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

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.

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Variation in Pathogenicity and Aggressiveness of Erysiphe necator from Different Vitis spp. and Geographic Origins in the Eastern United States

Phytopathology ◽

10.1094/phyto-01-10-0023 ◽

2010 ◽

Vol 100 (11) ◽

pp. 1185-1193 ◽

Cited By ~ 11

Author(s):

Omer Frenkel ◽

Marin Talbot Brewer ◽

Michael G. Milgroom

Keyword(s):

United States ◽

Powdery Mildew ◽

Lesion Size ◽

Host Specialization ◽

Eastern North America ◽

Eastern United States ◽

Erysiphe Necator ◽

Geographic Origins ◽

Powdery Mildew Pathogen ◽

Vitis Spp

Eastern North America is considered the center of diversity for many Vitis spp. and for the grape powdery mildew pathogen, Erysiphe necator. However, little is known about populations of E. necator from wild Vitis spp. We determined the phenotypic variation in pathogenicity and aggressiveness of E. necator among isolates from wild and domesticated Vitis spp. from diverse geographic regions in the eastern United States. To test pathogenicity, we inoculated 38 E. necator isolates on three wild Vitis spp., two commercially grown hybrids and the European wine grape, Vitis vinifera. V. rotundifolia (muscadine grape) was the only host species on which complete host specialization was evident; it was only susceptible to isolates collected from V. rotundifolia. All isolates, regardless of source host, were pathogenic on the other Vitis spp. We found no differences in components of aggressiveness latent period and lesion size among isolates from different source hosts when inoculated on V. vinifera, which is highly susceptible to powdery mildew. However significant variation was evident among isolates on the more resistant V. labruscana ‘Niagara’. Isolates from the wild species V. aestivalis were the most aggressive, whereas isolates from V. vinifera were not more aggressive than isolates from other source hosts. Greater aggressiveness was also detected among isolates from the southeastern United States compared with isolates from the northeastern United States.

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Adaptive genomic structural variation in the grape powdery mildew pathogen, Erysiphe necator

BMC Genomics ◽

10.1186/1471-2164-15-1081 ◽

2014 ◽

Vol 15 (1) ◽

pp. 1081 ◽

Cited By ~ 65

Author(s):

Laura Jones ◽

Summaira Riaz ◽

Abraham Morales-Cruz ◽

Katherine CH Amrine ◽

Brianna McGuire ◽

...

Keyword(s):

Powdery Mildew ◽

Structural Variation ◽

Erysiphe Necator ◽

Genomic Structural Variation ◽

Powdery Mildew Pathogen ◽

Grape Powdery Mildew

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Differential Gene Expression During Conidiation in the Grape Powdery Mildew Pathogen, Erysiphe necator

Phytopathology ◽

10.1094/phyto-11-10-0295 ◽

2011 ◽

Vol 101 (7) ◽

pp. 839-846 ◽

Cited By ~ 12

Author(s):

Laura Wakefield ◽

David M. Gadoury ◽

Robert C. Seem ◽

Michael G. Milgroom ◽

Qi Sun ◽

...

Keyword(s):

Gene Expression ◽

Powdery Mildew ◽

Differential Gene Expression ◽

Polymorphism Analysis ◽

Erysiphe Necator ◽

Powdery Mildews ◽

Differential Gene ◽

Powdery Mildew Pathogen ◽

Fungal Genes ◽

Grape Powdery Mildew

Asexual sporulation (conidiation) is coordinately regulated in the grape powdery mildew pathogen Erysiphe necator but nothing is known about its genetic regulation. We hypothesized that genes required for conidiation in other fungi would be upregulated at conidiophore initiation or full conidiation (relative to preconidiation vegetative growth and development of mature ascocarps), and that the obligate biotrophic lifestyle of E. necator would necessitate some novel gene regulation. cDNA amplified fragment length polymorphism analysis with 45 selective primer combinations produced ≈1,600 transcript-derived fragments (TDFs), of which 620 (39%) showed differential expression. TDF sequences were annotated using BLAST analysis of GenBank and of a reference transcriptome for E. necator developed by 454-FLX pyrosequencing of a normalized cDNA library. One-fourth of the differentially expressed, annotated sequences had similarity to fungal genes of unknown function. The remaining genes had annotated function in metabolism, signaling, transcription, transport, and protein fate. As expected, a portion of orthologs known in other fungi to be involved in developmental regulation was upregulated immediately prior to or during conidiation; particularly noteworthy were several genes associated with the light-dependent VeA regulatory system, G-protein signaling (Pth11 and a kelch repeat), and nuclear transport (importin-β and Ran). This work represents the first investigation into differential gene expression during morphogenesis in E. necator and identifies candidate genes and hypotheses for characterization in powdery mildews. Our results indicate that, although control of conidiation in powdery mildews may share some basic elements with established systems, there are significant points of divergence as well, perhaps due, in part, to the obligate biotrophic lifestyle of powdery mildews.

