Evaluation of grapevine resistance to downy and powdery mildew in a population segregating for run1 and rpv1 resistance genes

International audience; In this paper we present the behaviour of a population of vine segregating for several sources of resistance to powdery (PM) and downy mildews (DM). Resistance genes from Muscadinia and Vitis American species were introduced in a Vitis vinifera genetic background. Resistance to both pathogens was assessed in bioassays under controlled inoculations with two isolates for PM and three isolates for DM and in greenhouse or field experiments under natural infections. 19 out of 38 segregant genotypes were identified as totally resistant to PM on leaves and partially resistant to DM on both leaves and bunches. All these genotypes presented a level of damage satisfactory in an IPM context. There is no evidence to say that the resistance genes are expressed in bunches. However, the descriptors of resistance used in the bioassay, can be used to select with a good accuracy genotypes with an acceptable level of damage on bunches. The link between resistance to powdery mildew and downy mildew suggest that resistance in harvestable genotypes is coming from Muscadinia (Rpv1 and Run1).