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# A key to sustainable management of the grapevine downy mildew pathogen

François Delmotte

► To cite this version:

François Delmotte. A key to sustainable management of the grapevine downy mildew pathogen. 17th Congress of the Mediterranean Phytopathological Union, Mediterranean Phytopathological Union, Jul 2025, Bari, Italy. pp.301-457, 10.36253/phyto-16678. hal-05304538

HAL Id: hal-05304538

https://hal.inrae.fr/hal-05304538v1

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# A key to sustainable management of the grapevine downy mildew pathogen

François Delmotte

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RÉPUBLIQUE
FRANÇAISE

Liberté
Egalité
Fraternité

INRAO
*Plasmopara viticola, the grapevine downy mildew pathogen*

- Major grapevine disease

- Oomycetes, biotrophic, diploid

- Mixed reproduction system, heterothallic

- Originating from north-eastern America

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## Wild american Vitis

a. *Parthenocissus quinquefolia*

b. *Parthenocissus tricuspidata*

c. *V. cinerea*

d. *V. vulpina*

e. *V. riparia*

f. *V. aestivalis*

## Cultivated Vitis

g. *V. vinifera*

h. *V. labruscana* (concord, niagara)

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Rouxel et al. 2013, New Phytol, 10.1111/nph.12016
Rouxel et al. 2014, Phyopathology, doi.org/10.1094/PHYTO-08-13-0225-R =\> P. viticola clades
Salgado-Salazar C, Thines M. Mycological Progress. 2022 Jul;21(7):63. =\> new Plasmopara species names (blue)
Europe as a bridgehead
in the worldwide invasion history
of grapevine downy mildew, *Plasmopara viticola*

Michael C. Fontaine,¹,²,³,⁴,⁵,⁶,⁷,†* Frédéric Labbe,¹,⁸,⁹ Yann Dussert,¹,⁵,⁶,⁷,⁸,†* Laurent Deléère,⁹,†* Sylvie Richert-Cervera,¹,⁵

Tatiana Giraud,¹,⁵,⁶,⁷,†* and François Delémotte¹,⁵

¹Groningen Institute for Evolutionary Life Sciences (GEIFES), University of Groningen, P.O. Box 11102 CC, Groningen, the Netherlands
²Ecologie Systémique et Evolution, UMI 8075, Université Paris-Saclay, CNRS, Agro-FranceTech, Ouest 91405, France

³Laboratoire MIVEGEC (Université de Montpellier, CNRS 5290, I.RD 229) et Centre de Recherche en Ecologie et Evolution de la Santé (CREEES), Institut de Recherche pour la Développement (IRD), 34394 Montpellier, France

⁴SAVE, INRAE, Bordeaux Sciences Agro, Université de Bordeaux, 33140 Villeneuve d'Ornon, France

†These authors contributed equally

¹Present address: Department of Ecology and Evolution, University of Chicago, Chicago, IL, USA

²Present address: School of Biological and Chemical Sciences, Queen Mary University of London, London, UK

†Twitter: BMAoFontaine

‡Twitter: @GenEvo

¹Lead contact

²Correspondence: michaelFontaine@cnrs.fr (M.C.F.), francois.delémotte@inrae.fr (F.D.)

https://doi.org/10.1016/j.cub.2021.03.009

SUMMARY

Europe is the historical cradle of viticulture, but grapevines (Vitis vinifera) have been increasingly threatened by pathogens and climate change. The invasive oomycete *Plasmopara viticola* causes downy mildew, one of the most devastating grapevine diseases worldwide. Despite major economic consequences, its invasion history remains poorly understood. We analyzed a comprehensive dataset of ~2,000 samples, collected from the most important wine-producing countries, using nuclear and mitochondrial gene sequences and microsatellite markers. Population genetic analyses revealed very low genetic diversity in invasive downy mildew populations worldwide and little evidence of admixture. All the invasive populations originated from only one of the five native North American lineages, the one paralyzing wild summer grape (V. aestivalis). An approximate Bayesian computation-random forest approach allowed inferring the worldwide invasion scenario of *P. viticola*. After an initial introduction into Europe, invasive European populations served as a secondary source of introduction into vineyards worldwide, including China, South Africa, and twice independently, Australia. Only the invasion of Argentina probably represents a tertiary introduction, from Australia. Our findings provide a striking example of a global pathogen invasion resulting from secondary dispersal of a successful invasive population. Our study will also help designing quarantine regulations and efficient breeding for resistance against grapevine downy mildew.

