INRA-ResDur: the French grapevine breeding programme for durable resistance to downy and powdery mildew

The current strategy to control grapevine downy and powdery mildews relies on chemical treatments. The most promising option to reduce the need for fungicides in viticulture is the use of resistant cultivars. This is why a new breeding programme called INRA-ResDur was launched in 2000 to create cultivars with durable resistance to downy and powdery mildews and with berry quality suitable for the production of high-quality wines. Various American and Asian sources of resistance have been known for a long time. During the last decade, intense genetic analyses of some of them have unveiled several resistance loci. However, resistance breakdown has already been observed for the locus Rpv3 (resistance to Plasmopara viticola carried by the resistant cultivar ‘Bianca’) and for the locus Run1 (resistance to Uncinula necator derived from Vitis rotundifolia). To ensure the durability of resistance, the INRA-ResDur programme used marker-assisted selection (MAS) to stack resistance factors derived from multiple sources. Thus, MAS allowed us to follow six resistance loci, Rpv1, Rpv3 and Rpv10 for downy mildew and, Run1, Ren3 and Ren3.2 for powdery mildew. This strategy led to the development of candidate cultivars bearing not only one but two or three genes to control each disease. Four new resistant cultivars, ‘Artaban’, ‘Floreal’, ‘Vidoc’ and ‘Voltis’, were registered in 2018, and a set of about 20 additional cultivars should be released by 2024. This project is a result of collaborations between INRA and IFV, the French Vine and Wine Institute, as well as other European breeding institutes.