as antimicrobial/antioxidant ingredient in edible films for fish preservation was evaluated. Olive leaf powder (OLP) and its water/ethanol extract (OLPE) were tested against three foodborne pathogens: Listeria monocytogenes, Escheri...

Antimicrobial activities of Streptomyces pulcher, S. canescens and S. citreofluorescens against fungal and bacterial pathogens of tomato in vitro.

PubMed

el-Abyad, M S; el-Sayed, M A; el-Shanshoury, A R; el-Sabbagh, S M

1996-01-01

Thirty-seven actinomycete species isolated from fertile cultivated soils in Egypt were screened for the production of antimicrobial compounds against a variety of test organisms. Most of the isolates exhibited antimicrobial activities against Gram-positive, Gram-negative, and acid-fast bacteria, yeasts and filamentous fungi, with special attention to fungal and bacterial pathogens of tomato. On starch-nitrate agar, 14 strains were active against Fusarium oxysporum f.sp. lycopersici (the cause of Fusarium wilt), 18 against Verticillium albo-atrum (the cause of Verticillium wilt), and 18 against Alternaria solani (the cause of early blight). In liquid media, 14 isolates antagonized Pseudomonas solanacearum (the cause of bacterial wilt) and 20 antagonized Clavibacter michiganensis ssp. michiganensis (the cause of bacterial canker). The most active antagonists of the pathogenic microorganisms studied were found to be Streptomyces pulcher, S. canescens (syn. S. albidoflavus) and S. citreofluorescens (syn. S. anulatus). The antagonistic activities of S. pulcher and S. canescens against pathogenic fungi were assessed on solid media, and those of S. pulcher and S. citreofluorescens against pathogenic bacteria in liquid media under shaking conditions. The optimum culture conditions were determined.

Identification, Characterization and Full-Length Sequence Analysis of a Novel Polerovirus Associated with Wheat Leaf Yellowing Disease

PubMed Central

Zhang, Peipei; Liu, Yan; Liu, Wenwen; Cao, Mengji; Massart, Sebastien; Wang, Xifeng

2017-01-01

To identify the pathogens responsible for leaf yellowing symptoms on wheat samples collected from Jinan, China, we tested for the presence of three known barley/wheat yellow dwarf viruses (BYDV-GAV, -PAV, WYDV-GPV) (most likely pathogens) using RT-PCR. A sample that tested negative for the three viruses was selected for small RNA sequencing. Twenty-five million sequences were generated, among which 5% were of viral origin. A novel polerovirus was discovered and temporarily named wheat leaf yellowing-associated virus (WLYaV). The full genome of WLYaV corresponds to 5,772 nucleotides (nt), with six AUG-initiated open reading frames, one non-AUG-initiated open reading frame, and three untranslated regions, showing typical features of the family Luteoviridae. Sequence comparison and phylogenetic analyses suggested that WLYaV had the closest relationship with sugarcane yellow leaf virus (ScYLV), but the identities of full genomic nucleotides and deduced amino acid sequence of coat protein (CP) were 64.9 and 86.2%, respectively, below the species demarcation thresholds (90%) in the family Luteoviridae. Furthermore, agroinoculation of Nicotiana benthamiana leaves with a cDNA clone of WLYaV caused yellowing symptoms on the plant. Our study adds a new polerovirus that is associated with wheat leaf yellowing disease, which would help to identify and control pathogens of wheat. PMID:28932215

Identification, Characterization and Full-Length Sequence Analysis of a Novel Polerovirus Associated with Wheat Leaf Yellowing Disease.

PubMed

Zhang, Peipei; Liu, Yan; Liu, Wenwen; Cao, Mengji; Massart, Sebastien; Wang, Xifeng

2017-01-01

To identify the pathogens responsible for leaf yellowing symptoms on wheat samples collected from Jinan, China, we tested for the presence of three known barley/wheat yellow dwarf viruses (BYDV-GAV, -PAV, WYDV-GPV) (most likely pathogens) using RT-PCR. A sample that tested negative for the three viruses was selected for small RNA sequencing. Twenty-five million sequences were generated, among which 5% were of viral origin. A novel polerovirus was discovered and temporarily named wheat leaf yellowing-associated virus (WLYaV). The full genome of WLYaV corresponds to 5,772 nucleotides (nt), with six AUG-initiated open reading frames, one non-AUG-initiated open reading frame, and three untranslated regions, showing typical features of the family Luteoviridae . Sequence comparison and phylogenetic analyses suggested that WLYaV had the closest relationship with sugarcane yellow leaf virus (ScYLV), but the identities of full genomic nucleotides and deduced amino acid sequence of coat protein (CP) were 64.9 and 86.2%, respectively, below the species demarcation thresholds (90%) in the family Luteoviridae . Furthermore, agroinoculation of Nicotiana benthamiana leaves with a cDNA clone of WLYaV caused yellowing symptoms on the plant. Our study adds a new polerovirus that is associated with wheat leaf yellowing disease, which would help to identify and control pathogens of wheat.

Uncovering leaf rust responsive miRNAs in wheat (Triticum aestivum L.) using high-throughput sequencing and prediction of their targets through degradome analysis.

PubMed

Kumar, Dhananjay; Dutta, Summi; Singh, Dharmendra; Prabhu, Kumble Vinod; Kumar, Manish; Mukhopadhyay, Kunal

2017-01-01

Deep sequencing identified 497 conserved and 559 novel miRNAs in wheat, while degradome analysis revealed 701 targets genes. QRT-PCR demonstrated differential expression of miRNAs during stages of leaf rust progression. Bread wheat (Triticum aestivum L.) is an important cereal food crop feeding 30 % of the world population. Major threat to wheat production is the rust epidemics. This study was targeted towards identification and functional characterizations of micro(mi)RNAs and their target genes in wheat in response to leaf rust ingression. High-throughput sequencing was used for transcriptome-wide identification of miRNAs and their expression profiling in retort to leaf rust using mock and pathogen-inoculated resistant and susceptible near-isogenic wheat plants. A total of 1056 mature miRNAs were identified, of which 497 miRNAs were conserved and 559 miRNAs were novel. The pathogen-inoculated resistant plants manifested more miRNAs compared with the pathogen infected susceptible plants. The miRNA counts increased in susceptible isoline due to leaf rust, conversely, the counts decreased in the resistant isoline in response to pathogenesis illustrating precise spatial tuning of miRNAs during compatible and incompatible interaction. Stem-loop quantitative real-time PCR was used to profile 10 highly differentially expressed miRNAs obtained from high-throughput sequencing data. The spatio-temporal profiling validated the differential expression of miRNAs between the isolines as well as in retort to pathogen infection. Degradome analysis provided 701 predicted target genes associated with defense response, signal transduction, development, metabolism, and transcriptional regulation. The obtained results indicate that wheat isolines employ diverse arrays of miRNAs that modulate their target genes during compatible and incompatible interaction. Our findings contribute to increase knowledge on roles of microRNA in wheat-leaf rust interactions and could help in rust resistance breeding programs.

Comparative transcriptome analysis of a lowly virulent strain of Erwinia amylovora in shoots of two apple cultivars - susceptible and resistant to fire blight.

PubMed

Puławska, Joanna; Kałużna, Monika; Warabieda, Wojciech; Mikiciński, Artur

2017-11-13

Erwinia amylovora is generally considered to be a homogeneous species in terms of phenotypic and genetic features. However, strains show variation in their virulence, particularly on hosts with different susceptibility to fire blight. We applied the RNA-seq technique to elucidate transcriptome-level changes of the lowly virulent E. amylovora 650 strain during infection of shoots of susceptible (Idared) and resistant (Free Redstar) apple cultivars. The highest number of differentially expressed E. amylovora genes between the two apple genotypes was observed at 24 h after inoculation. Six days after inoculation, only a few bacterial genes were differentially expressed in the susceptible and resistant apple cultivars. The analysis of differentially expressed gene functions showed that generally, higher expression of genes related to stress response and defence against toxic compounds was observed in Free Redstar. Also in this cultivar, higher expression of flagellar genes (FlaI), which are recognized as PAMP (pathogen-associated molecular pattern) by the innate immune systems of plants, was noted. Additionally, several genes that have not yet been proven to play a role in the pathogenic abilities of E. amylovora were found to be differentially expressed in the two apple cultivars. This RNA-seq analysis generated a novel dataset describing the transcriptional response of the lowly virulent strain of E. amylovora in susceptible and resistant apple cultivar. Most genes were regulated in the same way in both apple cultivars, but there were also some cultivar-specific responses suggesting that the environment in Free Redstar is more stressful for bacteria what can be the reason of their inability to infect of this cultivar. Among genes with the highest fold change in expression between experimental combinations or with the highest transcript abundance, there are many genes without ascribed functions, which have never been tested for their role in pathogenicity. Overall, this study provides the first transcriptional profile by RNA-seq of E. amylovora during infection of a host plant and insights into the transcriptional response of this pathogen in the environments of susceptible and resistant apple plants.

Effects of One Cycle of Recurrent Selection for Early Blight Resistance in a Diploid Hybrid Solanum phureja-S. stenotomum Population

USDA-ARS?s Scientific Manuscript database

Early blight, caused by Alternaria solani, is the second most important foliar disease in potatoes, after late blight, around the world. Heritable early blight resistance was previously identified in a diploid hybrid population of Solanum phureja-S. stenotomum (phu-stn). Seventy-two clones, consis...

Whole-leaf wash improves chlorine efficacy for microbial reduction and prevents pathogen cross-contamination during fresh-cut lettuce processing.