INTRODUCTION

Global changes (e.g., climate warming and international ex-
changes) are favoring increases in the numbers of emerging
diseases caused by invasive pathogens on crops worldwide,
including plant and animal diseases, such as, for example,
the costs of new races of the stem rust fungus in Eastern Africa;*
and Europe*; and of the fungin causing wheat blast disease in
Bangladesh,* both threatening wheat production and becoming
invasive. Most emerging diseases result from biological in-
sions bringing the native host-parasite association back-together
after crop introduction into new areas, or host shifts following
pathogen introductions.¹ An understanding of the evolutionary
processes responsible for emerging crop diseases is important

for preventing further devastating biological invasions and for
controlling introduced populations. This requires elucidation
of the invasion mechanisms, pathways, and demographic pro-
cesses occurring during pathogen invasions (e.g., bottlenecks
and hybridization). Important questions include whether path-
ogen invasions result from host shifts, whether limited genetic
variation has been introduced, whether multiple introductions
and admixture are required for successful invasions, and
whether the invaded areas are colonized directly from native
populations or whether an initial successful invasive population
serves as the source for secondary introductions.

Grapevine (Vitis vinifera subsp. sativa L.) is one striking case of crop threatened by invasive pests. This emblematic crop has a prominent place in the history of European civilization. Grapevine domestication started 8,000 years ago from

A

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Fontaine et al. 2013, Mol Ecol

MOLECULAR ECOLOGY

Molecular Ecology (2013)

doi: 10.1111/mer.12283

Genetic signature of a range expansion and leap-frog
event after the recent invasion of Europe by the
grapevine downy mildew pathogen *Plasmopara viticola*

MICHAEL C. FONTAINE,† FREDERICK AUSTERLITZ,† TATIANA GIRAUD,‡ FREDERICK LABBE,‡
DACIANA PAPURA,‡ SYLVIE RICHARD-CERVERA,‡ and FRANÇOIS DELMOTTE‡

*Epidemic, Spatiotemporal, and Evolutionary, UMR 8079 Université Paris-Saclay (Epidemie, Spatiotemporal et Evolution, UMR1079, Oisy Cedex, F-91405, France), 1E30-Anthropologie et Ethnologie, UMR 7208 CNRS, MNHN, UMR 2505 Délai, Rhône Parc Cité, F-72323, France, 1NRA, UMR1065 Santé et Agroécologie de Vignoble, ISVV, F-33603 Vence, Oisy Cedex, France*

Abstract

Biologic invasions can have important ecological, economic and social consequences, particularly when they involve the introduction and spread of plant invasive patho-
gens, as they can threaten natural ecosystems and jeopardize the production of human
food. Examples include the grapevine downy mildew, caused by the oomycyte Plasmo-
para viticola, an invasive species native to North America, introduced into Europe in
the 1870s. We investigated the introduction and spread of this invasive pathogen, by
analysing its genetic structure and diversity in a large sample from European vino-
yards. Populations of *P. viticola* across Europe displayed little genetic diversity,
consistent with the occurrence of a bottleneck at the time of introduction. Bayesian
coalescent analyses revealed a clear population expansion signal in the genetic data.
We detected a weak, but significant, continental-wide population structure, with two
globographically and genetically distinct clusters in Western and Eastern European vino-
yards. Approximate Bayesian computation, analyses of clines of genetic diversity and
of isolation-by-distance patterns provided evidence for a wave of colonization moving
in an early direction across Europe. This is consistent with historical reports, first
mentioning the introduction of the disease in Bordeaux vineyards (France) and sub-
sequently documenting its rapid spread across Europe. This initial introduction in the
west was probably followed by a 'leap-frog' event into Eastern Europe, leading to the
formation of the two genetic clusters we detected. This study shows that recent popu-
lation genetics methods within the Bayesian and coalescence frameworks are extremely
powerful for increasing our understanding of pathogen population dynamics and inva-
sion histories

