QTLs for muscat flavor and monoterpenic odorant content in grapevine (Vitis vinifera L.)

Little is known about the genetic determinism of muscat flavor in grape, although this trait is of major importance for table grape breeding. We therefore performed a search for QTLs (Quantitative Trait Loci) of both muscat score and berry content in the three main free monoterpene alcohols potentially involved, linalool, nerol and geraniol, based on two years of measures. Parental and consensus framework genetic maps of the cross MTP2687-85 (Olivette x Ribol) x Muscat of Hamburg were built after genotyping the 174 offspring for 139 well-scattered SSR markers. The female, male and consensus framework maps spanned 935, 1365 and 1267 cM, respectively. For QTL detection, simple and composite interval mapping were performed, as well as non parametric Kruskal-Wallis tests. QTLs for muscat score were found on linkage groups (LGs) 1, 5 and 7. For the three ln-transformed monoterpene contents, QTLs with major effects (explaining 17-55 % of total phenotypic variance) were found to be colocated on LG 5, on the male and consensus maps in both years. One additional QTL was found for linalool on LG 2, on female and consensus maps, as well as other colocated ones for nerol and geraniol on LG 13, on male and consensus maps. These additional QTLs had lower effects (9-25%). The contribution of these results to the knowledge of muscat aroma genetic determinism is discussed, as well as their potential usefulness for marker assisted breeding of new aromatic grape varieties.