PubMed

Nou, Xiangwu; Luo, Yaguang

2010-06-01

Currently, most fresh-cut processing facilities in the United States use chlorinated water or other sanitizer solutions for microbial reduction after lettuce is cut. Freshly cut lettuce releases significant amounts of organic matter that negatively impacts the effectiveness of chlorine or other sanitizers for microbial reduction. The objective of this study is to evaluate whether a sanitizer wash before cutting improves microbial reduction efficacy compared to a traditional postcutting sanitizer wash. Romaine lettuce leaves were quantitatively inoculated with E. coli O157:H7 strains and washed in chlorinated water before or after cutting, and E. coli O157:H7 cells that survived the washing process were enumerated to determine the effectiveness of microbial reduction for the 2 cutting and washing sequences. Whole-leaf washing in chlorinated water improved pathogen reduction by approximately 1 log unit over traditional cut-leaf sanitization. Similar improvement in the reduction of background microflora was also observed. Inoculated "Lollo Rossa" red lettuce leaves were mixed with noninoculated Green-Leaf lettuce leaves to evaluate pathogen cross-contamination during processing. High level (96.7% subsamples, average MPN 0.6 log CFU/g) of cross-contamination of noninoculated green leaves by inoculated red leaves was observed when mixed lettuce leaves were cut prior to washing in chlorinated water. In contrast, cross-contamination of noninoculated green leaves was significantly reduced (3.3% of subsamples, average MPN

The CC-NB-LRR-Type Rdg2a Resistance Gene Confers Immunity to the Seed-Borne Barley Leaf Stripe Pathogen in the Absence of Hypersensitive Cell Death

PubMed Central

Collins, Nicholas C.; Consonni, Gabriella; Stanca, Antonio M.; Schulze-Lefert, Paul; Valè, Giampiero

2010-01-01

Background Leaf stripe disease on barley (Hordeum vulgare) is caused by the seed-transmitted hemi-biotrophic fungus Pyrenophora graminea. Race-specific resistance to leaf stripe is controlled by two known Rdg (Resistance to Drechslera graminea) genes: the H. spontaneum-derived Rdg1a and Rdg2a, identified in H. vulgare. The aim of the present work was to isolate the Rdg2a leaf stripe resistance gene, to characterize the Rdg2a locus organization and evolution and to elucidate the histological bases of Rdg2a-based leaf stripe resistance. Principal Findings We describe here the positional cloning and functional characterization of the leaf stripe resistance gene Rdg2a. At the Rdg2a locus, three sequence-related coiled-coil, nucleotide-binding site, and leucine-rich repeat (CC-NB-LRR) encoding genes were identified. Sequence comparisons suggested that paralogs of this resistance locus evolved through recent gene duplication, and were subjected to frequent sequence exchange. Transformation of the leaf stripe susceptible cv. Golden Promise with two Rdg2a-candidates under the control of their native 5′ regulatory sequences identified a member of the CC-NB-LRR gene family that conferred resistance against the Dg2 leaf stripe isolate, against which the Rdg2a-gene is effective. Histological analysis demonstrated that Rdg2a-mediated leaf stripe resistance involves autofluorescing cells and prevents pathogen colonization in the embryos without any detectable hypersensitive cell death response, supporting a cell wall reinforcement-based resistance mechanism. Conclusions This work reports about the cloning of a resistance gene effective against a seed borne disease. We observed that Rdg2a was subjected to diversifying selection which is consistent with a model in which the R gene co-evolves with a pathogen effector(s) gene. We propose that inducible responses giving rise to physical and chemical barriers to infection in the cell walls and intercellular spaces of the barley embryo tissues represent mechanisms by which the CC-NB-LRR-encoding Rdg2a gene mediates resistance to leaf stripe in the absence of hypersensitive cell death. PMID:20844752

Comparative Genomics of Erwinia amylovora and Related Erwinia Species—What do We Learn?

PubMed Central

Zhao, Youfu; Qi, Mingsheng

2011-01-01

Erwinia amylovora, the causal agent of fire blight disease of apples and pears, is one of the most important plant bacterial pathogens with worldwide economic significance. Recent reports on the complete or draft genome sequences of four species in the genus Erwinia, including E. amylovora, E. pyrifoliae, E. tasmaniensis, and E. billingiae, have provided us near complete genetic information about this pathogen and its closely-related species. This review describes in silico subtractive hybridization-based comparative genomic analyses of eight genomes currently available, and highlights what we have learned from these comparative analyses, as well as genetic and functional genomic studies. Sequence analyses reinforce the assumption that E. amylovora is a relatively homogeneous species and support the current classification scheme of E. amylovora and its related species. The potential evolutionary origin of these Erwinia species is also proposed. The current understanding of the pathogen, its virulence mechanism and host specificity from genome sequencing data is summarized. Future research directions are also suggested. PMID:24710213

Reconstructing genome evolution in historic samples of the Irish potato famine pathogen

PubMed Central

Martin, Michael D.; Cappellini, Enrico; Samaniego, Jose A.; Zepeda, M. Lisandra; Campos, Paula F.; Seguin-Orlando, Andaine; Wales, Nathan; Orlando, Ludovic; Ho, Simon Y. W.; Dietrich, Fred S.; Mieczkowski, Piotr A.; Heitman, Joseph; Willerslev, Eske; Krogh, Anders; Ristaino, Jean B.; Gilbert, M. Thomas P.

2013-01-01

Responsible for the Irish potato famine of 1845–49, the oomycete pathogen Phytophthora infestans caused persistent, devastating outbreaks of potato late blight across Europe in the 19th century. Despite continued interest in the history and spread of the pathogen, the genome of the famine-era strain remains entirely unknown. Here we characterize temporal genomic changes in introduced P. infestans. We shotgun sequence five 19th-century European strains from archival herbarium samples—including the oldest known European specimen, collected in 1845 from the first reported source of introduction. We then compare their genomes to those of extant isolates. We report multiple distinct genotypes in historical Europe and a suite of infection-related genes different from modern strains. At virulence-related loci, several now-ubiquitous genotypes were absent from the historical gene pool. At least one of these genotypes encodes a virulent phenotype in modern strains, which helps explain the 20th century’s episodic replacements of European P. infestans lineages. PMID:23863894

Use of remote sensing for land use policy formulation

NASA Technical Reports Server (NTRS)

1981-01-01

Progress in studies for using remotely sensed data for assessing crop stress and in crop estimation is reported. The estimation of acreage of small forested areas in the southern lower peninsula of Michigan using LANDSAT data is evaluated. Damage to small grains caused by the cereal leaf beetle was assessed through remote sensing. The remote detection of X-disease of peach and cherry trees and of fire blight of pear and apple trees was investigated. The reliability of improving on standard methods of crop production estimation was demonstrated. Areas of virus infestation in vineyards and blueberry fields in western and southwestern Michigan were identified. The installation and systems integration of a microcomputer system for processing and making available remotely sensed data are described.

Antifungal activities of Bacillus thuringiensis isolates on barley and cucumber powdery mildews.

PubMed

Choi, Gyung Ja; Kim, Jin-Cheol; Jang, Kyoung Soo; Lee, Dong-Hyun

2007-12-01

Fourteen Bacillus thuringiensis isolates having both insecticidal activity and in vitro antifungal activity were selected and tested for in vivo antifungal activity against tomato late blight, wheat leaf rust, tomato gray mold, and barley powdery mildew in growth chambers. All the isolates represented more than 70% disease control efficacy against at least one of four plant diseases. Specifically, 12 isolates exhibited strong control activity against barley powdery mildew. Under glasshouse conditions, four (50-02, 52-08, 52-16, and 52- 18) of the isolates also displayed potent control efficacy against cucumber powdery mildew. To our knowledge, this is the first report of B. thuringiensis isolates that have disease control efficacy against powdery mildew of barley and cucumber as well as insecticidal activity.

Engineered disease resistance in cotton using RNA-interference to knock down cotton leaf curl kokhran virus-Burewala and cotton leaf curl Multan betasatellite

USDA-ARS?s Scientific Manuscript database

Cotton Leaf Curl virus Disease (CLCuD) has caused enormous losses in cotton (Gossypium hirsutum) production in Pakistan. RNA interference (RNAi) is an emerging technique that could knock out CLCuD by targeting different regions of the pathogen genome that are important for replication, transcription...

Hyperspectral recognition of processing tomato early blight based on GA and SVM

NASA Astrophysics Data System (ADS)

Yin, Xiaojun; Zhao, SiFeng

2013-03-01

Processing tomato early blight seriously affect the yield and quality of its.Determine the leaves spectrum of different disease severity level of processing tomato early blight.We take the sensitive bands of processing tomato early blight as support vector machine input vector.Through the genetic algorithm(GA) to optimize the parameters of SVM, We could recognize different disease severity level of processing tomato early blight.The result show:the sensitive bands of different disease severity levels of processing tomato early blight is 628-643nm and 689-692nm.The sensitive bands are as the GA and SVM input vector.We get the best penalty parameters is 0.129 and kernel function parameters is 3.479.We make classification training and testing by polynomial nuclear,radial basis function nuclear,Sigmoid nuclear.The best classification model is the radial basis function nuclear of SVM. Training accuracy is 84.615%,Testing accuracy is 80.681%.It is combined GA and SVM to achieve multi-classification of processing tomato early blight.It is provided the technical support of prediction processing tomato early blight occurrence, development and diffusion rule in large areas.

Erwinia amylovora Expresses Fast and Simultaneously hrp/dsp Virulence Genes during Flower Infection on Apple Trees

PubMed Central

Pester, Doris; Milčevičová, Renáta; Schaffer, Johann; Wilhelm, Eva; Blümel, Sylvia

2012-01-01

Background Pathogen entry through host blossoms is the predominant infection pathway of the Gram-negative bacterium Erwinia amylovora leading to manifestation of the disease fire blight. Like in other economically important plant pathogens, E. amylovora pathogenicity depends on a type III secretion system encoded by hrp genes. However, timing and transcriptional order of hrp gene expression during flower infections are unknown. Methodology/Principal Findings Using quantitative real-time PCR analyses, we addressed the questions of how fast, strong and uniform key hrp virulence genes and the effector dspA/E are expressed when bacteria enter flowers provided with the full defense mechanism of the apple plant. In non-invasive bacterial inoculations of apple flowers still attached to the tree, E. amylovora activated expression of key type III secretion genes in a narrow time window, mounting in a single expression peak of all investigated hrp/dspA/E genes around 24–48 h post inoculation (hpi). This single expression peak coincided with a single depression in the plant PR-1 expression at 24 hpi indicating transient manipulation of the salicylic acid pathway as one target of E. amylovora type III effectors. Expression of hrp/dspA/E genes was highly correlated to expression of the regulator hrpL and relative transcript abundances followed the ratio: hrpA>hrpN>hrpL>dspA/E. Acidic conditions (pH 4) in flower infections led to reduced virulence/effector gene expression without the typical expression peak observed under natural conditions (pH 7). Conclusion/Significance The simultaneous expression of hrpL, hrpA, hrpN, and the effector dspA/E during early floral infection indicates that speed and immediate effector transmission is important for successful plant invasion. When this delicate balance is disturbed, e.g., by acidic pH during infection, virulence gene expression is reduced, thus partly explaining the efficacy of acidification in fire blight control on a molecular level. PMID:22412891

Characterization of Triticum aestivum Abscisic Acid Receptors and a Possible Role for These in Mediating Fusairum Head Blight Susceptibility in Wheat

PubMed Central

Gordon, Cameron S.; Rajagopalan, Nandhakishore; Risseeuw, Eddy P.; Surpin, Marci; Ball, Fraser J.; Barber, Carla J.; Buhrow, Leann M.; Clark, Shawn M.; Page, Jonathan E.; Todd, Chris D.; Abrams, Suzanne R.; Loewen, Michele C.

