Fungicide Sensitivity Survey of Plasmopara viticola Populations in Georgia Vineyards

Grapevine downy mildew, caused by Plasmopara viticola, is among the most damaging diseases of grapes globally and in the viticultural regions of Georgia (U.S.A.). Although management of this disease typically involves fungicide applications, resistance development in P. viticola can render chemical management ineffective. The objective of this study was to survey fungicide sensitivities of P. viticola populations in vineyards across three regions in Georgia. Samples were collected from eight vineyards in 2017 and four in 2018 and tested phenotypically for sensitivity to quinone outside inhibitor (QoI), carboxylic acid amide (CAA), and phenylamide (PA) fungicides using leaf disc bioassays. In addition, DNA was extracted from P. viticola samples collected from 2015 through 2018 in these 12 vineyards and six others for a total of 18 vineyards sampled. All available DNA samples were tested for the presence of the known resistance-causing mutations G143A (QoI) and G1105S (CAA) using polymerase chain reaction (PCR). This study documented widespread occurrence of QoI resistance in P. viticola in Georgia, with 83.0% of isolates collected in 2017 and 2018 testing positive for QoI resistance based on bioassay and 82.9% of isolates collected from 2015 to 2018 testing positive for QoI resistance through PCR testing. In total, 94.4% (17/18) of surveyed vineyards had confirmed QoI resistance by the conclusion of the survey period. No reduced sensitivity to CAA or PA fungicides was identified. Due to widespread QoI resistance, these fungicides should not be relied upon for downy mildew management in Georgia vineyards with a long history of their use.

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Effect of Detergent on the Quantification of Grapevine Downy Mildew Sporangia from Leaf Discs

HortScience ◽

10.21273/hortsci.50.5.656 ◽

2015 ◽

Vol 50 (5) ◽

pp. 656-660 ◽

Cited By ~ 11

Author(s):

Atsushi Kono ◽

Akihiko Sato ◽

Bruce Reisch ◽

Lance Cadle-Davidson

Keyword(s):

Downy Mildew ◽

Leaf Disc ◽

Plasmopara Viticola ◽

Inhibitory Effect ◽

Tween 20 ◽

Infected Leaf ◽

Grapevine Downy Mildew ◽

Visual Rating ◽

Leaf Discs ◽

Highly Correlated

Grapevine downy mildew (DM), caused by the oomycete Plasmopara viticola (Berk. & Curt.) Berlese & de Toni, is a major disease, especially in humid viticultural areas. Development of resistant cultivars is an important objective for grapevine breeding. To establish a reliable and inexpensive quantitative method to aid in breeding for DM resistance, we improved the method for counting the number of sporangia on leaf discs, and developed a method for counting the number of sporangia in solution. To prevent the loss of DM sporangia from adhesion onto plastic ware, we found as little as 0.01% Tween 20 was effective. On the other hand, this detergent was shown to have a severe inhibitory effect upon DM infection of leaves. We developed a sporangia counting method using dried droplets of DM suspensions, and the method was highly correlated with counting by hemacytometer (R2 > 0.96). The nonparametric Spearman’s rank correlations between visual rating and the number of the sporangia were as high as ρ = 0.82 to 0.91, suggesting that evaluation by the visual rating could provide a good estimate of the sporangia numbers on leaf discs. We established a high-throughput and inexpensive method with acceptable accuracy for DM resistance evaluation based on a leaf disc assay, and our results suggested that visual ratings of infected leaf discs provide a good estimate of sporangia numbers.

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First Report of Carboxylic Acid Amide Fungicide Resistance in Plasmopara viticola (Grapevine Downy Mildew) in North America

Plant Health Progress ◽

10.1094/php-01-18-0005-br ◽

2018 ◽

Vol 19 (2) ◽

pp. 139-139 ◽

Cited By ~ 1

Author(s):

Xuewen Feng ◽

Anton Baudoin

Keyword(s):

North Carolina ◽

Carboxylic Acid ◽

North America ◽

Downy Mildew ◽

Acid Amide ◽

Plasmopara Viticola ◽

Carboxylic Acid Amide ◽

Grapevine Downy Mildew ◽

Grape Downy Mildew ◽

Caa Fungicides

This report documents the first known occurrence in North America of resistance in grape downy mildew (Plasmopara viticola) to the carboxylic acid amide (CAA) fungicides mandipropamid and dimethomorph. These fungicides (FRAC group 40) have been an important component of downy mildew management programs for the past decade. Resistant isolates were obtained at three locations in Virginia and one in North Carolina, at considerable distances from each other. Resistance was documented by bioassay and the presence of the G1105S mutation, which has been associated with CAA resistance of P. viticola in other areas. Further survey is needed to determine the geographic extent of this resistance.

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Europe as a bridgehead in the worldwide invasion history of grapevine downy mildew, Plasmopara viticola

Current Biology ◽

10.1016/j.cub.2021.03.009 ◽

2021 ◽

Author(s):

Michael C. Fontaine ◽

Frédéric Labbé ◽

Yann Dussert ◽

Laurent Delière ◽

Sylvie Richart-Cervera ◽

...

