Quantitative trait loci for the response to gibberellic acid of berry size and seed mass in tablegrape (Vitis vinifera L.)

Background and Aims: Bioactive gibberellins are commonly applied to increase the size of berries in seedless tablegrapes. The genetic determinants for the response of berry size to gibberellic acid (GA3) were investigated in a progeny (n = 137) of Ruby Seedless × Sultanina. Methods and Results: Seed and berry size-related traits were measured at harvest (18°Brix). Heritability was high (∼79%) for all traits under study, especially seed dry mass (>90%). All these traits responded to GA3 and showed interaction between genotype and treatment (g × GA3). Based on quantitative trait loci (QTL) analysis and the grapevine reference genome, we identified about 200 annotated genes located in the corresponding confidence intervals in linkage groups 2 and 18. Nineteen of these genes were selected for further characterisation because of their possible participation in g × GA 3. Conclusions: The response to GA3 has an important genetic basis which is given by QTLs localised on linkage groups 2 and 18. Under GA3 treatment, the seed loses its genetic control on berry size given by its major QTLs, indicating a possible interaction between this genetic determinant and GA3. Despite the masking effect, VvAGL11 is associated with the intensity of the response to GA3. Significance of the Study: These results indicate the complex role of g × GA3 at the genetic level in the control of berry size.