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Specific Isolation of RNA from the Grape Powdery Mildew Pathogen Erysiphe necator, an Epiphytic, Obligate Parasite

Journal of Phytopathology ◽

10.1111/j.1439-0434.2009.01578.x ◽

2010 ◽

Vol 158 (1) ◽

pp. 69-71 ◽

Cited By ~ 6

Author(s):

Lance Cadle-Davidson ◽

Laura Wakefield ◽

Robert C. Seem ◽

David M. Gadoury

Keyword(s):

Powdery Mildew ◽

Erysiphe Necator ◽

Obligate Parasite ◽

Powdery Mildew Pathogen ◽

Grape Powdery Mildew

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

Phytopathology ◽

10.1094/phyto-09-10-0237 ◽

2011 ◽

Vol 101 (4) ◽

pp. 502-508 ◽

Cited By ~ 35

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.

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First Report of Powdery Mildew Caused by Podosphaera xanthii (syn. P. fusca) on Cocklebur in Korea

Plant Disease ◽

10.1094/pdis-10-12-0951-pdn ◽

2013 ◽

Vol 97 (6) ◽

pp. 842-842 ◽

Cited By ~ 2

Author(s):

H. B. Lee

Keyword(s):

Powdery Mildew ◽

Natural Infection ◽

Morphological Characteristics ◽

Its Region ◽

Xanthium Strumarium ◽

Podosphaera Xanthii ◽

First Report ◽

Rdna Its ◽

Causal Fungus ◽

Powdery Mildew Pathogen

Cocklebur (Xanthium strumarium L., Asteraceae) is an annual broadleaf weed native to the Americas and eastern Asia. The plant is known as one of the worst competitive weeds in soybean fields and also is known to have some phytopharmacological or toxicological properties. In October 2011, a powdery mildew disease was observed on cocklebur growing in a natural landscape at Geomun Oreum located in Jeju Island, South Korea. Initial signs appeared as thin white colonies, which subsequently developed abundant growth on adaxial leaf surfaces. As the disease progressed, brown discoloration extended down infected leaves which withered. Conidia were formed singly and terminally on conidiophores. Primary conidia (20.3 to 28.6 [average 25.1] μm long × 11.1 to 15.2 [14.3] μm wide, n = 30) were ellipsoid with a round apex and truncate base. Conidiophores were straight or slightly curved and 60.1 to 101.7 (97.3) μm long × 8.2 to 13.2 (11.3) μm wide. Chasmothecia were not observed. No fibrosin bodies were observed in the conidia. Morphological characteristics were consistent with descriptions of Podosphaera xanthii (syn. P. fusca) (2,4). To confirm the identity of the causal fungus, the internal transcribed spacer (ITS) region inclusive of 5.8S and 28S rDNA was amplified from white patches consisting of mycelia and conidia on one leaf using ITS1 (5′-TCCGTAGGTGAACCTGCGG-3′) and LR5F (5′-GCTATCCTGAGGGAAAC-3′), and LROR (5′-ACCCGCTGAACTTAAGC-3′) and LR5F primer sets, respectively. The resulting sequences were deposited in GenBank (Accession Nos. JX502022 and JX964999). A NCBI BLASTn search revealed that the rDNA ITS (JX502022) and 28S (JX964999) homologies of isolate EML-XSPW1 represented 99.6% (512/514) and 100% (803/803) identity values with those of P. xanthii (AB040330 and AB462792, respectively). The rDNA ITS and 28S sequence analysis revealed that the causal fungus clustered with P. xanthii (syn. P. fusca), falling into the Xanthii/Fusca phylogenetic group (2,4). Pathogenicity was confirmed through inoculations made by gently pressing infected leaves onto mature leaves of healthy cocklebur plants in the field in August. The six inoculated leaves were sealed in sterilized vinyl bags to maintain humid conditions for 2 days. Seven days after inoculation, symptoms similar to those observed under natural infection were observed on the inoculated plant leaves. No symptoms developed on the uninoculated control plants. A fungal pathogen that was morphologically identical to the fungus originally observed on diseased plants was also observed on inoculated plants. Erysiphe cichoracearum, E. communis, Oidium asteris-punicei, O. xanthimi, P. xanthii, and P. fuliginea have all been reported to cause powdery mildew on cocklebur (1). P. xanthii was first reported on X. strumarium in Russia (3). To our knowledge, this is the first report of powdery mildew on cocklebur caused by P. xanthii in Korea. The powdery mildew pathogen may represent an option for biocontrol of the noxious weed in the near future. References: (1) D. F. Farr and A. Y. Rossman. Fungal Databases, Systematic Mycology and Microbiology Laboratory, ARS, USDA. Retrieved from http://nt.ars-grin.gov/fungaldatabases , December 11, 2012. (2) H. B. Lee. J. Microbiol. 51:1075, 2012. (3) V. A. Rusanov and T. S. Bulgakov. Mikol. Fitopatol. 42:314, 2008. (4) S. Takamatsu et al. Persoonia 24:38, 2010.

