Mode of action of a fatty acid-based natural product to control Botrytis cinerea in grapes

Aims: To investigate the efficacy and mode of action of the fatty acid-based product Foodcoat((R)) (FC) against Botrytis cinerea. Methods and Results: In vitro, in vivo and field experiments were carried out to investigate the effect of different concentrations of FC on B.cinerea germination and infection of grape leaves and berries, using three selected isolates and comparing results with those achieved by the commercialized product Protector(HML) (PRT). Furthermore, the effect of field applications of FC on the grape berry microbiota was investigated. FC reduced B.cinerea germination and grape berry severity by up to 54 and 96%, respectively, compared with the untreated controls. Conclusions: Foodcoat demonstrated efficacy that was equal or greater than the registered product, PRT. A multiple mode of action was hypothesized for FC suppression of B.cinerea, including: inhibition of germination and germ tube alteration, protection of host green tissues and enhancement of the natural yeast populations on the berry surface. Significance and Impact of the Study: The efficacy of both products has been quantified and their modes of action described, suggesting them for field applications against B.cinerea, alone or in combined strategies. This is also the first report of a fatty acid-based product stimulating natural yeast populations on grape berries.

Authors are grateful to the University of Lleida for the PhD grant to Carlos Calvo-Garrido and the Catalan Government for the overseas travel grant to encourage international research collaboration with Plant & Food Research Institute, Ruakura Research Centre, Hamilton, New Zealand. The authors also wish to thank General Manager of BioProtection, PFR, Ms Philippa Stevens for supporting this joint project and to Drs Tony Reglinski, Stephen Hoyte and Kirstin Wurms in the Biological Control and Natural Products Team of PFR for their valuable assistance. Thanks are also expressed to Dion Mundy and Victoria Raw for valuable technical support and assistance with treatment applications and sampling of research plots in Marlborough, New Zealand. We thank to Henry Manufacturing Ltd and Domca S.L. for the supply of PRT and FC, respectively.