Early evaluation of grape berry susceptibility to Botrytis cinerea under contrasting growing conditions

Abstract

Substantial economic losses occur in grapevines due to Botrytis Bunch Rot (BBR). The control of this disease is still largely based on periodic anti-Botrytis specific fungicide spraying. Therefore, protection strategies must be optimized in order to reduce pesticide applications. Our main objective was to propose and evaluate disease risk indicators at early grapevine phenological stages related to the potential susceptibility of berries to BBR. The relationships between grapevine fruit features, i.e. pectin and tannin content in berry skins measured at berry pea-size stage, and BBR intensity at harvest were investigated. Between 2010 and 2016, an experimental field with Merlot cultivar located in the Aquitaine Region (France) and another with Merlot and Sauvignon Blanc cvs. in the Maule Region (Chile) were studied. Analyses of pectin and tannin compounds were performed to characterize berry susceptibility to BBR, and both the incidence and severity of the disease were evaluated at harvest. Furthermore, a Potential Berry Susceptibility (PBS) index was calculated using pectin and tannin concentrations. The results showed positive and linear relationships between BBR intensity with pectins and PBS index, whereas negative and linear relationships occurred between BBR intensity and tannin concentrations. All these relationships were statistically significant, except for the correlation between pectins and BBR incidence. This work points out key disease risk indicators, which could be useful for the decision making of fungicide applications against BBR.