Biological control of Botrytis bunch rot in Atlantic climate vineyards with Candida sake CPA-1 and its survival under limiting conditions of temperature and humidity

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English. Candida sake CPA-1 is an antagonistic yeast that has previously been shown to effectively control Botrytis bunch rot in grapes. The efficacy of biological control agents is dependent on their survival, which may also depend on climatic conditions. However, few studies have evaluated the effect of abiotic factors affecting the survival of biological control agents, such as temperature (T) or relative humidity (RH). In this study, efficacy of C. sake (5 × 107 CFU mL−1), which was applied with the additive Fungicover (FC; 50 g L−1), was tested against BBR in the laboratory and in field trials under the Atlantic climate conditions of the Bordeaux region (France). The study also evaluated the survival of C. sake under T and RH regimes simulated in climatic chambers. Two or five applications of C. sake plus FC during the growing season significantly reduced BBR severity at harvest by 48% and 82%, respectively, when compared to the control. Similar reductions were achieved after inoculation with selected virulent Botrytis cinerea strains (75% compared to control) in laboratory experiments. C. sake populations showed minimal decreases between field applications and were favored by simulated Atlantic climate conditions. The survival pattern of C. sake exposed to 40 and 45 °C combined with 30% and 100% of RH was described, demonstrating a sharp decrease during the first 24 h. Allowing 48 h for C. sake to incubate and become established on fruits prior to the exposure to 40 °C and 30% RH increased survival (P < 0.05). These results confirm the efficacy of treatment with C. sake plus FC under favorable climatic conditions for BBR development, while survival studies may help to improve the survival and efficacy of yeast BCAs, such as C. sake CPA-1.