scholarly journals A Single Dominant Locus, Ren4, Confers Rapid Non-Race-Specific Resistance to Grapevine Powdery Mildew

2011 ◽  
Vol 101 (4) ◽  
pp. 502-508 ◽  
Author(s):  
David W. Ramming ◽  
Franka Gabler ◽  
Joe Smilanick ◽  
Molly Cadle-Davidson ◽  
Paola Barba ◽  
...  
Keyword(s):  
New York ◽  
Powdery Mildew ◽  
Natural Infection ◽  
Durable Resistance ◽  
Resistance Mechanism ◽  
Segregation Ratio ◽  
Powdery Mildew Fungus ◽  
Grapevine Powdery Mildew ◽  
Highly Correlated ◽  
Resistant Progeny

In the present study we screened the progeny of Vitis vinifera × V. romanetii populations segregating for resistance to powdery mildew and determined the presence of a single, dominant locus, Ren4, conferring rapid and extreme resistance to the grapevine powdery mildew fungus Erysiphe necator. In each of nine Ren4 pseudo-backcross 2 (pBC2) and pBC3 populations (1,030 progeny), resistance fit a 1:1 segregation ratio and overall segregated as 543 resistant progeny to 487 susceptible. In full-sib progeny, microscopic observations revealed the reduction of penetration success rate (as indicated by the emergence of secondary hyphae) from 86% in susceptible progeny to below 10% in resistant progeny. Similarly, extreme differences were seen macroscopically. Ratings for Ren4 pBC2 population 03-3004 screened using natural infection in a California vineyard and greenhouse and using artificial inoculation of an aggressive New York isolate were fully consistent among all three pathogen sources and environments. From 2006 to 2010, Ren4 pBC2 and pBC3 vines were continuously screened in California and New York (in the center of diversity for E. necator), and no sporulating colonies were observed. For population 03-3004, severity ratings on leaves, shoots, berries, and rachises were highly correlated (R2 = 0.875 to 0.996) in the vineyard. Together, these data document a powdery mildew resistance mechanism not previously described in the Vitaceae or elsewhere, in which a dominantly inherited resistance prevents hyphal emergence and is non-race-specific and tissue-independent. In addition to its role in breeding for durable resistance, Ren4 may provide mechanistic insights into the early events that enable powdery mildew infection.

scholarly journals The Ambivalence of the Barley Mlo Locus: Mutations Conferring Resistance Against Powdery Mildew (Blumeria graminis f. sp. hordei) Enhance Susceptibility to the Rice Blast Fungus Magnaporthe grisea

1999 ◽  
Vol 12 (6) ◽  
pp. 508-514 ◽  
Author(s):  
Birgit Jarosch ◽  
Karl-Heinz Kogel ◽  
Ulrich Schaffrath
Keyword(s):  
Powdery Mildew ◽  
Rice Blast ◽  
Magnaporthe Grisea ◽  
Durable Resistance ◽  
Rice Blast Fungus ◽  
Blumeria Graminis ◽  
Negative Regulator ◽  
Powdery Mildew Fungus ◽  
Mesophyll Cells ◽  
Blast Fungus

Recessive alleles of the barley Mlo locus confer non-race-specific resistance against the powdery mildew fungus Blumeria graminis f. sp. hordei (Bgh). Recently the Mlo gene has been isolated and it was suggested that the Mlo product is a negative regulator of cell death. Thus, loss of function can precondition cells to a higher responsiveness for the onset of multiple defense functions. Here, we document an enhanced susceptibility of barley mlo mutants to the rice blast fungus Magnaporthe grisea. The disease phenotype is independent of the barley cultivar in which the mlo allele has been introgressed and occurs in equal amounts in barley backcross lines of cv. Ingrid carrying the mlo-1, mlo-3, or mlo-5 allele. Ror genes, which are required for the full expression of mlo resistance in barley against Bgh, do not affect the specific mlo-mediated phenotype observed after M. grisea infection. Formation of an effective papilla restricts blast development in epidermal cells of Mlo plants. In contrast, papillae are mostly penetrated in mlo mutants and, as a consequence, the fungus spreads into adjacent mesophyll cells. Both wild-type plants and mlo mutants did not differ in perception of a purified elicitor derived from M. grisea. Thus, we hypothesize that a functional Mlo protein is a prerequisite for penetration resistance of barley to fungal pathogens like M. grisea. The benefit of mlo alleles for durable resistance in barley and a proposed role of mlo-type-mutations in rice are discussed.

