The Use of Molecular Markers for Pyramidizing Resistance Genes in Grapevine Breeding

The practical application of pyramidizing resistance genes by the use of molecular markers was investigated in an F1 progeny derived from the cross of 'VHR 3082-1-42' x 'Regent'. 'VHR 3082-1-42' was derived from a cross between Muscadinia rotundifolia x V. vinifera, backcrossed another four times with V. vinifera (Pauquet et al., 2001). It carries the Run1 gene which causes resistance to powdery mildew and was introduced from Muscadinia rotundifolia (Bouquet et al., 2000). 'Regent' is a new cultivar with partial resistance against downy and powdery mildew (Eibach and Topfer, 2003) released in Germany in 1996 for commercial growing. 119 individuals of the F1 progeny were screened with a molecular marker for the Run1 gene (Donald et al., 2002) and with several markers from 'Regent' that showed good correlation to powdery and downy mildew resistance in a mapping population derived from a cross between 'Regent' and 'Lemberger' (Zyprian et al., 2002; Salakhutdinov et al., 2003, Akkurt, 2004; Fischer et al., 2004; Akkurt et al., 2006). Phenotypical 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 phenotypical data with the genotypes at the molecular markers showed a clear correlation between the degree of resistance and the presence of alleles shown to be linked to the resistance in the previous study. According to the phenotypical data, 20 genotypes of the offspring did not show any powdery and downy mildew infection. Out of these 20 genotypes, a subset of four genotypes carried all the tested alleles linked to resistance to powdery and downy mildew, indicating that the resistance genes from both parents are pyramidized. A marker assisted selection scheme is proposed.