Keyword(s):

Downy Mildew ◽

Plasmopara Viticola ◽

Invasion History ◽

Grapevine Downy Mildew ◽

History Of

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Monitoring of a Single Point Mutation in the PvCesA3 Allele Conferring Resistance to Carboxylic Acid Amide Fungicides in Plasmopara viticola Populations In Yamanashi Prefecture, Japan

Plant Health Progress ◽

10.1094/php-rs-14-0041 ◽

2015 ◽

Vol 16 (2) ◽

pp. 84-87 ◽

Cited By ~ 3

Author(s):

Yoshinao Aoki ◽

Yumi Kawagoe ◽

Nozomi Fujimori ◽

Sayumi Tanaka ◽

Shunji Suzuki

Keyword(s):

Carboxylic Acid ◽

Point Mutation ◽

Fungicide Resistance ◽

Single Point ◽

Acid Amide ◽

Plasmopara Viticola ◽

Single Point Mutation ◽

Carboxylic Acid Amide ◽

Grapevine Downy Mildew ◽

Quinone Outside Inhibitor

The use of the carboxylic acid amide (CAA) fungicide mandipropamid to manage grapevine downy mildew in vineyards in Japan has been increasing since 2010, because of widespread quinone outside inhibitor fungicide resistance in the Plasmopara viticola population. However, CAA fungicide resistance in P. viticola is becoming a serious problem worldwide. In 2013, we monitored for the presence of a single point mutation at codon 1105 of the cellulose synthase gene PvCesA3, which confers resistance to mandipropamid in P. viticola samples collected from four vineyards in Yamanashi prefecture in Japan. Five out of 157 samples were found to be heterozygotes, carrying both the mutated and nonmutated PvCesA3 alleles. Although CAA fungicide-resistant P. viticola isolates have not been reported yet in Japan, the emergence of heterozygous P. viticola populations indicates the potential risk of emergence of resistant homozygotes. Accepted for publication 14 March 2015. Published 1 May 2015

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Downy Mildew from Lake Erie Vineyards is Diverse for the G143A SNP Conferring Resistance to Quinone Outside Inhibitor Fungicides

Plant Health Progress ◽

10.1094/php-2013-0422-01-rs ◽

2013 ◽

Vol 14 (1) ◽

pp. 23

Author(s):

Christopher T. Gee ◽

Stephanie Chestnut ◽

Eilene Duberow ◽

Andrea Collins ◽

Michael A. Shields

Keyword(s):

Downy Mildew ◽

Fungal Pathogens ◽

Lake Erie ◽

Single Mode ◽

Plasmopara Viticola ◽

Qoi Fungicides ◽

Quinone Outside Inhibitor ◽

Development Of Resistance ◽

Qualitative Level ◽

Qoi Resistance

Downy mildew (Plasmopara viticola) is a significant problem in grape vineyards throughout the growing season. Control of downy mildew is carried out with a combination of host tolerance and chemical applications. Even in vineyards planted with very tolerant varieties (e.g., Concord), control is important in years with ideal pathogen conditions. Fungicides with a single mode of action possess a very high potential for the development of resistance. Resistance has been observed often in the Quinone outside inhibitor (QoI) fungicides, such as strobilurins. We ascertained the levels of QoI resistance in downy mildew colonies on diseased leaves using CAPS-PCR to detect the glycine to alanine mutation (G143A) known to confer a qualitative level of resistance in fungal pathogens. Our data uncovered a small percentage of samples that contain G143A, suggesting an overall low level of QoI resistance. The low prevalence of the resistant single nucleotide polymorphism (SNP) suggests that QoI fungicides should remain a viable control mechanism in Lake Erie vineyards. Additionally, it appears that a viticultural region where tolerant hosts predominant and QoI use is minimal, resistance buildup in the pathogen population will be minimal. Accepted for publication 15 January 2013. Published 22 April 2013.

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Analysis of the virome associated to grapevine downy mildew lesions reveals new mycovirus lineages

Virus Evolution ◽

10.1093/ve/veaa058 ◽

2020 ◽

Vol 6 (2) ◽

Cited By ~ 3

Author(s):

M Chiapello ◽

J Rodríguez-Romero ◽

M A Ayllón ◽

M Turina

Keyword(s):

