Identification of Breeding Signatures in Grapevine Hybrids, Donors of Resistances against Downy and Powdery Mildew

Grapevine (Vitis vinifera L.) is one of the most valuable crops in the world, but has been often plagued by encountering new parasites that still represent a major constraint, such as downy (DM) and powdery (PM) mildew. Nowadays, growers are still obliged to recur to a massive use of pesticides to prevent serious yield loss. In consequence, the research applied to breeding for resistance and the deployment of new resistant grapevine varieties are strongly encouraged as a step towards sustainable agriculture. In this study, we focus on the genetic characterization of numerous Vitis hybrids, donors of resistance to DM and/or PM, in order to identify selection signatures. In particular, 86 hybrids of European origin and of 100 American hybrids, along with 30 related V. vinifera varieties, have been genotyped at 70 SSR loci. Based on the SSR profiles, the historical pedigree information has been checked and, following the trueness-to-type validation for most of the studied hybrids, the Identity By Descent (IBD) analysis has been performed, tracing the allelic flow through the successive generations. Here we report preliminary results about the identification of non-vinifera genomic intervals retained into the vinifera background. Subsequently, the genotyping analysis will be extended to the other 12 chromosomes (120 SSRs) and possibly to new crucial genotypes. The final result of this study will be the release of molecular markers valuable for grapevine Marker-Assisted Breeding (MAB) approach, upon their validation in ad hoc segregating populations.