Seminars

Grape cultivars impart organoleptic distinction, but to date we do not know the genetic determinants of wine flavor, the genes contributing to varietal differences, or how the expression of the genetic potential of grape varieties is modulated by the environment, the local microbiome, and farming practices. Phenotypic diversity in the grape germplasm reflects a substantial unshared gene content between cultivars, with 5 - 10% of the genes missing when two cultivars are compared. The structural diversity of grape genomes makes using a single one-size-fits-all reference genome inappropriate. After the release of genome of a homozygous derivative of Pinot noir (var. PN40024) in 2007, no genome reference of equivalent or greater quality has been released. This is due to the exceptionally high heterozygosity of grapevines. Wild grapes are diecious and, thus, obligate outcrossers. Although cultivated grapes are hermaphroditic, they suffer from inbreeding depression and are mostly first-generation crosses of distinct genotypes. We showed that cultivated grape accessions contained 5.2% more deleterious variants than wild individuals, and these were more often in a heterozygous state likely due to clonal propagation as suggested by forward simulations. Based on our experience with Cabernet Sauvignon, we have optimized the FALCON-unzip pipeline to assemble more efficiently and more quickly genomic contigs of grape cultivars and expanded the genome assembly to additional wine grape cultivars and wild grape species, which are being used as reference for quantitative trait mapping and genome-wide transcriptional analyses.