2016-01-01

Abscisic acid (ABA) is a well-characterized plant hormone, known to mediate developmental aspects as well as both abiotic and biotic stress responses. Notably, the exogenous application of ABA has recently been shown to increase susceptibility to the fungal pathogen Fusarium graminearum, the causative agent of Fusarium head blight (FHB) in wheat and other cereals. However roles and mechanisms associated with ABA’s modulation of pathogen responses remain enigmatic. Here the identification of putative ABA receptors from available genomic databases for Triticum aestivum (bread wheat) and Brachypodium distachyon (a model cereal) are reported. A number of these were cloned for recombinant expression and their functionality as ABA receptors confirmed by in vitro assays against protein phosphatases Type 2Cs. Ligand selectivity profiling of one of the wheat receptors (Ta_PYL2DS_FL) highlighted unique activities compared to Arabidopsis AtPYL5. Mutagenic analysis showed Ta_PYL2DS_FL amino acid D180 as being a critical contributor to this selectivity. Subsequently, a virus induced gene silencing (VIGS) approach was used to knockdown wheat Ta_PYL4AS_A (and similar) in planta, yielding plants with increased early stage resistance to FHB progression and decreased mycotoxin accumulation. Together these results confirm the existence of a family of ABA receptors in wheat and Brachypodium and present insight into factors modulating receptor function at the molecular level. That knockdown of Ta_PYL4AS_A (and similar) leads to early stage FHB resistance highlights novel targets for investigation in the future development of disease resistant crops. PMID:27755583

Small-molecule inhibitors suppress the expression of both type III secretion and amylovoran biosynthesis genes in Erwinia amylovora.

PubMed

Yang, Fan; Korban, Schuyler S; Pusey, P Lawrence; Elofsson, Michael; Sundin, George W; Zhao, Youfu

2014-01-01

The type III secretion system (T3SS) and exopolysaccharide (EPS) amylovoran are two essential pathogenicity factors in Erwinia amylovora, the causal agent of the serious bacterial disease fire blight. In this study, small molecules that inhibit T3SS gene expression in E. amylovora under hrp (hypersensitive response and pathogenicity)-inducing conditions were identified and characterized using green fluorescent protein (GFP) as a reporter. These compounds belong to salicylidene acylhydrazides and also inhibit amylovoran production. Microarray analysis of E. amylovora treated with compounds 3 and 9 identified a total of 588 significantly differentially expressed genes. Among them, 95 and 78 genes were activated and suppressed by both compounds, respectively, when compared with the dimethylsulphoxide (DMSO) control. The expression of the majority of T3SS genes in E. amylovora, including hrpL and the avrRpt2 effector gene, was suppressed by both compounds. Compound 3 also suppressed the expression of amylovoran precursor and biosynthesis genes. However, both compounds induced significantly the expression of glycogen biosynthesis genes and siderophore biosynthesis, regulatory and transport genes. Furthermore, many membrane, lipoprotein and exported protein-encoding genes were also activated by both compounds. Similar expression patterns were observed for compounds 1, 2 and 4. Using crab apple flower as a model, compound 3 was capable of reducing disease development in pistils. These results suggest a common inhibition mechanism shared by salicylidene acylhydrazides and indicate that small-molecule inhibitors that disable T3SS function could be explored to control fire blight disease. © 2013 BSPP AND JOHN WILEY & SONS LTD.

Interactions between Head Blight Pathogens: Consequences for Disease Development and Toxin Production in Wheat Spikes

PubMed Central

Siou, Dorothée; Gélisse, Sandrine; Laval, Valérie; Elbelt, Sonia; Repinçay, Cédric; Bourdat-Deschamps, Marjolaine; Lannou, Christian

2014-01-01

Head blight (HB) is one of the most damaging diseases on wheat, inducing significant yield losses and toxin accumulation in grains. Fungal pathogens responsible for HB include the genus Microdochium, with two species, and the toxin producer genus Fusarium, with several species. Field studies and surveys show that two or more species can coexist within a same field and coinfect the same plant or the same spike. In the current study, we investigated how the concomitant presence of F. graminearum and another of the HB complex species influences the spike colonization and the toxin production by the fungi. To study these interactions, 17 well-characterized isolates representing five species were inoculated alone or in pairs on wheat spikes in greenhouse and field experiments. The fungal DNA in the grains was estimated by quantitative PCR and toxin contents (deoxynivalenol and nivalenol) by ultraperformance liquid chromatography-UV detection-tandem mass spectrometry. The responses of the different isolates to the presence of a competitor were variable and isolate specific more than species specific. The development of the most aggressive isolates was either unchanged or a slightly increased, while the development of the less aggressive isolates was reduced. The main outcome of the study was that no trend of increased toxin production was observed in coinoculations compared to single inoculations. On the contrary, the amount of toxin produced was often lower than expected in coinoculations. We thus conclude against the hypothesis that the co-occurrence of several HB-causing species in the same field might aggravate the risk linked to fusarium toxins in wheat production. PMID:25416772

Characterization of Triticum aestivum Abscisic Acid Receptors and a Possible Role for These in Mediating Fusairum Head Blight Susceptibility in Wheat.

PubMed

Gordon, Cameron S; Rajagopalan, Nandhakishore; Risseeuw, Eddy P; Surpin, Marci; Ball, Fraser J; Barber, Carla J; Buhrow, Leann M; Clark, Shawn M; Page, Jonathan E; Todd, Chris D; Abrams, Suzanne R; Loewen, Michele C

2016-01-01

Abscisic acid (ABA) is a well-characterized plant hormone, known to mediate developmental aspects as well as both abiotic and biotic stress responses. Notably, the exogenous application of ABA has recently been shown to increase susceptibility to the fungal pathogen Fusarium graminearum, the causative agent of Fusarium head blight (FHB) in wheat and other cereals. However roles and mechanisms associated with ABA's modulation of pathogen responses remain enigmatic. Here the identification of putative ABA receptors from available genomic databases for Triticum aestivum (bread wheat) and Brachypodium distachyon (a model cereal) are reported. A number of these were cloned for recombinant expression and their functionality as ABA receptors confirmed by in vitro assays against protein phosphatases Type 2Cs. Ligand selectivity profiling of one of the wheat receptors (Ta_PYL2DS_FL) highlighted unique activities compared to Arabidopsis AtPYL5. Mutagenic analysis showed Ta_PYL2DS_FL amino acid D180 as being a critical contributor to this selectivity. Subsequently, a virus induced gene silencing (VIGS) approach was used to knockdown wheat Ta_PYL4AS_A (and similar) in planta, yielding plants with increased early stage resistance to FHB progression and decreased mycotoxin accumulation. Together these results confirm the existence of a family of ABA receptors in wheat and Brachypodium and present insight into factors modulating receptor function at the molecular level. That knockdown of Ta_PYL4AS_A (and similar) leads to early stage FHB resistance highlights novel targets for investigation in the future development of disease resistant crops.

Identification of Kernel Proteins Associated with the Resistance to Fusarium Head Blight in Winter Wheat (Triticum aestivum L.)

PubMed Central

Góral, Tomasz; Kwiatek, Michał; Majka, Maciej; Kosmala, Arkadiusz

2014-01-01

Numerous potential components involved in the resistance to Fusarium head blight (FHB) in cereals have been indicated, however, our knowledge regarding this process is still limited and further work is required. Two winter wheat (Triticum aestivum L.) lines differing in their levels of resistance to FHB were analyzed to identify the most crucial proteins associated with resistance in this species. The presented work involved analysis of protein abundance in the kernel bulks of more resistant and more susceptible wheat lines using two-dimensional gel electrophoresis and mass spectrometry identification of proteins, which were differentially accumulated between the analyzed lines, after inoculation with F. culmorum under field conditions. All the obtained two-dimensional patterns were demonstrated to be well-resolved protein maps of kernel proteomes. Although, 11 proteins were shown to have significantly different abundance between these two groups of plants, only two are likely to be crucial and have a potential role in resistance to FHB. Monomeric alpha-amylase and dimeric alpha-amylase inhibitors, both highly accumulated in the more resistant line, after inoculation and in the control conditions. Fusarium pathogens can use hydrolytic enzymes, including amylases to colonize kernels and acquire nitrogen and carbon from the endosperm and we suggest that the inhibition of pathogen amylase activity could be one of the most crucial mechanisms to prevent infection progress in the analyzed wheat line with a higher resistance. Alpha-amylase activity assays confirmed this suggestion as it revealed the highest level of enzyme activity, after F. culmorum infection, in the line more susceptible to FHB. PMID:25340555

Identification of kernel proteins associated with the resistance to fusarium head blight in winter wheat (Triticum aestivum L.).

PubMed

Perlikowski, Dawid; Wiśniewska, Halina; Góral, Tomasz; Kwiatek, Michał; Majka, Maciej; Kosmala, Arkadiusz

2014-01-01

Numerous potential components involved in the resistance to Fusarium head blight (FHB) in cereals have been indicated, however, our knowledge regarding this process is still limited and further work is required. Two winter wheat (Triticum aestivum L.) lines differing in their levels of resistance to FHB were analyzed to identify the most crucial proteins associated with resistance in this species. The presented work involved analysis of protein abundance in the kernel bulks of more resistant and more susceptible wheat lines using two-dimensional gel electrophoresis and mass spectrometry identification of proteins, which were differentially accumulated between the analyzed lines, after inoculation with F. culmorum under field conditions. All the obtained two-dimensional patterns were demonstrated to be well-resolved protein maps of kernel proteomes. Although, 11 proteins were shown to have significantly different abundance between these two groups of plants, only two are likely to be crucial and have a potential role in resistance to FHB. Monomeric alpha-amylase and dimeric alpha-amylase inhibitors, both highly accumulated in the more resistant line, after inoculation and in the control conditions. Fusarium pathogens can use hydrolytic enzymes, including amylases to colonize kernels and acquire nitrogen and carbon from the endosperm and we suggest that the inhibition of pathogen amylase activity could be one of the most crucial mechanisms to prevent infection progress in the analyzed wheat line with a higher resistance. Alpha-amylase activity assays confirmed this suggestion as it revealed the highest level of enzyme activity, after F. culmorum infection, in the line more susceptible to FHB.

Molecular interactions between tomato and the leaf mold pathogen Cladosporium fulvum.

PubMed

Rivas, Susana; Thomas, Colwyn M

2005-01-01

The interaction between tomato and the leaf mold pathogen Cladosporium fulvum is controlled in a gene-for-gene manner. This interaction has provided useful insights to the molecular basis of recognition specificity in plant disease resistance (R) proteins, disease resistance (R) gene evolution, R-protein mediated signaling, and cellular responses to pathogen attack. Tomato Cf genes encode type I membrane-associated receptor-like proteins (RLPs) comprised predominantly of extracellular leucine-rich repeats (eLRRs) and which are anchored in the plasma membrane. Cf proteins recognize fungal avirulence (Avr) peptides secreted into the leaf apoplast during infection. A direct interaction of Cf proteins with their cognate Avr proteins has not been demonstrated and the molecular mechanism of Avr protein perception is not known. Following ligand perception Cf proteins trigger a hypersensitive response (HR) and the arrest of pathogen development. Cf proteins lack an obvious signaling domain, suggesting that defense response activation is mediated through interactions with other partners. Avr protein perception results in the rapid accumulation of active oxygen species (AOS), changes in cellular ion fluxes, activation of protein kinase cascades, changes in gene expression and, possibly, targeted protein degradation. Here we review our current understanding of Cf-mediated responses in resistance to C. fulvum.