scholarly journals Variation Within and Among Vitis spp. for Foliar Resistance to the Powdery Mildew Pathogen Erysiphe necator

Plant Disease ◽  
2011 ◽  
Vol 95 (2) ◽  
pp. 202-211 ◽  
Author(s):  
Lance Cadle-Davidson ◽  
David R. Chicoine ◽  
Nancy H. Consolie
Keyword(s):  
Powdery Mildew ◽  
Control Strategies ◽  
Natural Infection ◽  
Durable Resistance ◽  
Erysiphe Necator ◽  
Detached Leaves ◽  
Cold Hardy ◽  
Powdery Mildew Pathogen ◽  
Vitis Spp ◽  
Selection Of

To complement existing control strategies, grape growers desire cultivars with resistance to powdery mildew caused by Erysiphe necator. Numerous disease resistance screens of diverse Vitis germplasm have been conducted previously to identify powdery mildew resistance but ratings of named cultivars were inconsistent and identities of resistant individuals in wild species were not typically provided. In the current study, controlled inoculations of a single isolate were made onto detached leaves from 1,025 Vitis accessions. The results were compared with natural epidemics in two vineyards: the cold-hardy Vitis spp. repository in Geneva, NY, in 2007–08, and a replicated vineyard of 89 Vitis accessions in Fredonia, NY in 2006–08. Of the genotypes screened using both natural infection and single-isolate inoculation, 33% were resistant to a single isolate but susceptible to diverse isolates in either or both vineyards, possibly due to race-specific resistance. This was exemplified by selection of E. necator genotypes virulent to Vitis labrusca in the Fredonia, NY vineyard, which is surrounded by production of the interspecific labrusca hybrids Concord and Niagara. Otherwise, there was good correlation of ratings between the vineyard and single-isolate ratings (r = 0.55 to 0.56) and between Geneva and Fredonia vineyard ratings (r = 0.75). No accession rated in all three screens was immune from infection. Although individual accessions of V. aestivalis, V. palmata, Vitis × doaniana, and Ampelopsis brevipedunculata were resistant in Geneva and Fredonia, each well-represented species had notable intraspecific variation in resistance. For 129 interspecific hybrids in this and previous studies, ratings infrequently corresponded among previous studies (39%) and between the current and previous studies (17 to 46%). However, three cultivars (Cayuga White, Diana, and Mars) were consistently rated as resistant across four independent studies. The results underscore the importance of uniform testing in multiple environments and the need for strategies for the development of cultivars with durable resistance.

Development of an Advisory System for Grapevine Powdery Mildew in Eastern North America: A Reassessment of Epidemic Progress

2010 ◽  
Vol 11 (1) ◽  
pp. 35
Author(s):  
Michelle M. Moyer ◽  
David M. Gadoury ◽  
Peter A. Magarey ◽  
Wayne F. Wilcox ◽  
Robert C. Seem
Keyword(s):  
New York ◽  
Powdery Mildew ◽  
Historical Data ◽  
Colony Growth ◽  
Optimal Range ◽  
Annual Variations ◽  
Advisory System ◽  
Grapevine Powdery Mildew ◽  
Eastern Usa ◽  
Epidermal Necrosis

Historical data indicated that year-to-year variation in severity of powdery mildew fruit infection in New York was not directly related to annual variations in temperature or relative humidity through their known effects upon conidial germination, colony expansion, or latent period. Although severity of fruit infection varied from 0.02 to 61% among years, these environmental factors generally remained in the optimal range for the pathogen, with only slight year-to-year variations during the brief period that fruit were susceptible to infection. Vineyard experiments in New York and Australia indicated that colony growth was slower and sparser than would be expected from previous lab studies. Additional experiments indicated that transient exposure to temperatures near 4°C for a few hours had a debilitating effect on mildew colonies and produced growth similar to that observed on ontogenically-resistant tissues: slow and sparse with epidermal necrosis. Additional studies on seasonal release of ascospores from overwintering cleistothecia indicated that a large proportion of inoculum was often released prior to local grapevine budbreak at multiple sites in the eastern USA. These findings may represent key elements in forecasting potential severity of fruit infection in cool climates such as New York. Accepted for publication 28 January 2010. Published 26 May 2010.

scholarly journals Large-Scale Data Integration Reveals Colocalization of Gene Functional Groups with Meta-QTL for Multiple Disease Resistance in Barley

