Selection of grapevine hybrids resistant to fungal diseases

Powdery and downy mildew are two fungal grapevine diseases caused by the pathogens Erysiphe necator (syn. Uncinula necator) and Plasmopora viticola, respectively. Its control entails a high economic cost and a great environmental impact. The identification of wild species of Vitis with different degrees of natural resistance to these diseases allows the introduction of these features in new cultivars of grapevine. The use of molecular markers makes possible to select those hybrids that carry alleles of resistance at an early stage, speeding up the breeding process. It is highly desirable to combine as many different resistance factors as possible into one enhanced line, because the presence of one resistance locus may not be sufficient for a durable response. Our study consisted of marker-assisted selection of a progeny obtained by crossing ‘Regent’ (a cultivar obtained in Germany) and hybrid ‘It 12-3-73’ (a hybrid obtained in our breeding program), carrying the Ren3 and Rpv3 loci that confer resistance to powdery and downy mildew respectively. In total, 596 hybrids have been analysed with different molecular markers linked to the Ren3 and Rpv3 loci. Of the 596 hybrids analysed, 208 (35%) have inherited the alleles of resistance to powdery and downy mildew, 263 (44%) only to powdery mildew and 51 (9%) to downy mildew.