Biocontrol Potential of Streptomyces hydrogenans Strain DH16 toward Alternaria brassicicola to Control Damping Off and Black Leaf Spot of Raphanus sativus

PubMed Central

Manhas, Rajesh K.; Kaur, Talwinder

2016-01-01

Biocontrol agents and their bioactive metabolites provide one of the best alternatives to decrease the use of chemical pesticides. In light of this, the present investigation reports the biocontrol potential of Streptomyces hydrogenans DH16 and its metabolites towards Alternaria brassicicola, causal agent of black leaf spot and damping off of seedlings of crucifers. In vitro antibiosis of strain against pathogen revealed complete suppression of mycelial growth of pathogen, grown in potato dextrose broth supplemented with culture supernatant (20% v/v) of S. hydrogenans DH16. Microscopic examination of the fungal growth showed severe morphological abnormalities in the mycelium caused by antifungal metabolites. In vivo studies showed the efficacy of streptomycete cells and culture supernatant as seed dressings to control damping off of Raphanus sativus seedlings. Treatment of pathogen infested seeds with culture supernatant (10%) and streptomycete cells significantly improved seed germination (75–80%) and vigor index (1167–1538). Furthermore, potential of cells and culture supernatant as foliar treatment to control black leaf spot was also evaluated. Clearly visible symptoms of disease were observed in the control plants with 66.81% disease incidence and retarded growth of root system. However, disease incidence reduced to 6.78 and 1.47% in plants treated with antagonist and its metabolites, respectively. Additionally, treatment of seeds and plants with streptomycete stimulated various growth traits of plants over uninoculated control plants in the absence of pathogen challenge. These results indicate that S. hydrogenans and its culture metabolites can be developed as biofungicides as seed dressings to control seed borne pathogens, and as sprays to control black leaf spot of crucifers. PMID:28018402

What Causes a Blighted Ovum?

MedlinePlus

... ovum: What causes it? What causes a blighted ovum? What symptoms can I expect? Answers from Yvonne Butler Tobah, M.D. A blighted ovum, also called an anembryonic pregnancy or anembryonic gestation, ...

Mycosphaerella fijiensis, the black leaf streak pathogen of banana: progress towards understanding pathogen biology and detection, disease development, and the challenges of control.

PubMed

Churchill, Alice C L

2011-05-01

Banana (Musa spp.) is grown throughout the tropical and subtropical regions of the world. The fruits are a key staple food in many developing countries and a source of income for subsistence farmers. Bananas are also a major, multibillion-dollar export commodity for consumption primarily in developed countries, where few banana cultivars are grown. The fungal pathogen Mycosphaerella fijiensis causes black leaf streak disease (BLSD; aka black Sigatoka leaf spot) on the majority of edible banana cultivars grown worldwide. The fact that most of these cultivars are sterile and unsuitable for the breeding of resistant lines necessitates the extensive use of fungicides as the primary means of disease control. BLSD is a significant threat to the food security of resource-poor populations who cannot afford fungicides, and increases the environmental and health hazards where large-acreage monocultures of banana (Cavendish subgroup, AAA genome) are grown for export. Mycosphaerella fijiensis M. Morelet is a sexual, heterothallic fungus having Pseudocercospora fijiensis (M. Morelet) Deighton as the anamorph stage. It is a haploid, hemibiotrophic ascomycete within the class Dothideomycetes, order Capnodiales and family Mycosphaerellaceae. Its taxonomic placement is based on DNA phylogeny, morphological analyses and cultural characteristics. Mycosphaerella fijiensis is a leaf pathogen that causes reddish-brown streaks running parallel to the leaf veins, which aggregate to form larger, dark-brown to black compound streaks. These streaks eventually form fusiform or elliptical lesions that coalesce, form a water-soaked border with a yellow halo and, eventually, merge to cause extensive leaf necrosis. The disease does not kill the plants immediately, but weakens them by decreasing the photosynthetic capacity of leaves, causing a reduction in the quantity and quality of fruit, and inducing the premature ripening of fruit harvested from infected plants. Although Musa spp. are the primary hosts of M. fijiensis, the ornamental plant Heliconia psittacorum has been reported as an alternative host. Several valuable tools and resources have been developed to overcome some of the challenges of studying this host-pathogen system. These include a DNA-mediated fungal transformation system and the ability to conduct targeted gene disruptions, reliable quantitative plant bioassays, diagnostic probes to detect and differentiate M. fijiensis from related pathogens and to distinguish strains of different mating types, and a genome sequence that has revealed a wealth of gene sequences and molecular markers to be utilized in functional and population biology studies. http://bananas.bioversityinternational.org/, http://genome.jgi-psf.org/Mycfi2/Mycfi2.home.html, http://www.isppweb.org/names_banana_pathogen.asp#fun, http://www.promusa.org/. © 2010 THE AUTHOR. MOLECULAR PLANT PATHOLOGY © 2010 BSPP AND BLACKWELL PUBLISHING LTD.

Leaf physiology and biomass allocation of backcross hybrid American chestnut (Castanea dentata) seedlings in response to light and water availability.

PubMed

Brown, Caleb E; Mickelbart, Michael V; Jacobs, Douglass F

2014-12-01

Partial canopy cover promotes regeneration of many temperate forest trees, but the consequences of shading on seedling drought resistance are unclear. Reintroduction of blight-resistant American chestnut (Castanea dentata (Marsh.) Borkh.) into eastern North American forests will often occur on water-limited sites and under partial canopy cover. We measured leaf pre-dawn water potential (Ψpd), leaf gas exchange, and growth and biomass allocation of backcross hybrid American chestnut seedlings from three orchard sources grown under different light intensities (76, 26 and 8% full photosynthetically active radiation (PAR)) and subjected to well-watered or mid-season water-stressed conditions. Seedlings in the water-stress treatment were returned to well-watered conditions after wilting to examine recovery. Seedlings growing under medium- and high-light conditions wilted at lower leaf Ψpd than low-light seedlings. Recovery of net photosynthesis (Anet) and stomatal conductance (gs) was greater in low and medium light than in high light. Seed source did not affect the response to water stress or light level in most cases. Between 26 and 8% full PAR, light became limiting to the extent that the effects of water stress had no impact on some growth and morphological traits. We conclude that positive and negative aspects of shading on seedling drought tolerance and recovery are not mutually exclusive. Partial shade may help American chestnut tolerate drought during early establishment through effects on physiological conditioning. © The Author 2014. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Interactions involving ozone, Botrytis cinerea, and B. squamosa on onion leaves

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rist, D.L.

1983-01-01

Interactions involving Botrytis cinerea Pers., B. squamosa Walker, and ozone on onion (alium cepae L.) were investigated. Initially, threshold dosages of ozone required to predispose onion leaves to greater infection by B. cinerea and B. squamosa were determined under controlled conditions in an ozone-exposure chamber. Subsequent experiments supported the hypothesis that nutrients leaking out of ozone-injured cells stimulated lesion production by B. cinerea. The electrical conductivity of, and carbohydrate concentration in, dew collected from leaves of onion plants which had been exposed to ozone were greater than the electrical conductivity of, and carbohydrate concentration in, dew collected from leaves ofmore » other, non-exposed onion plants. When conidia of B. cinerea were suspended in dew collected from leaves of plants which had been exposed to ozone and the resulting suspension atomized onto leaves of non-exposed plants, more lesions were induced than on leaves of other non-exposed plants inoculated with conidia suspended in dew collected from plants which had not been exposed to ozone. EDU protected onion leaves from ozone-induced predisposition to these fungi under controlled conditions. Experiments designed to detect interaction between B. cinerea and B. squamosa in onion leaf blighting indicated that such interaction did not occur. Leaves were blighted rapidly when inoculated with B. squamosa whether B. cinerea was present or absent.« less

Correlation of isolability of the oak wilt pathogen with leaf wilt and vascular water flow resistance

Treesearch

Garold F. Gregory

1971-01-01

Isolations and water flow-rate measurements made on short stem sections of young red oak seedlings inoculated with the oak wilt pathogen, Ceratocystis fagacearum, about 1 to 2 inches above the soil line, revealed that the oak wilt pathogen was isolable first near the inoculation site. As time after inoculation increased, the pathogen was isolated...

Reduction of Escherichia coli O157:H7 on produce by use of electrolyzed water under simulated food service operation conditions.

PubMed

Pangloli, Philipus; Hung, Yen-Con; Beuchat, Larry R; King, C Harold; Zhao, Zhi-Hui

2009-09-01

Treatment of fresh fruits and vegetables with electrolyzed water (EW) has been shown to kill or reduce foodborne pathogens. We evaluated the efficacy of EW in killing Escherichia coli O157:H7 on iceberg lettuce, cabbage, lemons, and tomatoes by using washing and/or chilling treatments simulating those followed in some food service kitchens. Greatest reduction levels on lettuce were achieved by sequentially washing with 14-A (amperage) acidic EW (AcEW) for 15 or 30 s followed by chilling in 16-A AcEW for 15 min. This procedure reduced the pathogen by 2.8 and 3.0 log CFU per leaf, respectively, whereas washing and chilling with tap water reduced the pathogen by 1.9 and 2.4 log CFU per leaf. Washing cabbage leaves for 15 or 30 s with tap water or 14-A AcEW reduced the pathogen by 2.0 and 3.0 log CFU per leaf and 2.5 to 3.0 log CFU per leaf, respectively. The pathogen was reduced by 4.7 log CFU per lemon by washing with 14-A AcEW and 4.1 and 4.5 log CFU per lemon by washing with tap water for 15 or 30 s. A reduction of 5.3 log CFU per lemon was achieved by washing with 14-A alkaline EW for 15 s prior to washing with 14-A AcEW for 15 s. Washing tomatoes with tap water or 14-A AcEW for 15 s reduced the pathogen by 6.4 and 7.9 log CFU per tomato, respectively. Application of AcEW using procedures mimicking food service operations should help minimize cross-contamination and reduce the risk of E. coli O157:H7 being present on produce at the time of consumption.