Keywords: fungi, invasive plant pathogens, microsatellite, phylogenetics, population genetics, recent introduction, Vitis vinifera

Received 18 November 2012; revision received 11 February 2013; accepted 14 February 2013

Introduction

Biologic invasions can have important ecological, eco-
nomic and social consequences (Finlayson et al. 2001,
particularly when they involve the introduction and
spread of pathogens (Anderson et al. 2004). Considerable

Correspondence: Michael C. Fontaine, Fax: +33 774-63-3994
E-mail: mikafontaine@gmail.com

attention is focused on human and animal diseases, but
outbreaks of disease due to invasive pathogens are also
becoming increasingly frequent in plants (Deperin-Lun-
tau et al. 2007). Plant diseases can threaten natural eco-
systems and jeopardize the production of human food.
Carand et al. 2010). Many pathogens of agricultural sys-
tems are believed to be alive in the areas in which they
come damaging epidemics (Finlayson et al. 2001). With
the same crops being cultivated worldwide and the

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Worldwide invasion of *P. viticola* from North America

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Current Biology

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Article

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

Michael C. Fontaine,¹,²,³,⁴,⁵ Frédéric Labbé,¹,²,³ Yann Dussault,¹,² Laurent Delécol,¹,² Sylvie Richert-Chevér,¹
Tatiana Giraud,¹ and François Delécol¹,²

*Oenologie et Ecologie des Végétables (ELEFET), University of Dordrecht, P.O. Box 11103 CC, Oenologie, F-11006 Dordrecht, The Netherlands*
*École Systématique et Évolution, UMR 6075 Université Paris-Saclay, CNRS, Agence ParisTech, Cité 91000, France*
*Laboratoire MIVSEC, Université de Montpellier, CNRS, P.O. 229, Cité de Recherche en Étude et Évolution de la Santé*
*CR255, Unité de Recherche pour l'Développement (IRD), 34040 Montpellier, France*
*GAES, INRA, Bordeaux Sciences Agri, Université de Bordeaux, 32140 Itéracoe d'Oren, France*

These authors contributed equally to this article.

Present address: Department of Biology and Evolution, University of Chicago, Chicago, IL, USA

Previous address: School of Biological and Chemical Sciences, Queen Mary University of London, London, UK

Twitter: @Plasmopora

*E-mail: plasmopora@biol.queensu.ca

¹Lead contact

Correspondence: MichaelCFontaine@leibniz.ac.at

https://doi.org/10.1093/clinbiolint/mba031
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* Cultivated varieties are all highly susceptible

* Strong impact on harvest quantity and quality

* Polycyclic development leading to numerous preventive treatments

* Withdrawal of fungicide molecules

* CC - increased unpredictability of conducive climatic conditions

* Rapid evolution

Research to renew our knowledge to find sustainable management methods alternative to fungicides
### Biofungicides

- peptide aptamer

- RNAi

- extracts, ...

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### Biological control and microbiota

- SynCom

- CBC

### Physical control

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### Plant architecture

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### Removing inoculum

### Genetic resistance

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Conventional breeding programs have created a new generation of disease-resistant varieties with excellent agronomic and organoleptic characteristics.

* 14 INRAE resistant varieties « classée » [total=30]

* 3 000 ha planted in France

* 1400 ha of INRAE var. res.