2011 ◽  
Vol 24 (12) ◽  
pp. 1492-1501 ◽  
Author(s):  
Patrick Schweizer ◽  
Nils Stein
Keyword(s):  
Disease Resistance ◽  
Powdery Mildew ◽  
Data Integration ◽  
Functional Groups ◽  
Crop Production ◽  
Large Scale ◽  
Durable Resistance ◽  
Added Value ◽  
Powdery Mildew Fungus ◽  
Polygenic Inheritance

Race-nonspecific and durable resistance of plant genotypes to major pathogens is highly relevant for yield stability and sustainable crop production but difficult to handle in practice due to its polygenic inheritance by quantitative trait loci (QTL). As far as the underlying genes are concerned, very little is currently known in the most important crop plants such as the cereals. Here, we integrated publicly available data for barley (Hordeum vulgare subsp. vulgare) in order to detect the most important genomic regions for QTL-mediated resistance to a number of fungal pathogens and localize specific functional groups of genes within these regions. This identified 20 meta-QTL, including eight hot spots for resistance to multiple diseases that were distributed over all chromosomes. At least one meta-QTL region for resistance to the powdery mildew fungus Blumeria graminis was found to be co-linear between barley and wheat, suggesting partial evolutionary conservation. Large-scale genetic mapping revealed that functional groups of barley genes involved in secretory processes and cell-wall reinforcement were significantly over-represented within QTL for resistance to powdery mildew. Overall, the results demonstrate added value resulting from large-scale genetic and genomic data integration and may inform genomic-selection procedures for race-nonspecific and durable disease resistance in barley.

scholarly journals Genetic Mapping and Nucleotide Diversity of Two Powdery Mildew Resistance Loci in Melon (Cucumis melo)

2020 ◽  
Vol 110 (12) ◽  
pp. 1970-1979
Author(s):  
Cui Haonan ◽  
Ding Zhuo ◽  
Fan Chao ◽  
Zhu Zicheng ◽  
Zhang Hao ◽  
...  
Keyword(s):  
Powdery Mildew ◽  
Cucumis Melo ◽  
Nucleotide Diversity ◽  
Bulked Segregant Analysis ◽  
Durable Resistance ◽  
Recessive Gene ◽  
Segregation Ratio ◽  
Epistatic Effect ◽  
Fixation Index ◽  
Mendelian Segregation

Powdery mildew (PM) significantly and negatively affects the yield and quality of melon (Cucumis melo) worldwide. Race 2F is the predominant physiological race of the pathogen Podosphaera xanthii in many regions. We used accessions PMR 6 (P1; resistant to PM) and M1-7 (P2; susceptible to PM) to analyze the inheritance of resistance to PM (race 2F). The ratio between resistant and susceptible individuals fits a Mendelian segregation ratio of 13:3 in a total of 256 F2 individuals and 1:1 in BC1P2. The resistance to PM in PMR 6 was governed by two genes: a dominant (AA) gene with an epistatic effect and a recessive gene (bb). Only individuals with aaBB or aaBb genotypes were susceptible to PM. Two PM resistance loci, Pm2.1 and pm12.1, were mapped on chromosomes 2 and 12 by bulked segregant analysis and secondary mapping by quantitative trait loci analysis with 18 markers. A new marker-assisted selection system to identify melon genotypes resistant or susceptible to PM was developed and tested in 93 melon accessions. Nucleotide diversity (π) and fixation index (Fst) for the two PM resistance loci were estimated using resequencing data of 336 melons from three groups: C. melo subsp. agrestis, Cucumis melo subsp. melo, and the intermediate type. The lowest π was observed in C. melo ssp. agrestis, and the highest Fst value was between C. melo ssp. agrestis and C. melo ssp. melo. The findings provide a promising tool that can be used to accelerate breeding for durable resistance to PM.

scholarly journals First Report of Powdery Mildew of Tomato Caused by an Erysiphe sp. in Connecticut

Plant Disease ◽  
1997 ◽  
Vol 81 (2) ◽  
pp. 229-229 ◽  
Author(s):  
V. L. Smith ◽  
S. M. Douglas ◽  
J. A. LaMondia
Keyword(s):  
New York ◽  
Powdery Mildew ◽  
Powdery Mildew Fungus ◽  
First Report ◽  
Eastern Black Nightshade ◽  
Tomato Seedlings ◽  
Nicotiana Tabacum L ◽  
Leaf Surfaces ◽  
Greenhouse Tomatoes ◽  
Solanaceous Plants