Bacterial Leaf Scorch of Amenity Trees a Wide-Spread Problem of Economic Significance to the Urban Forest

Treesearch

James Lashomb; Alan Iskra; Ann Brooks Gould; George Hamilton

2003-01-01

Bacterial leaf scorch (BLS) of amenity trees is caused by the bacterium Xylella fastidiosa, a xylem-limited pathogen that causes water stress resulting in leaf scorch, decline, and eventual death of affected trees. Recent surveys indicate that BLS is widespread throughout the eastern half of the United States. In New Jersey, BLS primarily affects red and pin oaks...

Expression of apoplast-targeted plant defensin MtDef4.2 confers resistance to leaf rust pathogen Puccinia triticina but does not affect mycorrhizal symbiosis in transgenic wheat

USDA-ARS?s Scientific Manuscript database

Rust diseases caused by Puccinia spp. pose a major threat to global wheat production. Puccinia triticina (Pt), an obligate basidiomycete biotroph, causes leaf rust disease which incurs yield losses of up to 50% in wheat. Historically, resistant wheat cultivars have been used to control leaf rust, bu...

Lathyrus sativus transcriptome resistance response to Ascochyta lathyri investigated by deepSuperSAGE analysis

PubMed Central

Almeida, Nuno F.; Krezdorn, Nicolas; Rotter, Björn; Winter, Peter; Rubiales, Diego; Vaz Patto, Maria C.

2015-01-01

Lathyrus sativus (grass pea) is a temperate grain legume crop with a great potential for expansion in dry areas or zones that are becoming more drought-prone. It is also recognized as a potential source of resistance to several important diseases in legumes, such as ascochyta blight. Nevertheless, the lack of detailed genomic and/or transcriptomic information hampers further exploitation of grass pea resistance-related genes in precision breeding. To elucidate the pathways differentially regulated during ascochyta-grass pea interaction and to identify resistance candidate genes, we compared the early response of the leaf gene expression profile of a resistant L. sativus genotype to Ascochyta lathyri infection with a non-inoculated control sample from the same genotype employing deepSuperSAGE. This analysis generated 14.387 UniTags of which 95.7% mapped to a reference grass pea/rust interaction transcriptome. From the total mapped UniTags, 738 were significantly differentially expressed between control and inoculated leaves. The results indicate that several gene classes acting in different phases of the plant/pathogen interaction are involved in the L. sativus response to A. lathyri infection. Most notably a clear up-regulation of defense-related genes involved in and/or regulated by the ethylene pathway was observed. There was also evidence of alterations in cell wall metabolism indicated by overexpression of cellulose synthase and lignin biosynthesis genes. This first genome-wide overview of the gene expression profile of the L. sativus response to ascochyta infection delivered a valuable set of candidate resistance genes for future use in precision breeding. PMID:25852725

Etiology of bronze leaf disease of Populus

Treesearch

Jason A. Smith; R. A. Blanchette; M. E. Ostry; N. A. Anderson

2002-01-01

Bronze leaf disease is a potentially destructive disorder of the Populus section of the genus Populus. The causal agent has been reported to be Apioplagiostoma populi (anarnorph: Discula sp.). Based on etiological and symptomological studies, field observations of symptom development suggest that the pathogen...

Survival, dispersal, and potential soil-mediated suppression of Phytophthora ramorum in a California redwood-tanoak forest.

PubMed

Fichtner, E J; Lynch, S C; Rizzo, D M

2009-05-01

Because the role of soil inoculum of Phytophthora ramorum in the sudden oak death disease cycle is not well understood, this work addresses survival, chlamydospore production, pathogen suppression, and splash dispersal of the pathogen in infested forest soils. Colonized rhododendron and bay laurel leaf disks were placed in mesh sachets before transfer to the field in January 2005 and 2006. Sachets were placed under tanoak, bay laurel, and redwood at three vertical locations: leaf litter surface, litter-soil interface, and below the soil surface. Sachets were retrieved after 4, 8, 20, and 49 weeks. Pathogen survival was higher in rhododendron leaf tissue than in bay tissue, with >80% survival observed in rhododendron tissue after 49 weeks in the field. Chlamydospore production was determined by clearing infected tissue in KOH. Moist redwood-associated soils suppressed chlamydospore production. Rain events splashed inoculum as high as 30 cm from the soil surface, inciting aerial infection of bay laurel and tanoak. Leaf litter may provide an incomplete barrier to splash dispersal. This 2-year study illustrates annual P. ramorum survival in soil and the suppressive nature of redwood-associated soils to chlamydospore production. Infested soil may serve as primary inoculum for foliar infections by splash dispersal during rain events.

Inhibitory effect of Xenorhabdus nematophila TB on plant pathogens Phytophthora capsici and Botrytis cinerea in vitro and in planta

PubMed Central

Fang, Xiangling; Zhang, Manrang; Tang, Qian; Wang, Yonghong; Zhang, Xing

2014-01-01

Entomopathogenic bacteria Xenorhabdus spp. produce secondary metabolites with potential antimicrobial activity for use in agricultural productions. This study evaluated the inhibitory effect of X. nematophila TB culture on plant pathogens Botrytis cinerea and Phytophthora capsici. The cell-free filtrate of TB culture showed strong inhibitory effects (>90%) on mycelial growth of both pathogens. The methanol-extracted bioactive compounds (methanol extract) of TB culture also had strong inhibitory effects on mycelial growth and spore germinations of both pathogens. The methanol extract (1000 μg/mL) and cell-free filtrate both showed strong therapeutic and protective effects (>70%) on grey mold both in detached tomato fruits and plants, and leaf scorch in pepper plants. This study demonstrates X. nematophila TB produces antimicrobial metabolites of strong activity on plant pathogens, with great potential for controlling tomato grey mold and pepper leaf scorch and being used in integrated disease control to reduce chemical application. PMID:24599183

Inhibitory effect of Xenorhabdus nematophila TB on plant pathogens Phytophthora capsici and Botrytis cinerea in vitro and in planta.

PubMed

Fang, Xiangling; Zhang, Manrang; Tang, Qian; Wang, Yonghong; Zhang, Xing

2014-03-06

Entomopathogenic bacteria Xenorhabdus spp. produce secondary metabolites with potential antimicrobial activity for use in agricultural productions. This study evaluated the inhibitory effect of X. nematophila TB culture on plant pathogens Botrytis cinerea and Phytophthora capsici. The cell-free filtrate of TB culture showed strong inhibitory effects (>90%) on mycelial growth of both pathogens. The methanol-extracted bioactive compounds (methanol extract) of TB culture also had strong inhibitory effects on mycelial growth and spore germinations of both pathogens. The methanol extract (1000 μg/mL) and cell-free filtrate both showed strong therapeutic and protective effects (>70%) on grey mold both in detached tomato fruits and plants, and leaf scorch in pepper plants. This study demonstrates X. nematophila TB produces antimicrobial metabolites of strong activity on plant pathogens, with great potential for controlling tomato grey mold and pepper leaf scorch and being used in integrated disease control to reduce chemical application.

First Report of Leaf Spot Caused by Alternaria tenuissima on Black Chokeberry (Aronia melanocarpa) in Korea.

PubMed

Wee, Jung-In; Park, Jong-Han; Back, Chang-Gi; You, Young-Hyun; Chang, Taehyun

2016-09-01

In July 2015, diseased leaves of black chokeberry ( Aronia melanocarpa ) were observed in Danyang and Gochang, Korea. The symptoms appeared as circular or irregular brown leaf spots, from which Alternaria tenuissima was isolated. The isolates were cultured on potato dextrose agar, and their morphological characteristics were observed under a light microscope. The colonies were whitish to ash colored. The pathogenicity test on healthy black chokeberry leaves produced circular brown spots, in line with the original symptoms. Molecular analyses of the ITS, GPD, RPB2, and TEF genes were conducted to confirm the identity of the pathogen. The phylogeny of the multi-gene sequences indicated that the causal agent was A. tenuissima . This study is the first report of A. tenuissima leaf spot on black chokeberry ( A. melanocarpa ).

Pyramiding transgenes for multiple resistance in rice against bacterial blight, yellow stem borer and sheath blight.

PubMed

Datta, K; Baisakh, N; Thet, K Maung; Tu, J; Datta, S K

2002-12-01

Here we describe the development of transgene-pyramided stable elite rice lines resistant to disease and insect pests by conventional crossing of two transgenic parental lines transformed independently with different genes. The Xa21 gene (resistance to bacterial blight), the Bt fusion gene (for insect resistance) and the chitinase gene (for tolerance of sheath blight) were combined in a single rice line by reciprocal crossing of two transgenic homozygous IR72 lines. F4 plant lines carrying all the genes of interest stably were identified using molecular methods. The identified lines, when exposed to infection caused by Xanthomonas oryzae pv oryzae, showed resistance to bacterial blight. Neonate larval mortality rates of yellow stem borer ( Scirpophaga incertulas) in an insect bioassay of the same identified lines were 100%. The identified line pyramided with different genes to protect against yield loss showed high tolerance of sheath blight disease caused by Rhizoctonia solani.

Leaf spot disease adversely affects human health-promoting constituents and withanolide biosynthesis in Withania somnifera (L.) Dunal.

PubMed

Singh, V; Singh, B; Sharma, A; Kaur, K; Gupta, A P; Salar, R K; Hallan, V; Pati, P K

2017-01-01

The present work investigates the implication of leaf spot disease on the antioxidant potential and commercial value of pharmaceutically important constituents of Withania somnifera, a high-valued medicinal plant. Leaf spot disease was induced in W. somnifera by inoculating Alternaria alternata (Fr.) Keiss. pathogen. Total polyphenolic content and antioxidant potential showed a significant decrease during leaf spot disease. Evaluation of pharmaceutically active constituents withaferin A, withanone and withanolide A utilizing high-performance liquid chromatography showed a significant decrease in diseased samples as compared to healthy ones. Quantitative expression of major genes involved in withanolide biosynthesis also showed down-regulation in diseased samples. Alterations in the ultra-structure of chloroplasts were also analysed under transmission electron microscopy to get a better insight into the changes of withanolide biosynthesis in leaf during disease infestation. The present work suggests that when the pathogenic fungus invades the host plants, it evokes multiple responses, which could be studied at various levels. The knowledge gained from this work will provide appropriate rationale for controlling the bio-deterioration of the pharmaceutically active metabolites in W. somnifera and development of suitable strategies against leaf spot disease. This is the first study to investigate the effect of leaf spot disease on the human health-promoting constituents and withanolide biosynthesis in this high-valued medicinal plant. © 2016 The Society for Applied Microbiology.

A nitrogen response pathway regulates virulence in plant pathogenic fungi: role of TOR and the bZIP protein MeaB.

