Downy mildew caused by the oomycetePlasmopara viticolais one of the most important diseases affecting grapevine. Resistant varieties are an environmentally-friendly tool to control grapevine downy mildew. Efficient breeding for durable resistance requires knowledge of the underlying mechanisms. Here we aimed at identifying the molecular basis ofRpv2, a gene for extreme resistance to downy mildew derived fromVitis rotundifolia, and at characterizing its effect on pathogen development. Individuals from two populations segregating forRpv2were evaluated for resistance to downy mildew and genotyped. Following genetic mapping, markers flankingRpv2were used to screen new populations and identify recombinant individuals. Sequencing of recombinants andin silicochromosome painting was used to reduce the interval containingRpv2. Comparative genomics inside theVitaceae, involvingde novoassembly of theV. rotundifoliaRegale genome, allowed narrowing-down the list of candidate genes. We restrictRpv2to a 250 kb genomic region that contains two resistance genes of the NLR type. Comparative genomics analyses could not find orthologs of both NLRs in the otherVitisspecies studied. We also show thatRpv2-mediated resistance leads to pathogen arrest early in the infection cycle. Our results show thatRpv2belongs to the NLR family of resistance genes, contributing thus to understand the potential and risks of its use in breeding programs and suggesting that combining NLR-type genes may lead to durable resistance
KEY MESSAGE
TheRpv2locus for extreme resistance to grapevine downy mildew is mapped to a 250 kb genomic region containing two NLR-type genes specific toV. rotundifolia.