The Fondazione Edmund Mach grapevine breeding program for downy and powdery mildew resistances: Toward a green viticulture

During the last decade, besides the emerging need for innovation raised by grapevine growers, the quest for sustainable viticulture has been addressed through the development of new cultivars (mid-)resistant to the major pathogens that challenge grapes in temperate-humid climates. To this end, a double-step breeding program has been undertaken by the Fondazione Edmund Mach (FEM). During the initial scouting phase, a total of 264 accessions acquired from (non-)European breeding programs, an Italian private breeding platform and wild-collected in northeastern America were studied. Most individuals were phenotyped for downy and powdery mildew resistance, while all were genetically characterized. First, nine reference microsatellite (simple sequence repeat; SSR) markers were used for true-to-type identification through international and private databases, where feasible. Second, in order to validate the available pedigree information and to infer new relationships, 50 informative SSRs were analyzed and employed for parentage analysis. Moreover, all studied accessions were screened at 12 exploitable disease resistance-associated (R) loci derived from Vitis spp. and described in the literature; this novel “all vs. all” approach allowed the discovery of unanticipated R-loci combinations in traditionally bred material. Moreover, the distribution of loci related to downy (Rpv) and powdery (Run/Ren) mildew resistance and the field response unveiled potentially novel and exclusive genetic resources. During the following operational phase, a marker-assisted breeding program developed, taking advantage of the preparatory information. At present, 32% of the selected genotypes stack two Rpv and two Run/Ren loci, while 6% convey three Rpv and three Run/Ren loci. Currently, several genotypes carrying up to seven R-loci are under selection.