In 1995 and 1996, powdery mildew was observed on several samples of field-grown tomato foliage (Lycopersicon esculentum Mill.; various cultivars) submitted to the CAES Plant Disease and Information Office. Symptoms included gray superficial mycelium with abundant sporulation on adaxial and abaxial leaf surfaces, followed in the field by dessication of the foliage and rapid defoliation. No cleistothecia were observed, and single-celled, hyaline, ellipsoidal conidia occurred, usually singly, on unbranched conidiophores. Pyriform conidia occurred at a frequency of less than 1%. Conidia ranged in length from 25.6 to 43.2 μm (mean = 33.6, SE = 0.4) and in width from 13.1 to 23.1 μm (mean = 18.2, SE = 0.2; n = 500). Fibrosin bodies were not observed, and vacuoles were present. Based on conidial characteristics, the fungus was identified as an unknown Erysiphe sp. To confirm pathogenicity, 2-week-old tomato seedlings (cv. Rutgers) were inoculated by shaking dry conidia onto the leaves and placed within plastic tents on a greenhouse bench. Control plants were treated identically but not inoculated. The inoculated plants developed foliar powdery mildew symptoms, and sporulation was observed. Susceptible cultivars that were naturally infected included Better Boy, Better Beef, Celebrity, Rutgers, Ultra Magnum, Ultra Sweet, Whopper, Yellow Brandywine; cherry type tomatoes Matts Wild Cherry and Sweet Chelsea; and plum type tomatoes Roma and Super San Marzano. Eastern black nightshade (Solanum ptycanthum Dunal), eggplant (S. melongena L. ‘Black Pride’), and tobacco (Nicotiana tabacum L. ‘C9’) were also naturally infected under greenhouse conditions. However, conidia size and number of conidia per conidiophore differed between hosts. Conidia from tobacco, eggplant, and nightshade averaged 37.8 × 19.1 μm (SE = 0.5 and 0.2, respectively) with a 95% CI of 35.5 to 40.0 × 18.1 to 20.3 μm (n = 300). Conidia from tomato were smaller, averaging 33.6 × 18.2 μm (SE = 0.3 and 0.2, respectively) with a 95% CI of 32.7 to 34.4 × 17.5 to 18.9 μm (n = 300). Factorial inoculation experiments between tomato and other hosts demonstrated cross-infectivity, but isolates originally from tobacco had significantly larger conidia when infecting tomato than isolates originally from tomato infecting tobacco. Powdery mildew isolates on tomato had fewer (P = 0.001) conidia per conidiophore (mean = 1.39, range = 1 to 4) than isolates infecting tobacco inoculated at the same time and held under the same conditions (mean = 2.54, range = 1 to 6). These results demonstrate considerable morphological variation in the powdery mildew fungus, perhaps associated with hosts such as tomato or other solanaceous plants. This is the first report of powdery mildew of tomato and tobacco in Connecticut. Powdery mildew of tomato has been reported to occur in the field in California, and in greenhouse tomatoes in New York (2). Powdery mildew of tobacco has only been reported on artificially inoculated plants in California (1). References: (1) C. R. Arredondo et al. Plant Dis. 80:1303, 1996. (2) D. M. Karasevicz and T. A. Zitter. Plant Dis. 80:709, 1996.

Symptoms Development as Tools to Differentiate Dorizontal Resistance in Sunflower

Agrotek ◽  
2018 ◽  
Vol 2 (6) ◽  
Author(s):  
Cipta Meliala ◽  
Felicity Fear ◽  
Denis Tourvieille de Labrouhe
Keyword(s):  
Downy Mildew ◽  
Natural Infection ◽  
Resistance Mechanism ◽  
Good Method ◽  
Vegetative Stage ◽  
Horizontal Resistance ◽  
Symptom Development ◽  
Plasmopara Halstedii ◽  
Controlled Conditions ◽  
Symptom Progression

Downy mildew symptoms caused by Plasmopara halstedii encountered in sunflower plantation are varied. This variation may be related to the resistance mechanism presented by plant to the invasion of the fungus. Our objectives were firstly is to evaluate symptom development after fungus race 710 inoculation on some vegetative stage of susceptible hybrid. Second objective is to evaluate the reaction some sunflower genotypes after fungus inoculation. The study was conducted under controlled conditions or under netting cages in the field. The development of downy mildew symptoms were affected by all factors studied. Shoot inoculation may present a good method to produce downy mildew symptom similar to the natural infection. Downy mildew symptom progression may be used to screen a genotype with a horizontal resistance.