* -80% of treat. freq. index

The challenges for the future are

* wine quality

* adaptation to CC

* durability of resistance

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new variety
(> 99% vinifera)
# *P. viticola* is quickly adapting to resistant varieties

Peressotti et al. BMC Plant Biology 2010, **10**:147
http://www.biomedcentral.com/1471-2229/10/147

BMC
Plant Biol:

RESEARCH ARTICLE

Open Access

## Breakdown of resistance to grapevine downy mildew upon limited deployment of a resistant variety

Elisa Peressotti<fnref n="1" />,⁴, Sabine Wiedemann-Merdinoglú<fnref n="1" />,<fnref n="2" />, François Delmotte<fnref n="3" />, Diana Bellin⁴,⁶, Gabriele Di Giorgio⁴,⁵
Raffaele Testolin⁴,⁵, Didier Merdinoglú<fnref n="1" />,<fnref n="2" />, Pere Mestre<fnref n="1" />,<fnref n="2" />*

### Abstract

**Background:** Natural disease resistance is a cost-effective and environmentally friendly way of controlling plant disease. Breeding programmes need to make sure that the resistance deployed is effective and durable downy mildew, caused by the Oomycete *Plasmopara viticola*, affects viticulture and it is controlled by Downy mildew resistant grapevine varieties are a promising strategy to control the disease, but the currently restricted to very limited acreages. The arising of resistance-breaking isolates under such deployment of resistant varieties would provide valuable information to design breeding strategies for the development of resistance genes over large acreages whilst reducing the risks of the resistance being observed of heavy downy mildew symptoms on a plant of the resistant variety Bianca, whose resistance conferred by a major gene, provided us with a putative example of emergence of a resistance-breaking interaction between grapevine and *P. viticola*.

**Results:** In this paper we describe the emergence of a *P. viticola* isolate (isolate SL) that specifically *Rpv3*, the major resistance gene carried by Bianca at chromosome 1B. We show that isolate SL has behaviour as two *P. viticola* isolates avirulent on Bianca (isolates SC and SU) when inoculated on sugar or on resistant plants carrying resistances derived from other sources, suggesting there is no fitness to the virulence. Molecular analysis shows that all three isolates are genetically closely related.

**Conclusions:** Our results are the first description of a resistance-breaking isolate in the grapevine/viticulture interaction, and show that, despite the reduced genetic variability of *P. viticola* in Europe compared to the origin and the restricted use of natural resistance in European viticulture, resistance-breaking isolates of monogenic resistances may arise even in cases where deployment of the resistant varieties is limited by acres. Our findings represent a warning call for the use of resistant varieties and an incentive to breeding programmes aiming to optimize durability of the resistances.

### Background

Natural disease resistance is a cost-effective and environment friendly way of controlling plant disease. Breeding programmes aiming to obtain disease resistant varieties have been developed for most plants of economical interest. An important challenge of breeding for disease resistance is durability. Plant disease resistance is defined as durable when it "remains effective during its prolonged and widespread use in an environment

favourable to disease" [1]. The extent to which durable resistance is difficult is highly variable and depends on the disease and the type of disease resistance that most varieties deployed possessing monogenic resistance have been rapidly overcome because of changes in pathogen populations [2,3] (and references therein). As an illustration, [4] lists over 267 resistance genes from 14 pathosystems that proved not to be durable when used as single genes. The durability of the resistance may be improved, among other strategies, by the use of varietal mixtures [5-7] or by pyramiding genes [3]. In any case, a sound knowledge of the biological and genetic components of the pathosystem is important to

BioMed Central

© 2010 Peressotti et al. licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Evolutionary Applications

Open Access

Evolutionary Applications ISSN 1752-4571

ORIGINAL ARTICLE

## Adaptation of a plant pathogen to partial host resistance:

## Phytopathology®

### The characterization of pathotypes in grapevine downy mildew provides insights into the breakdown of Rpv3, Rpv10 and Rpv12 factors in grapevines

Paineau<fnref n="1" />, Isabelle D. Mazet<fnref n="2" />, Sabine Wiedemann-Merdinoglú<fnref n="3" />, Frédéric Fabre<fnref n="1" />,<fnref n="1" />,<fnref n="2" />,<fnref n="3" /> and François Delmotte<fnref n="1" />,⁴

> Grapevine resistances loci have been largely described while the specific efectors detected by grape resistance genes and evolutionary mechanisms leading to resistance breakdowns in *P. viticola* remain entirely unknown.

