UC Davis

From its center of domestication in the forests of the Caucasus to vineyards on every inhabited continent, the grapevine, Vitis vinifera subsp. vinifera, has been valued for the organoleptic properties of its fruit and wine. Among these properties, aroma has been especially important, inspiring extensive cultural, agricultural, and scientific interest. Wine aroma arises from a complex mixture of volatile compounds that may originate in the grape itself, be released from non-volatile precursors during fermentation and aging, or be introduced through winemaking practices and environmental sources. Considerable research has examined the chemical composition of grapes and wine, the volatile products of yeast and bacterial fermentation, the contribution of oak-derived compounds, and the transformations that occur during wine aging. Only recently, however, have researchers begun to investigate the genetic basis of aroma compound biosynthesis and metabolism.This dissertation examines the genetic basis of grape aroma variation and its translation into wine aroma with an emphasis on monoterpenes. Chapter 1 reviews the current understanding of genes and pathways involved in grape and wine aroma, focusing on major volatile compound classes including monoterpenes, sesquiterpenes, norisoprenoids, methoxypyrazines, furan derivatives, volatile sulfur compounds, lipoxygenase pathway products, and phenylpropanoid-derived compounds. By compiling functionally characterized aroma-related genes and placing them in the context of grapevine genome resources, we identify both the progress made in aroma genetics and the remaining gaps in linking genetic variation to aroma biosynthesis and metabolism.