Relationship between Coffee Prices in Spot and Futures Markets-An Empirical Analysis

2020 ◽  
pp. 180-188
Keyword(s):  
New York ◽  
Correlation Coefficients ◽  
Strong Relationship ◽  
Futures Market ◽  
Regression Coefficients ◽  
Futures Prices ◽  
Market Prices ◽  
Spot Prices ◽  
Correlation And Regression Analysis ◽  
Highly Correlated

The present study explored the relationship between spot and futures coffee prices. The Correlation and Regression analysis were carried out based on monthly observations of International Coffee Organization (ICO) indicator prices of the four groups (Colombian Milds, Other Milds, Brazilian Naturals, and Robustas) representing Spot markets and the averages of 2nd and 3rd positions of the Intercontinental Exchange (ICE) New York for Arabica and ICE Europe for Robusta representing the Futures market for the period 1990 to 2019. The study also used the monthly average prices paid to coffee growers in India from 1990 to 2019. The estimated correlation coefficients indicated both the Futures prices and Spot prices of coffee are highly correlated. Further, estimated regression coefficients revealed a very strong relationship between Futures prices and Spot prices for all four ICO group indicator prices. Hence, the ICE New York (Arabica) and ICE Europe (Robusta) coffee futures prices are very closely related to Spot prices. The estimated regression coefficients between Futures prices and the price paid to coffee growers in India confirmed the positive relationship, but the dispersion of more prices over the trend line indicates a lesser degree of correlation between the price paid to growers at India and Futures market prices during the study period.

scholarly journals Disruption of barley immunity to powdery mildew by an in-frame Lys-Leu deletion in the essential protein SGT1

Genetics ◽  
2020 ◽  
Vol 217 (2) ◽  
Author(s):  
Antony V E Chapman ◽  
Matthew Hunt ◽  
Priyanka Surana ◽  
Valeria Velásquez-Zapata ◽  
Weihui Xu ◽  
...  
Keyword(s):  
Powdery Mildew ◽  
Fungal Pathogens ◽  
Novel Mutation ◽  
Exome Capture ◽  
Resistance Locus ◽  
Hordeum Vulgare L ◽  
Powdery Mildew Fungus ◽  
Pathogen Effectors ◽  
Cell Processes ◽  
Disease Resistances

Abstract Barley (Hordeum vulgare L.) Mla (Mildew resistance locus a) and its nucleotide-binding, leucine-rich-repeat receptor (NLR) orthologs protect many cereal crops from diseases caused by fungal pathogens. However, large segments of the Mla pathway and its mechanisms remain unknown. To further characterize the molecular interactions required for NLR-based immunity, we used fast-neutron mutagenesis to screen for plants compromised in MLA-mediated response to the powdery mildew fungus, Blumeria graminis f. sp. hordei. One variant, m11526, contained a novel mutation, designated rar3 (required for Mla6 resistance3), that abolishes race-specific resistance conditioned by the Mla6, Mla7, and Mla12 alleles, but does not compromise immunity mediated by Mla1, Mla9, Mla10, and Mla13. This is analogous to, but unique from, the differential requirement of Mla alleles for the co-chaperone Rar1 (required for Mla12 resistance1). We used bulked-segregant-exome capture and fine mapping to delineate the causal mutation to an in-frame Lys-Leu deletion within the SGS domain of SGT1 (Suppressor of G-two allele of Skp1, Sgt1ΔKL308–309), the structural region that interacts with MLA proteins. In nature, mutations to Sgt1 usually cause lethal phenotypes, but here we pinpoint a unique modification that delineates its requirement for some disease resistances, while unaffecting others as well as normal cell processes. Moreover, the data indicate that the requirement of SGT1 for resistance signaling by NLRs can be delimited to single sites on the protein. Further study could distinguish the regions by which pathogen effectors and host proteins interact with SGT1, facilitating precise editing of effector incompatible variants.

Biological relationship of cucumis virus-3 and powdery mildew fungus in bottle gourd

1978 ◽  
Vol 34 (3) ◽  
pp. 336-337 ◽  
Author(s):  
M. A. Qureshi ◽  
C. D. Mayee
Keyword(s):  
Powdery Mildew ◽  
Bottle Gourd ◽  
Powdery Mildew Fungus ◽  
Biological Relationship ◽  
Relationship Of
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