Identification of causal mutations of metabolic QTLs associated to grape and wine flavor

Secondary metabolites produced in grapevine berries play an essential role in high-quality wines and also contribute to the quality of table grapes. Some of the most prevalent wine odor constituents are monoterpenoids which biosynthesis via the plastidial methyl-erythritol-phosphate (MEP) pathway has been demonstrated in grapevine. Based on a double pseudo-testcross mapping strategy, we detected a major QTL on LG 5 for linalool, nerol and geraniol content in grapevine berries at ripening time, and also an additional QTL for linalool on LG 10. Further testing indicated that gain-of-function mutations in the structural gene of the MEP pathway 1-deoxy-D-xylulose-5-phosphate synthase (VvDXS1) - colocalized with the mQTL on chromosome 5 - are the major determinants for terpenoid accumulation in Muscat grape varieties and have direct effects on the enzymatic or regulatory properties of the DXS protein. Similarly, association of genetic variants with the content of several volatile aromatic compounds were tested for candidate genes in the mQTL interval on chromosome 10. These findings may pave the way for metabolic engineering of terpenoid contents in grapevine