A standard method for characterizing the virulence *Plasmopara viticola*, the causal agent of grapevine mildew. We used 33 European strains to inoculate six pathotypes carrying the principal factors for resistance breakdown (Rpv1; Rpv3.1; Rpv3.2; Rpv5; Rpv6; Rpv10 and the susceptible *Vitis vinifera* cv. Chardonnay). Reaction, we characterized the level of sporulation lysis and the intensity of the grapevine hypersensitivity by visual score. We propose a definition for reaction of grapevine quantitative resistances combining its. Among the 33 strains analyzed, 28 are virus-1 resistant factors. We identified five differences across the 33 strains analyzed: two pathotypes in single resistance factor (vir3.1 and vir3.2) and six pathotypes overcoming multiple resistance factors; vir3.2.12; vir3.1.3.2.10. Our findings confirm and occurrence of *P. viticola* strains overcoming the pzes (28 strains). We also detected the first breakdown to the Rpv10 by a strain from Germany and of Rpv12 factors by a strain in Hungary. The method proposed here and the associated differences lay the groundwork for the early detection of resistance breakdown in grapevines. This approach will also facilitate the monitoring of the evolution of *P. viticola* populations at large spatial scales. This is an essential step forward to promoting durable management of the resistant grapevine varieties currently available.

Pathotype, Plant-pathogen interaction, *Plasmopara viticola*, Quantitative resistance, Resistance breakdown, Resistance durability

Correspondence: frederic.fabre@inra.fr

& De Toni, is one of the most destructive oomycetes worldwide (1). *P. viticola* is native to North America, where it infects a large number of wild *Vitis* species (2, 3). Following its initial introduction into European vineyards in the 1870s (4, 5), it spread to all major grape-producing regions of the world (6). The Eurasian wine grape *Vitis vinifera* is highly sensitive to downy mildew and the control of this disease is currently largely based on fungicides. Resistance factors from American and Asian *Vitis* species conferring resistance to downy mildew, and known as "Rpv" for resistance to *P. viticola*, are currently being used to breed new disease-resistant varieties. More than 30 genetic factors conferring resistance to downy mildew have been identified (7), but only a small number of these factors are currently used in European breeding programs. The so-called Rpv factors are encoded by major QTL located in genomic regions rich in NBS-LRR-like resistance genes (8, 9). These major resistances display monogenic inheritance, but are phenotypically quantitative (or partial), i.e., *P. viticola* strains develop on these varieties, but to a lesser extent than on wild-type varieties. The most widely used resistance factor is Rpv3, which was selected from the species *V. rupestris* (8, 10, 11). The two major haplotypes used in breeding program are Rpv3.1 (Rpv3<sup>299-279</sup>) identified in the variety 'Seibel 4614', and Rpv3.2 (Rpv3<sup>211-279</sup>) identified in the variety 'Munson' ('Jaeger 70'). The other major resistance factors currently used in breeding programs are Rpv1 (12), from *Muscadinia rotundifolia*, Rpv10 (13), from *V. amurensis* and Rpv12 (14), also from *V. amurensis*. As in many perennial crops, concerns about the durability of these grapevine resistances are magnified by the long duration of breeding schemes (16-17 years (15)) and the lifespan of the plant (about 20-30 years).

Due to its large population size and its capacity for sexual reproduction (16), *P. viticola* has a high evolutionary potential, as illustrated by its rapid adaptation to synthetic fungicides (17-19). The breakdown of the Rpv3.1 factor present in the varieties 'Bianca' and 'Regent' is another example of the rapid adaptation of *P. viticola* to its host (20-22). Indeed, in this context, virulence emerged within five years on at least three independent occasions, in three different wine-

## of their deployment on fungicide use in viticulture

Chantal Wingerter<fnref n="1" />,<fnref n="2" />†, Birgit Eisenmann<fnref n="1" />†, Patricia Weber<fnref n="2" />, Ian Dry<fnref n="3" /> and Jochen Bogs<fnref n="1" />,⁴*

### Abstract

**Background:** The high susceptibility of European grapevine cultivars (*Vitis vinifera*) to downy mildew (*Plasmopara viticola*) leads to the intensive use of fungicides in viticulture. To reduce this input, breeding programs have introgressed resistance loci from wild *Vitis* species into *V. vinifera*, resulting in new fungus-resistant grapevine cultivars (FRC). However, little is known about how these different resistance loci confer resistance and what the potential reduction in fungicide applications are likely to be if these FRCs are deployed. To ensure a durable and sustainable resistance management and breeding, detailed knowledge about the different defense mechanisms mediated by the respective *Rpv* (*Resistance to P. viticola*) resistance loci is essential.

