Terpenoids, especially mono- and  sesquiterpenes, contribute to the varietal aroma of several grape varieties like Gew�rztraminer and Syrah. Recent research using stable isotope labelled precursors has shown that these compounds are constitutively biosynthesized during ripening in berry exocarp and mesocarp. While monoterpenes are generated in both parts of the berry, sesquiterpenes are predominately formed in the exocarp and enriched in the epicuticular wax layer. However, environmental cues can affect the regulation of the genes and enzymes of involved metabolic pathways leading to the modulation of the varietal aroma. In order to understand the mechanism of these responses, the influence methyl jasmonate (MeJA), which is a stress related plant hormone and an exogenous elicitor for various plant defence compounds, including mono- and sesquiterpenes, has been investigated. The in vivo effect of MeJA was studied by direct injection into grape berries. Induced volatiles were subsequently analysed in berry exo- and mesocarp by HS-SPME-GC/MS. The MeJA treatment resulted in an induction of the biosynthesis of certain mono- and sesquiterpenes only in the exocarp of grape berries. This effect was further examined in an open field study, demonstrating that the treatment of whole grape vine plants triggers the terpene biosynthesis in grape berry exocarp, which points to a systemic reaction that alters the terpene profile. The data obtained so far indicate that especially sesquiterpene biosynthesis is likely to be associated with an interaction of the grapevine genome with its environment.

Constitutive and induced biosynthesis of volatile mono-, sesqui- and diterpenoids in grape berries

248th National Meeting (2014)

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