High-density genetic mapping and linalool content-related QTL analysis in a white wine F₁ population

Linalool, a monoterpene, is one of the most important aroma compounds in grapevine leading to a floral fragrance in ripe fruits and later wines. Total concentrations of free linalool were measured in standardized wine samples during four consecutive years in 150 genotypes of a 'Calardis Musqué' × 'Villard Blanc' cross segregating for this trait. A high-density genotyping-by-sequencing (GBS) based genetic map with 2260 markers (about 80% full-informative) was used to detect five stable major quantitative trait loci (QTL) related to linalool content. The major QTL on chromosome 2 co-located with a 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) synthase and a putative Geraniol 8-hydroxylase, both promising candidate genes coding for enzymes of the isoprenoid biosynthesis pathway. Two minor QTLs on chromosome 10 and 11 are both colocated with putative terpene biosynthesis-related genes. The locus on chromosome 11 includes a 1-deoxy-D-xylulose-5-phosphate synthase (DXS) gene, coding for the first enzyme of the plastidial non-mevalonate (MEP) pathway. The QTL on chromosome 16 and 18 overlap with the already described véraison loci Ver1 and Ver2 and are therefore considered to have an indirect ripening effect to linalool content. As linalool starts to accumulate with the onset of véraison a presumable elongated ripening period may have the positive effect on linalool formation based on our sampling procedure. These promising results provide the basis for marker development usable in marker-assisted selection (MAS) programs and expand our knowledge of key factors in monoterpene biosynthesis beyond classical muscat cultivars.