Quantitative genetic analysis of berry firmness in table grape (Vitis vinifera L.)

Berry texture is a determinant quality trait in the breeding of new table grape varieties. We present the first mapping quantitative trait loci (QTL) results for berry firmness in table grape. Two segregating progenies, Muscat Hamburg × Sugraone (153 offspring) and Ruby Seedless × Moscatuel (78 offspring), were evaluated for this trait during two and four productive seasons, respectively. Firmness was scored at harvest as the force (newtons) required for a 20 % deformation of the berries. Parental and consensus genetic maps were built for each population. QTL analyses revealed a complex genetic control of firmness. Significant QTLs at genome-wide level were detected in seven genomic regions on linkage groups (LGs) 1, 4, 5, 9, 10, 13, and 18, individually explaining up to 19.8 % of the total phenotypic variance. The combined effect of all the QTLs detected in one season explained up to 44.5 % of the total phenotypic variance. Some annotated genes colocating with the LOD-1 support intervals of those QTLs are proposed as putative candidate genes that might be responsible for the QTLs that affect berry firmness.