PubMed

López-Berges, Manuel S; Rispail, Nicolas; Prados-Rosales, Rafael C; Di Pietro, Antonio

2010-12-01

Virulence in plant pathogenic fungi is controlled through a variety of cellular pathways in response to the host environment. Nitrogen limitation has been proposed to act as a key signal to trigger the in planta expression of virulence genes. Moreover, a conserved Pathogenicity mitogen activated protein kinase (MAPK) cascade is strictly required for plant infection in a wide range of pathogens. We investigated the relationship between nitrogen signaling and the Pathogenicity MAPK cascade in controlling infectious growth of the vascular wilt fungus Fusarium oxysporum. Several MAPK-activated virulence functions such as invasive growth, vegetative hyphal fusion and host adhesion were strongly repressed in the presence of the preferred nitrogen source ammonium. Repression of these functions by ammonium was abolished by L-Methionine sulfoximine (MSX) or rapamycin, two specific inhibitors of Gln synthetase and the protein kinase TOR (Target Of Rapamycin), respectively, and was dependent on the bZIP protein MeaB. Supplying tomato plants with ammonium rather than nitrate resulted in a significant delay of vascular wilt symptoms caused by the F. oxysporum wild type strain, but not by the ΔmeaB mutant. Ammonium also repressed invasive growth in two other pathogens, the rice blast fungus Magnaporthe oryzae and the wheat head blight pathogen Fusarium graminearum. Our results suggest the presence of a conserved nitrogen-responsive pathway that operates via TOR and MeaB to control infectious growth in plant pathogenic fungi.

Genetic diversity of Fusarium graminearum sensu lato isolates from wheat associated with Fusarium Head Blight in diverse geographic locations of Argentina.

PubMed

Consolo, Verónica F; Ortega, Leonel M; Salerno, Graciela; Astoreca, Andrea L; Alconada, Teresa M

2015-01-01

Fusarium Head Blight is an important wheat disease in the Argentine Pampas region, being Fusarium graminearum the predominant pathogen. DNA polymorphism of the isolates was analyzed by IGS-RFLP and ISSR. IGS-RFLP and ISSR profiling were carried out using six endonucleases and eight primers, respectively. IGS-RFLP yielded 41 bands, 30 of which were polymorphic while ISSR produced 87 bands with 47 polymorphic bands. Both markers showed genetic variability among the analyzed isolates; however, IGS-RFLP was more efficient than ISSR, showing a higher polymorphic average (59.91%) than the latter (44.11%). The averages of polymorphic information content (PIC) were 0.211 and 0.129, respectively. Twenty haplotypes were identified by IGS-RFLP and 15 haplotypes by ISSR. Genotype clustering within dendrograms was different for both types of markers. The genetic groups obtained by IGS-RFLP showed a partial association to geographic origin. This is the first report on genetic variability of F. graminearum isolates from wheat in Argentina using IGS-RFLP and ISSR markers. Copyright © 2015 Asociación Argentina de Microbiología. Publicado por Elsevier España, S.L.U. All rights reserved.

Changes in Cryphonectria parasitica Populations Affect Natural Biological Control of Chestnut Blight.

PubMed

Ježić, Marin; Mlinarec, Jelena; Vuković, Rosemary; Katanić, Zorana; Krstin, Ljiljana; Nuskern, Lucija; Poljak, Igor; Idžojtić, Marilena; Tkalec, Mirta; Ćurković-Perica, Mirna

2018-07-01

Invasive species, especially plant pathogens, have a potential to completely eradicate native plant species and remodel landscapes. Tripartite interactions among sweet chestnut (Castanea sativa), chestnut blight-causing invasive fungus Cryphonectria parasitica, and hyperparasitic virus Cryphonectria hypovirus 1 (CHV1) were studied in two populations. The number of different vegetative compatibility (vc) types of C. parasitica more than doubled over the 10 years, while the hypovirulence incidence dropped in one population and slightly increased in the other one. Over the course of our 3-year monitoring experiment, the prevalence of hypovirulent isolates obtained from monitored cankers increased slowly (i.e., more hypovirulent isolates were being obtained from the same cankers over time). Within studied cankers, considerable changes in vc type and CHV1 presence were observed, indicating a highly dynamic system in which virulent and hypovirulent mycelia, sometimes of discordant vc types, often appeared together. The increase in hypovirulence prevalence did not have any observable curative effect on the cankers and, occasionally, reactivation of healed cankers by new, virulent C. parasitica isolates was observed. Both short- and long-term observations and revalidation of the infected plant populations are necessary to accurately estimate disease progress and formulate an adequate disease management strategy.

Sexually mature transgenic American chestnut trees via embryogenic suspension-based transformation.

PubMed

Andrade, Gisele M; Nairn, Campbell J; Le, Huong T; Merkle, Scott A

2009-09-01

The availability of a system for direct transfer of anti-fungal candidate genes into American chestnut (Castanea dentata), devastated by a fungal blight in the last century, would offer an alternative or supplemental approach to conventional breeding for production of chestnut trees resistant to the blight fungus and other pathogens. By taking advantage of the strong ability of embryogenic American chestnut cultures to proliferate in suspension, a high-throughput Agrobacterium tumefaciens-mediated transformation protocol for stable integration of foreign genes into the tree was established. Proembryogenic masses (PEMs) were co-cultivated with A. tumefaciens strain AGL1 harboring the plasmid pCAMBIA 2301, followed by stringent selection with 50 or 100 mg/l Geneticin. A protocol employing size-fractionation to enrich for small PEMs to use as target material and selection in suspension culture was applied to rapidly produce transgenic events with an average efficiency of four independent transformation events per 50 mg of target tissue and minimal escapes. Mature somatic embryos, representing 18 transgenic events and derived from multiple American chestnut target genotypes, were germinated and over 100 transgenic somatic seedlings were produced and acclimatized to greenhouse conditions. Multiple vigorous transgenic somatic seedlings produced functional staminate flowers within 3 years following regeneration.

Bacterial Leaf Spot of Lettuce: Request for Samples

USDA-ARS?s Scientific Manuscript database

Bacterial leaf spot of lettuce caused by by Xanthomonas campestris pv. vitians has been affecting coastal California crops for many years and has become a chronic problem. Differences in pathogen genotypes have been demonstrated and correlated to disease responses on resistant and susceptible cultiv...

Bacterial Leaf Spot of Parsley: Characterization of a New Disease

USDA-ARS?s Scientific Manuscript database

Since 2002, a severe leaf spot disease on parsley has occurred throughout central coastal California and particularly in Monterey County. Two different bacterial pathogens (Pseudomonas syringae pv. apii, and P. syringae pv. coriandricola) have been associated these outbreaks on parsley. Our research...

Root treatment with rhizobacteria antagonistic to Phytophthora blight affects anthracnose occurrence, ripening, and yield of pepper fruit in the plastic house and field.

PubMed

Sang, Mee Kyung; Kim, Jeong Do; Kim, Beom Seok; Kim, Ki Deok

2011-06-01

We previously selected rhizobacterial strains CCR04, CCR80, GSE09, ISE13, and ISE14, which were antagonistic to Phytophthora blight of pepper. In this study, we investigated the effects of root treatment of rhizobacteria on anthracnose occurrence, ripening, and yield of pepper fruit in the plastic house and field in 2008 and 2009. We also examined the effects of volatiles produced by the strains on fruit ripening and on mycelial growth and spore development of Colletotrichum acutatum and Phytophthora capsici in the laboratory, identifying the volatile compounds by gas chromatography-mass spectrometry (GC-MS). In the house tests, all strains significantly (P < 0.05) reduced anthracnose incidence on pepper fruit; strains GSE09 and ISE14 consistently produced higher numbers of pepper fruit or increased the fresh weight of red fruit more than the controls in both years. In the field tests, all strains significantly (P < 0.05) reduced anthracnose occurrence on either green or red pepper fruit; strain ISE14 consistently produced higher numbers or increased fresh weights of red fruit more than the controls in both years. In the laboratory tests, volatiles produced by strains GSE09 and ISE13 only stimulated maturation of pepper fruit from green (unripe) to red (ripe) fruit; the volatiles of certain strains inhibited the growth and development of C. acutatum and P. capsici. On the other hand, GC-MS analysis of volatiles of strains GSE09 and ISE13 revealed 17 distinct compounds in both strains, including decane, dodecane, 1,3-di-tert-butylbenzene, tetradecane, 2,4-di-tert-butylphenol, and hexadecane. Among these compounds, 2,4-di-tert-butylphenol only stimulated fruit ripening and inhibited growth and development of the pathogens. Taken together, strains GSE09 and ISE14 effectively reduced anthracnose occurrence and stimulated pepper fruit ripening and yield, possibly via bacterial volatiles. Therefore, these two strains could be potential agents for controlling Phytophthora blight and anthracnose, and for increasing fruit ripening and yield. To our knowledge, this is the first report of volatiles such as 2,4-di-tert-butylphenol produced by rhizobacteria being related to both fruit ripening and pathogen inhibition.

Transgenic apple plants overexpressing the chalcone 3-hydroxylase gene of Cosmos sulphureus show increased levels of 3-hydroxyphloridzin and reduced susceptibility to apple scab and fire blight.

PubMed

Hutabarat, Olly Sanny; Flachowsky, Henryk; Regos, Ionela; Miosic, Silvija; Kaufmann, Christine; Faramarzi, Shadab; Alam, Mohammed Zobayer; Gosch, Christian; Peil, Andreas; Richter, Klaus; Hanke, Magda-Viola; Treutter, Dieter; Stich, Karl; Halbwirth, Heidi

2016-05-01

Overexpression of chalcone-3-hydroxylase provokes increased accumulation of 3-hydroxyphloridzin in Malus . Decreased flavonoid concentrations but unchanged flavonoid class composition were observed. The increased 3-hydroxyphlorizin contents correlate well with reduced susceptibility to fire blight and scab. The involvement of dihydrochalcones in the apple defence mechanism against pathogens is discussed but unknown biosynthetic steps in their formation hamper studies on their physiological relevance. The formation of 3-hydroxyphloretin is one of the gaps in the pathway. Polyphenol oxidases and cytochrome P450 dependent enzymes could be involved. Hydroxylation of phloretin in position 3 has high similarity to the B-ring hydroxylation of flavonoids catalysed by the well-known flavonoid 3'-hydroxylase (F3'H). Using recombinant F3'H and chalcone 3-hydroxylase (CH3H) from Cosmos sulphureus we show that F3'H and CH3H accept phloretin to some extent but higher conversion rates are obtained with CH3H. To test whether CH3H catalyzes the hydroxylation of dihydrochalcones in planta and if this could be of physiological relevance, we created transgenic apple trees harbouring CH3H from C. sulphureus. The three transgenic lines obtained showed lower polyphenol concentrations but no shift between the main polyphenol classes dihydrochalcones, flavonols, hydroxycinnamic acids and flavan 3-ols. Increase of 3-hydroxyphloridzin within the dihydrochalcones and of epicatechin/catechin within soluble flavan 3-ols were observed. Decreased activity of dihydroflavonol 4-reductase and chalcone synthase/chalcone isomerase could partially explain the lower polyphenol concentrations. In comparison to the parent line, the transgenic CH3H-lines showed a lower disease susceptibility to fire blight and apple scab that correlated with the increased 3-hydroxyphlorizin contents.