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Identification and utilization of a new Erysiphe necator isolate NAFU1 to quickly evaluate powdery mildew resistance in wild Chinese grapevine species using detached leaves

Plant Physiology and Biochemistry ◽

10.1016/j.plaphy.2015.11.003 ◽

2016 ◽

Vol 98 ◽

pp. 12-24 ◽

Cited By ~ 9

Author(s):

Yu-Rong Gao ◽

Yong-Tao Han ◽

Feng-Li Zhao ◽

Ya-Juan Li ◽

Yuan Cheng ◽

...

Keyword(s):

Powdery Mildew ◽

Powdery Mildew Resistance ◽

Erysiphe Necator ◽

Mildew Resistance ◽

Detached Leaves

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Vitis rupestris B38 Confers Isolate-Specific Quantitative Resistance to Penetration by Erysiphe necator

Phytopathology ◽

10.1094/phyto-09-14-0260-r ◽

2015 ◽

Vol 105 (8) ◽

pp. 1097-1103 ◽

Cited By ~ 12

Author(s):

Paola Barba ◽

Lance Cadle-Davidson ◽

Erin Galarneau ◽

Bruce Reisch

Keyword(s):

Powdery Mildew ◽

Quantitative Resistance ◽

Penetration Resistance ◽

Sources Of Resistance ◽

Erysiphe Necator ◽

Breeding Lines ◽

Vitis Rupestris ◽

Growing Seasons ◽

Detached Leaves ◽

Grape Breeding

Vitis rupestris B38 is a North American grapevine resistant to the major pathogen of cultivated grapevines, Erysiphe necator. Sources of powdery mildew resistance, like V. rotundifolia, are widely used in grape breeding but are already threatened, even before commercialization, by isolates that can reproduce on Run1 and other rotundifolia-derived breeding lines. Thus, complementary sources of resistance are needed to improve resistance durability. The segregation of foliar powdery mildew severity in an F1 family, derived from a cross of V. rupestris B38 × V. vinifera ‘Chardonnay’, was observed in the field over three growing seasons and in potted vines following single-isolate inoculation. A pattern of continuous variation was observed in every instance. Mechanisms of resistance were analyzed on the resistant and susceptible parent by using microscopy to quantify the ability of the pathogen to penetrate and to form a colony on detached leaves. While ‘Chardonnay’ was susceptible in all tested conditions, V. rupestris B38 resistance was characterized by a reduction in pathogen penetration, with an effect of leaf position and significant differences among powdery mildew isolates. Segregation of the ability of the pathogen to penetrate and form a colony in F1 individuals showed a pattern of quantitative penetration resistance with no delay or restriction on colony formation once penetration has been achieved. Moreover, V. rupestris B38 showed an enhanced penetration resistance to a powdery mildew isolate with the ability to overcome the Run1 gene, making it an interesting resistance source to prolong the durability of this gene.

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