Downy Mildew ◽

High Throughput Sequencing ◽

Rna Viruses ◽

Plasmopara Viticola ◽

Catalytic Triad ◽

Positive Strand ◽

Grapevine Downy Mildew ◽

History Of ◽

Evolutionary Trajectories ◽

Positive Strand Rna

Abstract The obligatory biotrophic oomycetes Plasmopara viticola is the causal agent of downy mildew, a destructive disease of grapevine worldwide. So far, chemical fungicides are widely employed to limit this pathogen, but their adverse effects are stimulating the quest for environmentally friendly alternative approaches. Here, we report on the search for mycoviruses that might be later developed as biocontrol agents for this pathogen. Symptomatic leaves were collected from various regions in Spain and Italy and mycelia associated to leaf lesions was harvested. Total RNA extractions were depleted of rRNA and metatranscriptomes were generated using a high-throughput sequencing approach. The virome associated to leaf lesions was then characterized through a bioinformatic pipeline relying on blast searches against current viral databases. Here, we present an inventory of 283 new RNA viruses: 222 positive strand RNA viruses, 29 negative strand RNA viruses, 27 double-stranded RNA viruses and 5 ORFan virus RdRP segments, which could not be reliably assigned to any existing group in the Riboviria. In addition to ORFan viruses, we found other surprising new evolutionary trajectories in this wide inventory of viruses. The most represented viruses in our collection are those in phylum Lenarviricota, and, among them, a group of mycovirus segments distantly related to narnaviruses, but characterized by a polymerase palm domain lacking subdomain C, with the putative GDD catalytic triad. We also provided evidence of a strict association between two RNA segments that form a new mycovirus clade of positive strand RNA in the phylum Kitrinoviricota, order Martellivirales. In the phylum Negarnaviricota, we report for the first time in the order Mononegavirales a clade of viruses that is ambisense, a feature that so far was present only in the order Bunyavirales. Furthermore, in the same phylum we detected the widespread occurrence and abundant accumulation in our libraries of a distinct mycovirus clade distantly related to the Muvirales and Goujanvirales orders, which so far include only viruses infecting invertebrates. Possible new oomycetes-specific virus clades are also described in the phylum Duplornaviricota. These data greatly expand the evolutionary history of mycoviruses adding new layers of diversity to the realm Riboviria.

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A High-Quality Grapevine Downy Mildew Genome Assembly Reveals Rapidly Evolving and Lineage-Specific Putative Host Adaptation Genes

Genome Biology and Evolution ◽

10.1093/gbe/evz048 ◽

2019 ◽

Vol 11 (3) ◽

pp. 954-969 ◽

Cited By ~ 12

Author(s):

Yann Dussert ◽

Isabelle D Mazet ◽

Carole Couture ◽

Jérôme Gouzy ◽

Marie-Christine Piron ◽

...

Keyword(s):

Downy Mildew ◽

Genome Assembly ◽

Population Genomics ◽

Plasmopara Viticola ◽

Plant Diseases ◽

Host Specialization ◽

Grapevine Downy Mildew ◽

Downy Mildews ◽

Genes Encoding ◽

High Level

Abstract Downy mildews are obligate biotrophic oomycete pathogens that cause devastating plant diseases on economically important crops. Plasmopara viticola is the causal agent of grapevine downy mildew, a major disease in vineyards worldwide. We sequenced the genome of Pl. viticola with PacBio long reads and obtained a new 92.94 Mb assembly with high contiguity (359 scaffolds for a N50 of 706.5 kb) due to a better resolution of repeat regions. This assembly presented a high level of gene completeness, recovering 1,592 genes encoding secreted proteins involved in plant–pathogen interactions. Plasmopara viticola had a two-speed genome architecture, with secreted protein-encoding genes preferentially located in gene-sparse, repeat-rich regions and evolving rapidly, as indicated by pairwise dN/dS values. We also used short reads to assemble the genome of Plasmopara muralis, a closely related species infecting grape ivy (Parthenocissus tricuspidata). The lineage-specific proteins identified by comparative genomics analysis included a large proportion of RxLR cytoplasmic effectors and, more generally, genes with high dN/dS values. We identified 270 candidate genes under positive selection, including several genes encoding transporters and components of the RNA machinery potentially involved in host specialization. Finally, the Pl. viticola genome assembly generated here will allow the development of robust population genomics approaches for investigating the mechanisms involved in adaptation to biotic and abiotic selective pressures in this species.

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Factors affecting zoospore responses towards stomata in hop downy mildew (Pseudoperonospora humuli) including some comparisons with grapevine downy mildew (Plasmopara viticola)

Physiological Plant Pathology ◽

10.1016/0048-4059(73)90013-1 ◽

1973 ◽

Vol 3 (3) ◽

pp. 405-417 ◽

Cited By ~ 31

Author(s):

D.J. Royle ◽

G.G. Thomas

Keyword(s):

Downy Mildew ◽

Plasmopara Viticola ◽

Factors Affecting ◽

Grapevine Downy Mildew ◽

Pseudoperonospora Humuli

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Isolation of Plasmopara viticola from Grapevine Leaves

Proceedings ◽

10.3390/proceedings2019029034 ◽

2019 ◽

Vol 29 (1) ◽

pp. 34

Author(s):

Camelia Ungureanu ◽

Liliana Cristina Soare ◽

Diana Vizitiu ◽

Mirela Calinescu ◽

Irina Fierascu ◽

...

Keyword(s):

Downy Mildew ◽

Plasmopara Viticola ◽

Grapevine Downy Mildew ◽

Grapevine Leaves ◽

Downy Mildew Disease

In order to test some biofungicides, the isolation of Plasmopara viticola was carried out.Plasmopara viticola is a fungus that causes the grapevine downy mildew disease [...]

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