**Results:** A comparison of the resistance mechanisms mediated by the *Rpv3-1*, *Rpv10* and/or *Rpv12-loci* revealed an early onset of programmed cell death (PCD) at 8 hours post infection (hpi) in *Rpv12-cultivars* and 12 hpi in *Rpv10-cultivars*, whereas cell death was delayed in *Rpv3-cultivars* and was not observed until 28 hpi. These temporal differences correlated with an increase in the *trans*-resveratrol level and the formation of hydrogen peroxide shortly before onset

### Associated publication

Paineau M, Mazet ID, Wiedemann-Merdinoglú S, Fabre F, Delmotte F. The Characterization of Pathotypes in Grapevine Downy Mildew Provides Insights into the Breakdown of Rpv3, Rpv10, and Rpv12 Factors in Grapevines. Phytopathology. 2022 Nov;112(11):2329-2340. doi:10.1094/PHYTO-11-21-0458-R.

### Introduction

Grapevine downy mildew, caused by the obligate biotrophic oomycete *Plasmopara viticola* (Berk. & M. A. Curt.) Berl.

<footnote>* Correspondence: pere.mestre@colmar.inra.fr</footnote>

<footnote n="1">¹INRA, UMR1131 Santé de la Vigne et Qualité du Vin, F-68000 Colmar, France</footnote>

<footnote n="1">¹INRAE, Bordeaux Sciences Agr., SAVE, ISVU, Villeneuve d'Orron, F-33140, France</footnote>

<footnote n="2">²INRAE, Université de Strasbourg, SVOV, Colmar, F-68000, France</footnote>

<footnote n="3">³These authors contributed equally to the article.</footnote>
# First identification of Avr genes involved in the interaction with grapevine resistance

* Rpv3.1 is the most largely deployed resistance

* It triggers localized **necrosis** similar to effector-triggered immunity

* It was recently mapped to a locus containing two NB-LRR genes

* Rapid adaptation pf *Pvi* has been reported in several geographically distant populations over the past decades (Germany, Hungary, Italy, France, etc.)

> It suggests a gene-for-gene interaction between grapevine resistance genes and unidentified avr genes

Paineau et al., 2024,
*New Phytol*,
243(4), 1490-1505

<figure><img src="image_46.png" /></figure>

## Population genomics - GWAS

<figure><img src="image_47.png" /><figcaption>virulent strains
from different regions</figcaption></figure>

<figure><img src="image_48.png" /><figcaption>Virulence alleles</figcaption></figure>

<figure><img src="image_49.png" /></figure>
<figure><img src="image_50.png" /></figure>

<figure><img src="image_51.png" /></figure>

<figure><img src="image_52.png" /></figure>
Virulence is significantly associated to a genomic region of P. viticola. A large deletion was detected in the region of interest.

<figure><img src="image_53.png" /></figure>
The candidate genes (g164, g165) encode putative effector proteins

* Protein size of ~880 amino acids !

* Presence of a **signal peptide** (EER) => secreted proteins

* Structural similarity with two **RXLRs** effectors of *Phytophthora*

* Agrobacterium-mediated transient expression into leaves of Regent (Rpv3.1+) and the susceptible variety Syrah Both genes induced **cell death in Regent but not in Syrah.**

<figure><img src="image_54.png" /></figure>
# Identification of Avr genes involved in the interaction with Rpv10 and Rpv12 resistances

## New breakdown of resistance for Rpv10 and Rpv12

- Study of genetic determinants of plant-pathogen interactions

- Integrate population genetics approaches to elucidate the evolutionary factors driving the emergence of virulence

Parallel adaptation and admixture drive the evolution of virulence in the grapevine downy mildew pathogen

