Marker-assisted selection for two dominant powdery mildew resistance genes introgressed into a hybrid grape population

Molecular marker-assisted selection (MAS) was carried out to track the inheritance of Run1 and Ren1, two dominant powdery mildew resistance genes that originate from different genetic resources. The Run1 locus was introgressed from a Muscadinia rotundifolia × Vitis vinifera BC₄ hybrid plant derived from a recurrent pseudo-backcross breeding scheme, whereas the Ren1 locus was introgressed from the powdery mildew-resistant V. vinifera L. variety Kishmish vatkana. Introduction of the Ren1 resistance gene of V. vinifera origin into the breeding program makes possible the long-term defence of the dominant Run1 gene. Using a BC₅ (BC₄ × Kishmish vatkana) hybrid progeny consisting of 441 plants and applying several SSR and BAC-derived CB markers, we demonstrated that the powdery mildew-resistant phenotype co-segregated with the presence of at least one resistance locus-linked marker in the genome. Our data also corroborated earlier findings that the M. rotundifolia-derived Rpv1 and Run1 loci are closely linked. To further streamline the selection process, we developed a multiplex PCR- and agarose gel electrophoresis-based method for the simultaneous detection of both Run1 and Ren1. The results illustrate that MAS offers a rapid and accurate method to select hybrid genotypes that combine multiple loci of interest in grape.