IDENTIFICATION OF GENES RELATED TO BIOTIC STRESS RESISTANCE IN GRAPEVINE

Downy mildew (Plasmopara viticola) and powdery mildew (Erysiphe necator) are some of the biggest threats affecting grapevine production. Part of the solution to the problem could be the development of breeding programs for resistant varieties. In this context, the aim of this PhD project has been the identification of new resistance and susceptibility genes for future exploitation in the development of grapevine resistant varieties. To do that, the project has been divided in different work packages. The first one was about the genome assembly and study of Mgaloblishvili, the first identified downy mildew resistant Vitis vinifera variety. In the genome, three resistance loci, Rpv29, Rpv30 and Rpv31, were successfully identified and analyzed for gene content and expression during P. viticola infection. The second work package was about the validation assay of VviLBDIf7, a candidate gene of susceptibility to downy mildew. Similarly, the third work package was dedicated to the screening for new candidate genes of susceptibility to downy mildew, starting from a previously published RNA-sequencing experiment and focusing on nitrogen metabolism. Both in the second and third work package a transient RNA interference (RNAi) approach based on the exogenous application of dsRNA was applied, and VviLBDIf7 was proved to be a promising candidate S gene. Finally, the fourth work package was about a Genome Wide Association Study (GWAS) for the identification of new resistance loci to downy mildew and powdery mildew. The study was conducted on a population of V. vinifera varieties originated in the Caucasus and neighboring regions, one of the two domestication centers of grapevine. Four new loci where identified and analyzed for gene content. Interesting new candidate genes of resistance were hypothesized. All together, these results will contribute to the increase of knowledge on plant-pathogen interaction and, hopefully, to viticulture sustainable disease management.