Dynamic changes in monoterpene accumulation and biosynthesis during grape ripening in three Vitis vinifera L. cultivars.

Monoterpenes are important aroma components in grapes and wines. We analyzed the free and bound monoterpene profiles and the transcript levels of terpenoid biosynthesis genes in Vitis Vinifera cvs. Muscat Hamburg, Riesling, and Sauvignon Blanc grapes at five ripening stages. Principal component analyses revealed that the three cultivars had different free monoterpene profiles at harvest and the early stage of ripening. In all cultivars, the total bound monoterpene contents were higher than the free monoterpene contents during grape ripening. The changes in monoterpene profiles in different grape varieties were correlated with the transcript levels of some VviTPS and VviGT genes. In Riesling, the VviGT14 and VviUGT88A1L1 transcript levels were related to geraniol glucoside accumulation. In Muscat Hamburg, the VviPNLGl1, VviPNLGl2, and VviPNLGl4 transcript levels were related to linalool accumulation. Understanding the dynamic changes in monoterpene accumulation and biosynthesis will allow winemakers to devise strategies to improve grape and wine aromas.