Identification of QTLs for Seedlessness, Berry Size, and Ripening Date in a Seedless x Seedless Table Grape Progeny

A full-sibling F1 population of 144 individuals from a cross of Ruby Seedless x Thompson Seedless (<i>Vitis vinifera</i> L.) was used to generate a consensus genetic map based on 154 markers (105 SSRs, 37 AFLPs, five ISSRs, one RAPD, four SCARs, and two phenotypic markers) distributed across 19 linkage groups covering 1,340 cM. The following traits were evaluated for later quantitative trait loci (QTL) analysis for seedlessness: number of seeds, total fresh and dry weight of seed and seed traces, berry size and weight, and ripening dates. A QTL with a major effect (K up to 45%) for seedlessness subtraits was found on linkage group 18. QTLs for berry size, berry weight, and ripening date were found in the same location, suggesting a pleiotropic effect. Seedless berries were smaller and had an earlier ripening date. Four other minor QTLs for seedless were found in linkage groups 4, 8, 15, and 16. These results are consistent with previous studies and reflect the quantitative and qualitative nature of this complex trait.