A 2-year multisite study of viticultural and environmental factors affecting rotundone concentration in Duras red wine

Aim: A study was carried out in 2013 and 2014 to determine the key environmental and viticultural variables affecting the concentration of rotundone, the black pepper aroma compound, in Vitis vinifera L. cv. Duras red wines at 10 different vineyard blocks.Methods and Results: For each block, data for fruit quality attributes, as well as climatic and agronomical variables, were collected. Rotundone was quantified in wines prepared by microvinification techniques (in a 1-L Erlenmeyer flask). Rotundone concentration varied across blocks from 63 ng/L to 239 ng/L in 2013 and from 25 ng/L to 115 ng/L in 2014. Three separate partial least squares regression models were constructed to predict rotundone concentration in wines in 2013, in 2014, and in both vintages. Gluconic acid, a secondary metabolite of Botrytis cinerea, had a substantial contribution to the 2013 and multivintage models, with a negative regression coefficient with rotundone concentration. Other predictors were associated with abiotic factors such as cumulative rainfall, thermal index, hours of sunshine and mean daily irradiation.Conclusions: Our results indicate that mesoscale climatic variables are the key factors determining rotundone concentration, and also suggest that Botrytis cinerea may be involved in rotundone degradation.Significance and impact of the study: Our findings may assist grape growers producing Duras red wines to select specific vineyard blocks with the aim of producing wines with a desired rotundone concentration. They also open up new fields of investigation into mechanisms involved in possible rotundone degradation by Botrytis cinerea.