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Objectives

In the context of creating disease-resistant grapevine varieties, knowledge of the genetic and molecular basis of resistance, as well as its interaction with other biotic and abiotic factors, is essential for the sustainable management of grapevine pests.

Approaches and resources

Identification of sources of resistance and study of the genetic basis of resistance through genetic mapping

Once disease-resistant genotypes have been identified, crossing them with susceptible genotypes gives rise to segregated populations whose phenotyping and genotyping enable us to :

• identify the genetic basis of resistance
• map resistance genes
• define molecular markers to be used for marker-assisted selection (MAS) during the process of introgression and varietal creation.

These approaches are used in the case of resistance to cryptogamic diseases (mildew, powdery mildew, black rot) and to the virus of court-noué.

Diversification of resistance mechanisms: search for recessive resistance genes

All the downy mildew and powdery mildew resistance genes whose genetic bases have been identified are dominant genes mapped on regions of the genome corresponding to clusters of resistance genes of the NLR (NOD-Like Receptor) type. NLR gene products recognize pathogen proteins and activate defense responses. By their very nature, NLR genes are not very durable. The availability of recessive resistance genes would make it possible to construct varieties combining different types of resistance, which in turn would help to reduce the risk of bypass.

Two approaches are used to search for recessive resistance genes. The first is based on exploiting the genetic diversity of grapevines, either by studying the genetic variability of candidate resistance genes in a collection of grapevine accessions, or by screening self-pollinated populations of grapevine varieties for disease resistance; the second is based on modifying candidate resistance genes using gene-editing tools.

Molecular analysis of resistance: gene cloning, identification of Avr genes for resistance genes

Pathogen genes whose products are recognized by NLR-type resistance gene products are called avirulence genes. The identification and molecular characterization of NLR-Avr pairs is important both for understanding the mechanism of resistance and for predicting the risk of resistance bypass and monitoring virulence evolution. The identification of resistance genes employs a cloning strategy based on mapping, while the search for Avr genes uses an effectoromics strategy, based on the hypothesis that resistance genes recognize a pathogen effector and that transient expression of this effector in plants carrying the resistance gene results in the induction of cell death. Effectoromics is useful for identifying Avr genes corresponding to resistance genes for which the absence of bypassing strains prevents the use of other strategies, such as association genetics or genetic mapping.

Impact of biotic and abiotic factors on the efficacy of disease resistance genes

It has been shown in several pathosystems that the expression of resistance can be modulated by biotic or abiotic factors. In grapevines, hypotheses involving interactions between factors can be put forward to explain variations in the level of susceptibility to a given fungal pathogen depending on the level of nitrogen nutrition, viral health status or the presence of another fungus.

Staff

GAV team

• Anne ALAIS
• Marie Annick DORNE
• Vincent DUMAS
• Maria Victoria GARCIA-HERNANDEZ
• Marie-Céline LACOMBE
• Laurie MARSAN
• Raymond MASSON
• Pere MESTRE
• Alessandro PIRES-RAMOS
• Marie Christine PIRON
• Tyrone POSSAMAI
• Emilce PRADO
• Lukasz TARKOWSKI
• Aurélie UMAR-FARUK
• Sabine WIEDEMANN

GMV team

• Camille RUSTENHOLZ
• Amandine VELT

ViVe team

• Gérard DEMANGEAT
• Samia DJENNANE
• Claude GERTZ
• Olivier LEMAIRE
• Sophie VERDUN

Funding

INRAE BAP Department

VITAE: Cultivating vines without pesticides: towards agroecological viticultural socio-ecosystems

• Funding: Programme Prioritaire de Recherche Cultiver et Protéger Autrement (PPR-CPA)
• Duration: 2021-2026
• Contact: Pere Mestre

GrapeBreed4IPM: Varietal innovation as a lever for integrated pest management in viticulture

• Funding: Horizon Europe
• Duration: 2024-2028
• Contact: Komlan Avia

Results

• Identification of a first gene for resistance to the short-knotted virus (Djennane et al, 2021). The identification of a recessive resistance gene to the short-knotted virus in the Riesling variety is a first in grapevines and opens the door to the use of genetic resistance to combat this disease.
• Identification of a powdery mildew resistance QTL in V. vinifera (Possamai et al, 2021). Unlike resistance genes identified in other species, the identification of a powdery mildew resistance gene in a V. vinifera variety enables its rapid integration into breeding programs.
• Identification of the P. viticola effector repertoire and functional characterization (Combier et al, 2019; 2021). We have highlighted the existence of a class of effectors in P. viticola that is characteristic of obligate biotrophic oomycetes, also known as downy mildews.