Pyramiding of resistance alleles to grape powdery mildew assisted by molecular markers.

Disease resistance gene pyramiding is a widely used strategy to enhance resistance durability. Marker-assisted selection (MAS) was applied to pyramide the alleles Run1 and Ren3, which confer resistance against grape powdery mildew (Erysiphe necator). Two F1 full-sibs carrying Run1 and Ren3 in heterozygosity were selfed to develop the breeding populations used in the analysis. From the 637 genotyped plants, 313 (50.6%) had the Run1 and Ren3 pyramided. Seven (1.1%) of them exhibited the two resistance alleles in homozygosity. Plants without any resistance alleles had the highest disease severity (X̅ = 7.3), while the ones with the Run1 allele both in homozygosity and heterozygosity were highly resistant (X̅ = 1.5). Similar level of resistance was observed in the plants containing Run1 and Ren3 pyramided (X̅ = 1.3). Plants containing Run1 and Ren3 pyramided in homozygosity are important genetic resources for grape breeding programs in Brazil. [ABSTRACT FROM AUTHOR]