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

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.

The authors are grateful to the University of Lleida for a Ph.D. grant to Carlos Calvo Garrido (CCG) and for the organic production research project, to the European Union for their financial support through the INTERREG REDBIO project and to the Catalan government for the travel grant to CCG. They are also grateful to the INRA UMR-Save for welcoming CCG in 2012 to conduct all of the experiments presented in this paper by using the INRA research facilities in Bordeaux and to the Conseil Interprofessionnel du Vin de Bordeaux (CIVB) for its financial support of the project. They are indebted to UMR SAVE-Bordeaux staff: J.M. Liminana and J.M. Brustis for their technical support associated with climatic chambers and vineyard plot, respectively. Also to J. Jolivet, O. Bonnard, S. Capdevielle, J. Poidatz and L. Delbac for their valuable help with laboratory assays. The authors thank Dr. Stephen Hoyte for his valuable review of the manuscript.