Highlights 2025 INRAE BAP Division

Downy mildew-resistant vines: defeated loci may compromise the effectiveness of other major resistance genes
The creation of new grapevine varieties that are naturally resistant to downy mildew is an essential strategy for reducing the use of fungicides in viticulture, a strategy that has demonstrated its potential thanks to the INRAE-ResDur breeding program. In this context, the combination of several downy mildew resistance genes in a single grapevine variety (pyramiding) is used to increase the durability of resistance. However, while pyramiding provides increased resistance in the vast majority of cases, resistance loci that are defeated by certain strains of downy mildew can act as Trojan horses, compromising the resistance provided by other major loci in certain pyramiding situations. The discovery of potentially negative interactions between major resistance loci therefore calls for further research to identify the most promising combinations of resistance genes for optimal resistance durability.

Publication : bioRxiv doi.org/10.1101/2025.04.25.650562
Contact : Philippe Hugueney

Identification of an NBS-LRR gene conferring total resistance to grapevine downy mildew
Viticulture is an important component of the French economy. Downy mildew of grapevine is one of the most damaging diseases for viticulture. Resistant varieties represent the most credible alternative to the use of pesticides to combat downy mildew. Because grapevine cultivated in Europe (Vitis vinifera) is susceptible, resistance must be introduced from other Vitis species. The Rpv2 gene, originating from Vitis rotundifolia, confers complete resistance to grapevine downy mildew. Using genetic mapping, sequencing of recombinant individuals, in silico chromosome painting, and comparative genomics within the Vitaceae family, Rpv2 has been restricted to a 250 kb genomic region containing two NBS-LRR resistance genes. This work also shows that Rpv2-mediated resistance leads to the restriction of pathogen growth early in the infection cycle. These results help to understand the benefits and risks associated with the use of Rpv2 in breeding programs.

Publication : Theoretical and Applied Genetics doi.org/10.1007/s00122-025-04959-z
Contacts : Pere Mestre, Camille Rustenholz

Discovery of a locus associated with susceptibility to Esca in grapevine

Esca is the most destructive and prevalent grapevine trunk disease. The chronic infections and vine mortality caused by Esca syndrome result in significant economic losses and endanger the sustainability of vineyards worldwide. Although differences in susceptibility to Esca have already been observed between grapevine varieties, no genetic factors explaining these variations had been identified until now. Based on destructive phenotyping of a sixteen-year-old Riesling × Gewurztraminer progeny a locus on chromosome 1 of the Gewurztraminer grape variety linked to variations in trunk necrosis associated with Esca was identified. This locus, named ‘Esca Necrosis Susceptibility 1’ (ENS1), is the first genetic factor identified to be linked to Esca.

Publication: Plant Disease doi.org/10.1094/PDIS-06-24-1258-RE
Contact: Guillaume Arnold