Evaluation Of Viticultural Impacts On 3-Isobutyl-2-Methoxypyrazine Concentrations In Vitis Vinifera L. Cv. Cabernet Franc
Studies were conducted in New York State to identify the major environmental and viticultural factors that influence 3-isobutyl-2-methoxypyrazine (IBMP) evolution in grapes and to develop management strategies to control IBMP levels. Partial least squares regression was used to model the concentration of IBMP in berries at 50 days after anthesis (DAA, accumulation) and log-fold decrease in IBMP concentration from 50 DAA to harvest (degradation) as a function o f viticultural and environmental data collected from multiple Cabernet franc vineyards (10 in 2008 and 8 in 2009). The most important predictors for modeling IBMP accumulation were factors associated with vine vigor, and higher vigor was positively correlated with IBMP accumulation. IBMP degradation could not be satisfactorily modeled across multiple sites, but within sites, factors associated with vine vigor, crop to vine size, and fruit maturity were important predictors. In the warmer growing season (2008), IBMP concentrations at 50 DAA (range 2008 = 103 to 239 pg/g; range 2009 = 12 to 87 pg/g) were significantly higher than 2009 at all 8 sites. IBMP degradation was less in the cooler growing season, but harvest concentrations (range 2008 = 1 to 13 pg/g; range 2009 5 to 14 pg/g) were not significantly different between years at 5 out of 8 sites as a result of lower preveraison accumulation. Basal leaf removal treatments imposed preveraison reduced IBMP concentrations in Cabernet franc (34 to 88%) and Merlo t (38 to 52%) berries at harvest, but postveraison treatments were not efficacious. Shoot tipping and chlormequat treatments applied to Cabernet franc vines during the preveraison period altered vine growth and canopy density, but did not affect IBMP concentrations in berries at harvest. Clonal selection was evaluated as a potential tool to manage IBMP, but the Cabernet franc clones under study (1, 214, 312, 327) did not possess distinct characteristics that consistently resulted in differential vine growth and IBMP concentrations. These experiments suggest that high IBMP concentrations are likely to occur in vigorous sites where high preveraison temperatures are followed by poor ripening conditions. Preveraison basal leaf removal and managing for vine ba lance are potential strategies to control IBMP levels.
methoxypyrazines; 3-isobutyl-2-methoxypyrazine; ibmp
Vanden Heuvel, Justine E.
Ph. D., Horticultural Biology
Doctor of Philosophy
dissertation or thesis