Identification of QTL conferring resistance to stripe rust (Puccinia striiformis f. sp. hordei) and leaf rust (Puccinia hordei) in barley using nested association mapping (NAM)

PubMed Central

Vatter, Thomas; Maurer, Andreas; Perovic, Dragan; Kopahnke, Doris; Pillen, Klaus

2018-01-01

The biotrophic rust fungi Puccinia hordei and Puccinia striiformis are important barley pathogens with the potential to cause high yield losses through an epidemic spread. The identification of QTL conferring resistance to these pathogens is the basis for targeted breeding approaches aiming to improve stripe rust and leaf rust resistance of modern cultivars. Exploiting the allelic richness of wild barley accessions proved to be a valuable tool to broaden the genetic base of resistance of barley cultivars. In this study, SNP-based nested association mapping (NAM) was performed to map stripe rust and leaf rust resistance QTL in the barley NAM population HEB-25, comprising 1,420 lines derived from BC1S3 generation. By scoring the percentage of infected leaf area, followed by calculation of the area under the disease progress curve and the average ordinate during a two-year field trial, a large variability of resistance across and within HEB-25 families was observed. NAM based on 5,715 informative SNPs resulted in the identification of twelve and eleven robust QTL for resistance against stripe rust and leaf rust, respectively. Out of these, eight QTL for stripe rust and two QTL for leaf rust are considered novel showing no overlap with previously reported resistance QTL. Overall, resistance to both pathogens in HEB-25 is most likely due to the accumulation of numerous small effect loci. In addition, the NAM results indicate that the 25 wild donor QTL alleles present in HEB-25 strongly differ in regard to their individual effect on rust resistance. In future, the NAM concept will allow to select and combine individual wild barley alleles from different HEB parents to increase rust resistance in barley. The HEB-25 results will support to unravel the genetic basis of rust resistance in barley, and to improve resistance against stripe rust and leaf rust of modern barley cultivars. PMID:29370232

Identification of QTL conferring resistance to stripe rust (Puccinia striiformis f. sp. hordei) and leaf rust (Puccinia hordei) in barley using nested association mapping (NAM).

PubMed

Vatter, Thomas; Maurer, Andreas; Perovic, Dragan; Kopahnke, Doris; Pillen, Klaus; Ordon, Frank

2018-01-01

The biotrophic rust fungi Puccinia hordei and Puccinia striiformis are important barley pathogens with the potential to cause high yield losses through an epidemic spread. The identification of QTL conferring resistance to these pathogens is the basis for targeted breeding approaches aiming to improve stripe rust and leaf rust resistance of modern cultivars. Exploiting the allelic richness of wild barley accessions proved to be a valuable tool to broaden the genetic base of resistance of barley cultivars. In this study, SNP-based nested association mapping (NAM) was performed to map stripe rust and leaf rust resistance QTL in the barley NAM population HEB-25, comprising 1,420 lines derived from BC1S3 generation. By scoring the percentage of infected leaf area, followed by calculation of the area under the disease progress curve and the average ordinate during a two-year field trial, a large variability of resistance across and within HEB-25 families was observed. NAM based on 5,715 informative SNPs resulted in the identification of twelve and eleven robust QTL for resistance against stripe rust and leaf rust, respectively. Out of these, eight QTL for stripe rust and two QTL for leaf rust are considered novel showing no overlap with previously reported resistance QTL. Overall, resistance to both pathogens in HEB-25 is most likely due to the accumulation of numerous small effect loci. In addition, the NAM results indicate that the 25 wild donor QTL alleles present in HEB-25 strongly differ in regard to their individual effect on rust resistance. In future, the NAM concept will allow to select and combine individual wild barley alleles from different HEB parents to increase rust resistance in barley. The HEB-25 results will support to unravel the genetic basis of rust resistance in barley, and to improve resistance against stripe rust and leaf rust of modern barley cultivars.

Bacteria in the Leaf Ecosystem with Emphasis on Pseudomonas syringae—a Pathogen, Ice Nucleus, and Epiphyte

PubMed Central

Hirano, Susan S.; Upper, Christen D.

2000-01-01

The extremely large number of leaves produced by terrestrial and aquatic plants provide habitats for colonization by a diversity of microorganisms. This review focuses on the bacterial component of leaf microbial communities, with emphasis on Pseudomonas syringae—a species that participates in leaf ecosystems as a pathogen, ice nucleus, and epiphyte. Among the diversity of bacteria that colonize leaves, none has received wider attention than P. syringae, as it gained notoriety for being the first recombinant organism (Ice− P. syringae) to be deliberately introduced into the environment. We focus on P. syringae to illustrate the attractiveness and somewhat unique opportunities provided by leaf ecosystems for addressing fundamental questions of microbial population dynamics and mechanisms of plant-bacterium interactions. Leaf ecosystems are dynamic and ephemeral. The physical environment surrounding phyllosphere microbes changes continuously with daily cycles in temperature, radiation, relative humidity, wind velocity, and leaf wetness. Slightly longer-term changes occur as weather systems pass. Seasonal climatic changes impose still a longer cycle. The physical and physiological characteristics of leaves change as they expand, mature, and senesce and as host phenology changes. Many of these factors influence the development of populations of P. syringae upon populations of leaves. P. syringae was first studied for its ability to cause disease on plants. However, disease causation is but one aspect of its life strategy. The bacterium can be found in association with healthy leaves, growing and surviving for many generations on the surfaces of leaves as an epiphyte. A number of genes and traits have been identified that contribute to the fitness of P. syringae in the phyllosphere. While still in their infancy, such research efforts demonstrate that the P. syringae-leaf ecosystem is a particularly attractive system with which to bridge the gap between what is known about the molecular biology of genes linked to pathogenicity and the ecology and epidemiology of associated diseases as they occur in natural settings, the field. PMID:10974129

Diverse mechanisms shape the evolution of virulence factors in the potato late blight pathogen Phytophthora infestans sampled from China

PubMed Central

Wu, E-Jiao; Yang, Li-Na; Zhu, Wen; Chen, Xiao-Mei; Shang, Li-Ping; Zhan, Jiasui

2016-01-01

Evolution of virulence in plant pathogens is still poorly understood but the knowledge is important for the effective use of plant resistance and sustainable disease management. Spatial population dynamics of virulence, race and SSR markers in 140 genotypes sampled from seven geographic locations in China were compared to infer the mechanisms driving the evolution of virulence in Phytophthora infestans (P. infestans). All virulence types and a full spectrum of race complexity, ranging from the race able to infect the universally susceptible cultivar only to all differentials, were detected. Eight and two virulence factors were under diversifying and constraining selection respectively while no natural selection was detected in one of the virulence types. Further analyses revealed excesses in simple and complex races but deficiency in intermediate race and negative associations of annual mean temperature at the site from which pathogen isolates were collected with frequency of virulence to differentials and race complexity in the pathogen populations. These results suggest that host selection may interact with other factors such as climatic conditions in determining the evolutionary trajectory of virulence and race structure in P. infestans and global warming may slow down the emergence of new virulence in the pathogen. PMID:27193142

Morphological characterization of several strains of the rice-pathogenic bacterium Burkholderia glumae in North Sumatra

NASA Astrophysics Data System (ADS)

Hasibuan, M.; Safni, I.; Lisnawita; Lubis, K.

2018-02-01

Burkholderia glumae is a quarantine seed-borne bacterial pathogen causing panicle blight disease on rice. This pathogen has been detected in some locations in Java, and recently, farmers in North Sumatra have reported rice yield loss with symptoms similar with those on rice infeced by the rice-pathogenic bacterium B. glumae. This research was aimed to isolate several bacterial strains from several rice varieties in various locations in North Sumatra and characterize the morphology of the strains to detect and identify the unknown bacterial strains presumably B. glumae. Several rice seed varieties were collected from Medan and Deli Serdang Districts. The seed samples were extracted, isolated and purified, then grown in semi-selective media PPGA. The morphological characteristics of the bacterial strains were determined including Gram staining, bacterial colony’s and bacterial cell’s morphology. The results showed that of eleven strains isolated, two strains were Gram negative and nine strains were Gram positive. On the basis of colony morphology, all strains had circular form, flat elevation and cream colour while the colony margin varied, i.e. entire and undulate. Most strains had bacillus/rod shape (8 strains) and only 3 strains were coccus.

Microbial Inhibition of Fusarium Pathogens and Biological Modification of Trichothecenes in Cereal Grains

PubMed Central

Wachowska, Urszula; Packa, Danuta

2017-01-01

Fungi of the genus Fusarium infect cereal crops during the growing season and cause head blight and other diseases. Their toxic secondary metabolites (mycotoxins) contaminate grains. Several dozen toxic compounds produced by fungal pathogens have been identified to date. Type B trichothecenes—deoxynivalenol, its acetyl derivatives and nivalenol (produced mainly by F. graminearum and F. culmorum)—are most commonly detected in cereal grains. “T-2 toxin” (produced by, among others, F. sporotrichioides) belongs to type-A trichothecenes which are more toxic than other trichothecenes. Antagonistic bacteria and fungi can affect pathogens of the genus Fusarium via different modes of action: direct (mycoparasitism or hyperparasitism), mixed-path (antibiotic secretion, production of lytic enzymes) and indirect (induction of host defense responses). Microbial modification of trichothecenes involves acetylation, deacetylation, oxidation, de-epoxidation, and epimerization, and it lowers the pathogenic potential of fungi of the genus Fusarium. Other modifing mechanisms described in the paper involve the physical adsorption of mycotoxins in bacterial cells and the conjugation of mycotoxins to glucose and other compounds in plant and fungal cells. The development of several patents supports the commercialization and wider application of microorganisms biodegrading mycotoxins in grains and, consequently, in feed additives. PMID:29261142

Three-Dimension Visualization for Primary Wheat Diseases Based on Simulation Model

NASA Astrophysics Data System (ADS)

Shijuan, Li; Yeping, Zhu

Crop simulation model has been becoming the core of agricultural production management and resource optimization management. Displaying crop growth process makes user observe the crop growth and development intuitionisticly. On the basis of understanding and grasping the occurrence condition, popularity season, key impact factors for main wheat diseases of stripe rust, leaf rust, stem rust, head blight and powdery mildew from research material and literature, we designed 3D visualization model for wheat growth and diseases occurrence. The model system will help farmer, technician and decision-maker to use crop growth simulation model better and provide decision-making support. Now 3D visualization model for wheat growth on the basis of simulation model has been developed, and the visualization model for primary wheat diseases is in the process of development.

Walnut (Juglans).