Dvorak et al., 2025, *bioRxiv*

<figure><img src="image_55.png" /></figure>

## Quantitative genomic approach

<figure><img src="image_56.png" /></figure>
<figure><img src="image_57.png" /><figcaption>One QTL determines virulence towards Rpv12 associated with homozygous deletions of RXLR genes</figcaption></figure>
One QTL determines virulence towards Rpv12 in the genome of *P. viticola*

* The virulent parent has a **large homozygous deletion** encompassing 3 RXLR genes in the locus identified

* Different deletions sizes : Rpv12 breakdown results from **parallel local adaptations**

<figure><img src="image_58.png" /></figure>
Strains overcoming Rpv10 carry an American admixture

* Strains overcoming Rpv10 all originate from the Upper Rhine Plain

* They show variable level of admixture with a North American genetic background

Proportion of cluster

<figure><img src="image_59.png" /></figure>
# Virulence twoards R genes : distinct mechanisms and evolutionary pathways

AvrRpv3.1, AvrRpv12

<figure><img src="image_60.png" /></figure>

Rpv3.1, Rpv12

* Breakdown of **Rpv3.1** **Rpv12** by **loss of Avr** factor (recessive)

* **Parallel adaptations** upon the recent deployment in Europe

<figure><img src="image_61.png" /></figure>

AvrRpv10

S-AvrRpv10

<figure><img src="image_62.png" /></figure>

Rpv10

* Partial breakdown of **Rpv10** by a potential **gain of suppressor** (dominant)

* Adaptation facilitated by **admixture** (introduction of new alleles in Europe)

<figure><img src="image_63.png" /></figure>
# A European-wide monitoring of grapevine disease-resistant varieties

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Grapebreed
4 IPM

> 60 parcels in production are included at the EU level

In France (2024)

- 186 fields in production

- >100 localities

- 36 partners

- 32 varieties

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Oscar·EU

European Observatory for the Deployment
of Disease Resistant Grapevine Varieties

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In progress : assess real-time
monitoring of virulence of downy
mildew populations
facing resistant varieties
## Biofungicides

* peptide aptamer

* RNAi

* Extracts

* ...

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## Biological control and microbiota

* SynCom

* CBC

Physical control

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Plant architecture

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© inrae

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Genetic resistance

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Removing inoculum
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Large epidemics in autumn, whatever the epidemics during the season

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In 2024, oospore formation takes place between September 29 and October 16
Develop a prophylaxis targeting the obligate sexual cycle of the pathogen

disrupting
sexual cycle by

Limiting
primary
infections

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Removing
infected
crop residues

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Limiting
oospores
formation

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We developed a new **ddPCR method** for quantifying **oospores reservoirs in vineyard**

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feb. 2022, 318 soil
samples collected

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Merlot plot

0,18 ha

Soil 'sablo-graveleux'

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* High spatial variability within plots

* Spatial autocorrelation < 10 meters

* Effect of row distribution

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=> 5 times more inoculum
(oospores) on the row

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# An experiment to assess the efficiency of removing primary inoculum on grapevine downy mildew epidemics

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'Prophylaxis' plot :
grapevine leaves are
extracted from the field

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Control
plot
A reduction in the amount of primary inoculum in the soil

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> 50% reduction in downy mildew on leaves and bunches in 2024

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Gene
resistar

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Genetic
resistance

Micro-
biota

Bio-
Fungi-
cides

Fungicides
like aptamer
units

Removing
inoculum

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Prophylaxis

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Copper

Microbial-based
biological control

Biological
control and
microbiota

- SynCom

- CBC

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Cultural
practices

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Plant
architecture

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Physical
methods
Carole Couture, inrae

Laurent Delière, inrae

Isabelle Demeaux, inrae

Frédéric Fabre, inrae

Pere Mestre, inrae

Anne-Sophie Miclot, inrae

Charlotte Poyedebat, bsa

Benoit Laurent - ifv

Xavier Burgun ifv

Lucie Andrianasolonirina

Paige Breen

Eva Courchinoux

Yann Dussert

Etienne Dvorak

Manon Paineau

Laura Marolleau

Julie Martinez

Marie Rodriguez

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Thank you for your attention