Abstract
Final berry mass, which is a major quality factor in wine production, is the result of the integrated effect of biotic and abiotic factors that can influence also the berry composition. Under field conditions, the interactions between these factors make the study of the variability of berry mass and composition difficult. Depending on the observation scale, the hierarchy of the impact degree of these factors can vary. The present work was designed to study the simultaneous effect of the major factors influencing berry mass and composition in order to create a hierarchy according to their impact degree. A second objective was to separate the possible direct effect of factors on berry composition from an indirect effect mediated through their impact on berry mass. Vine water and nitrogen status of six blocks, located on a sandy and a gravelly soil, were monitored during two following years. Berries from Cabernet franc were analyzed from veraison to harvest. At each sampling date, fresh berry mass, berry seed mass and number, sugar content and concentration and malic concentration were recorded. All studied factors significantly impacted the final berry mass, but vine water status represented the most impacting factor. The interaction between factors sometimes seemed to hide the significant effect of some of them on berry compounds. Nevertheless, we showed by means of appropriate statistics that all factors had a direct impact on berry sugar and malic concentration, although their order of impact varied according to the metabolites considered. Conversely, the effect of factors significantly impacting berry sugar content is mediated through their impact on fresh berry mass.
- Received September 2016.
- Revision received February 2017.
- Revision received July 2017.
- Revision received October 2017.
- Accepted October 2017.
- Published online October 2017
- ©2017 by the American Society for Enology and Viticulture
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