QTLs related to berry acidity identified in a wine grapevine population grown in warm weather

The optimal balance between sugar and acidity is an essential criterion to elaborate equilibrated and stable wines. The aim of this study was to locate quantitative trait loci (QTLs) for these traits using an F1 population derived from Monastrell and Syrah wine cultivars. Several parameters related to acidity were evaluated during six consecutive years by measuring total soluble solids, total acidity, malic acid, and tartaric acid. Three genetic maps were developed using 104 SSR (simple sequence repeat) and 146 SNP (single-nucleotide polymorphism) markers. The consensus map covered 1174 cM with 238 markers assembled in 19 linkage groups (LGs). Significant QTLs at the genome-wide level were detected, and, although they exhibited a large degree of instability from year to year, QTLs for the ratio of soluble solids to acidity (LG2) and malic acid (LG8) and the ratio of tartaric to malic acid (LG8) were stable in at least 2 years. Several annotated genes involved in sugar and acidity pathways co-located with the confidence intervals of these QTLs and are proposed as putative candidate genes for future studies of these traits