Genetic analysis of loose cluster architecture in grapevine
Loose cluster architecture is a well known trait supporting Botrytis resilience by permitting a faster drying of bunches. Furthermore, a loose bunch enables a better application of fungicides into the cluster. The analysis of 150 F1 plants of the superior breeding line GF.GA-47-42 (‘Bacchus' x ‘Seyval blanc') crossed with ‘Villard blanc' segregating for compactness of the cluster was used for QTL analysis. Plenty of QTL were identified reproducibly for two years, QTLs stable over three growing seasons were identified for rachis length, peduncle length, and pedicel length. In a second approach ‘Pinot noir' clones showing variation for cluster architecture were analyzed for differential gene expression. Grown in three different German viticultural areas, loose versus compact clustered ‘Pinot noir' clones showed in gene expression experiments a candidate gene expressed fivefold higher in loosely clustered clones between stages BBCH57 and BBCH71.