The use of molecular markers for pyramiding resistance genes in grapevine breeding

The practical application of pyramiding resistance genes by the use of molecular markers was investigated in a F1 progeny derived from the cross of VHR 3082-1-42 x 'Regent'. VHR 3082-1-42 is a cross between Museadinia rotundifolia x Vitis vinifera, backcrossed another four times with V. vinifera (PAUQUET et al. 2001). It carries the Run1-gene which causes resistance to powdery mildew and the Rpv1-gene which is related to resistance against downy mildew. Both genes were introduced from Muscadinia rotundifolia (Bou-QUET et al. 2000; Wiedemann-Merdinoglu et aL 2006). 'Regent' is a new cultivar with quantitative resistance against downy and powdery mildew (Eibach and Topfer 2003) released in Germany in 1996 for commercial use. 119 individuals of the F1 progeny were screened with a molecular marker for the Run1-gene (DONALD et aL 2002), with two SSR-markers for the Rpv1-gene (Wiedeniann-Merdinoglu et al. 2006) and with several markers from 'Regent'that showed good correlation to powdery and downy mildew resistance (Zyprian et aL 2002, Salakhutdinov et al. 2003, Akkurt 2004, Fischer et aL 2004, Akkurt et aL 2007). Phenotypic evaluation for downy mildew resistance was done by artificial inoculation of leaf discs, and for powdery mildew by natural infection in a greenhouse. Comparison of the phenotypie data with the results of the molecular marker analyses showed a clear correlation between the degree of resistance and the presence of the resistance related alleles. According to the phenotypic data, 20 genotypes of the offspring were free of powdery and downy mildew infections. Based on a marker-assisted evaluation, out of these 20 genotypes a subset of four carried all the resistance related alleles for powdery and downy mildew indicating that resistance genes from both parents were effectively combined.