PubMed

Leslie, Charles A; Walawage, Sriema L; Uratsu, Sandra L; McGranahan, Gale; Dandekar, Abhaya M

2015-01-01

Walnut species are important nut and timber producers in temperate regions of Europe, Asia, South America, and North America. Trees can be impacted by Phytophthora, crown gall, nematodes, Armillaria, and cherry leaf roll virus; nuts can be severely damaged by codling moth, husk fly, and Xanthomonas blight. The long generation time of walnuts and an absence of identified natural resistance for most of these problems suggest biotechnological approaches to crop improvement. Described here is a somatic embryo-based transformation protocol that has been used to successfully insert horticulturally useful traits into walnut. Selection is based on the combined use of the selectable neomycin phosphotransferase (nptII) gene and the scorable uidA gene. Transformed embryos can be germinated or micropropagated and rooted for plant production. The method described has been used to establish field trials of mature trees.

Potential of Trichoderma harzianum for control of banana leaf fungal pathogens when applied with a food source and an organic adjuvant.

PubMed

Samuelian, Suren

2016-06-01

Trichoderma isolates were obtained from diseased leaves and fruit collected from plantations in the main banana production area in Northern Queensland. Phylogenetic analyses identified the Trichoderma isolates as T. harzianum and T. virens. The Trichoderma spp. were found to be antagonistic against the banana leaf pathogens Mycosphaerella musicola, Cordana musae, and Deightoniella torulosa in vitro. Several products used by the banana industry to increase production, including molasses, Fishoil and Seasol, were tested as food source for the Trichoderma isolates. The optimal food substrate was found to be molasses at a concentration of 5 %, which when used in combination with a di-1-p-menthene spreader-sticker enhanced the survivability of Trichoderma populations under natural conditions. This formulation suppressed D. torulosa development under glasshouse conditions. Furthermore, high sensitivity was observed towards the protectant fungicide Mancozeb but Biopest oil ® , a paraffinic oil, only marginally suppressed the growth of Trichoderma isolates in vitro. Thus, this protocol represents a potential to manage banana leaf pathogens as a part of an integrated disease approach.

Assessment of the antimobial activity of olive leaf extract against foodborne bacterial pathogens

USDA-ARS?s Scientific Manuscript database

Olive leaf extract (OLE) has been used traditionally as an herbal supplement since it contains polyphenolic compounds with beneficial properties ranging from increasing energy levels, lowering blood pressure, and supporting the cardiovascular and immune systems. In addition to the beneficial effect...

Potassium influences forage bermudagrass yield and fungal leaf disease severity in Mississippi

USDA-ARS?s Scientific Manuscript database

Leaf spot diseases are associated with K deficiency in forage bermudagrass. In 2010, a natural disease epiphytotic caused by six species of Bipolaris, Curvularia, and Exserohilum (dematiaceous hyphomycetes) was evaluated in 56 plots of ‘Tifton 44' bermudagrass in Mississippi. Pathogen occurrence, di...

Degradation of the benzoxazolinone class of phytoalexins is important for virulence of Fusarium pseudograminearum towards wheat.

PubMed

Kettle, Andrew J; Batley, Jacqueline; Benfield, Aurelie H; Manners, John M; Kazan, Kemal; Gardiner, Donald M

2015-12-01

Wheat, maize, rye and certain other agriculturally important species in the Poaceae family produce the benzoxazolinone class of phytoalexins on pest and pathogen attack. Benzoxazolinones can inhibit the growth of pathogens. However, certain fungi can actively detoxify these compounds. Despite this, a clear link between the ability to detoxify benzoxazolinones and pathogen virulence has not been shown. Here, through comparative genome analysis of several Fusarium species, we have identified a conserved genomic region around the FDB2 gene encoding an N-malonyltransferase enzyme known to be involved in benzoxazolinone degradation in the maize pathogen Fusarium verticillioides. Expression analyses demonstrated that a cluster of nine genes was responsive to exogenous benzoxazolinone in the important wheat pathogen Fusarium pseudograminearum. The analysis of independent F. pseudograminearum FDB2 knockouts and complementation of the knockout with FDB2 homologues from F. graminearum and F. verticillioides confirmed that the N-malonyltransferase enzyme encoded by this gene is central to the detoxification of benzoxazolinones, and that Fdb2 contributes quantitatively to virulence towards wheat in head blight inoculation assays. This contrasts with previous observations in F. verticillioides, where no effect of FDB2 mutations on pathogen virulence towards maize was observed. Overall, our results demonstrate that the detoxification of benzoxazolinones is a strategy adopted by wheat-infecting F. pseudograminearum to overcome host-derived chemical defences. © 2015 BSPP AND JOHN WILEY & SONS LTD.

Structural Characterization of Core Region in Erwinia amylovora Lipopolysaccharide.

PubMed

Casillo, Angela; Ziaco, Marcello; Lindner, Buko; Merino, Susana; Mendoza-Barberá, Elena; Tomás, Juan M; Corsaro, Maria Michela

2017-03-04

Erwinia amylovora ( E. amylovora ) is the first bacterial plant pathogen described and demonstrated to cause fire blight, a devastating plant disease affecting a wide range of species including a wide variety of Rosaceae . In this study, we reported the lipopolysaccharide (LPS) core structure from E. amylovora strain CFBP1430, the first one for an E. amylovora highly pathogenic strain. The chemical characterization was performed on the mutants waaL (lacking only the O-antigen LPS with a complete LPS-core), wabH and wabG (outer-LPS core mutants). The LPSs were isolated from dry cells and analyzed by means of chemical and spectroscopic methods. In particular, they were subjected to a mild acid hydrolysis and/or a hydrazinolysis and investigated in detail by one and two dimensional Nuclear Magnetic Resonance (NMR) spectroscopy and ElectroSpray Ionization Fourier Transform-Ion Cyclotron Resonance (ESI FT-ICR) mass spectrometry.

An efficient method for visualization and growth of fluorescent Xanthomonas oryzae pv. oryzae in planta

PubMed Central

Han, Sang-Wook; Park, Chang-Jin; Lee, Sang-Won; Ronald, Pamela C

2008-01-01

Background Xanthomonas oryzae pv. oryzae, the causal agent of bacterial blight disease, is a serious pathogen of rice. Here we describe a fluorescent marker system to study virulence and pathogenicity of X. oryzae pv. oryzae. Results A fluorescent X. oryzae pv. oryzae Philippine race 6 strain expressing green fluorescent protein (GFP) (PXO99GFP) was generated using the gfp gene under the control of the neomycin promoter in the vector, pPneo-gfp. The PXO99GFPstrain displayed identical virulence and avirulence properties as the wild type control strain, PXO99. Using fluorescent microscopy, bacterial multiplication and colonization were directly observed in rice xylem vessels. Accurate and rapid determination of bacterial growth was assessed using fluoremetry and an Enzyme-Linked ImmunoSorbant Assay (ELISA). Conclusion Our results indicate that the fluorescent marker system is useful for assessing bacterial infection and monitoring bacterial multiplication in planta. PMID:18826644

Of smuts, blasts, mildews, and blights: cAMP signaling in phytopathogenic fungi.

PubMed

Lee, Nancy; D'Souza, Cletus A; Kronstad, James W

2003-01-01

cAMP regulates morphogenesis and virulence in a wide variety of fungi including the plant pathogens. In saprophytic yeasts such as Saccharomyces cerevisiae, cAMP signaling plays an important role in nutrient sensing. In filamentous saprophytes, the cAMP pathway appears to play an integral role in vegetative growth and sporulation, with possible connections to mating. Infection-related morphogenesis includes sporulation (conidia and teliospores), formation of appressoria, infection hyphae, and sclerotia. Here, we review studies of cAMP signaling in a variety of plant fungal pathogens. The primary fungi to be considered include Ustilago maydis, Magnaporthe grisea, Cryphonectria parasitica, Colletotrichum and Fusarium species, and Erisyphe graminis. We also include related information on Trichoderma species that act as mycoparasites and biocontrol agents of phytopathogenic fungi. We point out similarities in infection mechanisms, conservation of signaling components, as well as instances of cross-talk with other signaling pathways.

Effect of Temperature on Growth and Sporulation of US-22, US-23, and US-24 Clonal Lineages of Phytophthora infestans and Implications for Late Blight Epidemiology.

PubMed

Seidl Johnson, Anna C; Frost, Kenneth E; Rouse, Douglas I; Gevens, Amanda J

2015-04-01

Epidemics of late blight, caused by Phytophthora infestans (Mont.) de Bary, have been studied by plant pathologists and regarded with great concern by potato and tomato growers since the Irish potato famine in the 1840s. P. infestans populations have continued to evolve, with unique clonal lineages arising which differ in pathogen fitness and pathogenicity, potentially impacting epidemiology. In 2012 and 2013, the US-23 clonal lineage predominated late blight epidemics in most U.S. potato and tomato production regions, including Wisconsin. This lineage was unknown prior to 2009. For isolates of three recently identified clonal lineages of P. infestans (US-22, US-23, and US-24), sporulation rates were experimentally determined on potato and tomato foliage and the effect of temperature on lesion growth rate on tomato was investigated. The US-22 and US-23 isolates had greater lesion growth rates on tomato than US-24 isolates. Sporulation rates for all isolates were greater on potato than tomato, and the US-23 isolates had greater sporulation rates on both tomato and potato than the US-22 and US-24 isolates. Experimentally determined correlates of fitness were input to the LATEBLIGHT model and epidemics were simulated using archived Wisconsin weather data from four growing seasons (2009 to 2012) to investigate the effect of isolates of these new lineages on late blight epidemiology. The fast lesion growth rates of US-22 and US-23 isolates resulted in severe epidemics in all years tested, particularly in 2011. The greater sporulation rates of P. infestans on potato resulted in simulated epidemics that progressed faster than epidemics simulated for tomato; the high sporulation rates of US-23 isolates resulted in simulated epidemics more severe than simulated epidemics of isolates of the US-22 and US-24 isolates and EC-1 clonal lineages on potato and tomato. Additionally, US-23 isolates consistently caused severe simulated epidemics when lesion growth rate and sporulation were input into the model singly or together. Sporangial size of the US-23 isolates was significantly smaller than that of US-22 and US-24 isolates, which may result in more efficient release of sporangia from the tomato or potato canopy. Our experimentally determined correlates of fitness and the simulated epidemics resulting from their incorporation into the LATEBLIGHT model suggest that US-23 isolates of P. infestans may have the greatest fitness among currently prevalent lineages and may be the most likely lineage to persist in the P. infestans population. The US-23 clonal lineage has been documented as the most prevalent lineage in recent years, indicating its overall fitness. In our work, US-23 had the highest epidemic potential among current genotypes. Given that epidemic potential is a component of fitness, this may, in part, explain the current predominance of the US-23 lineage.