Biocontrol strategies in the management of Cadophora luteo-olivacea, skin-pitting agent of kiwifruit

Skin-pitting disease causes great economic losses on kiwifruit (Actinidia deliciosa (A. Chev.) C.F. Liang & A.R. Ferguson) production, as the symptoms appear on fruits only after 3-4 months of cold storage. Nowadays, very few synthetic active compounds are allowed during the postharvest period, because of the related residues’ problem. For this reason, the goal of the present study was to search for alternative strategies to control skin-pitting. Thus, the efficacy of bacteria and yeasts strains as biocontrol agents (BCAs) was tested by in vitro and in vivo assays against Cadophora luteo-olivacea strains, the causal agent of skin-pitting disease of kiwifruit. The efficacy of different BCAs (Bacillus, Pseudomonas, Metschnikowia, and Aureobasidium spp.) belonging to our laboratory collection, purchased, and derived compounds from a commercial bio-fungicide, was tested by in vitro assays against the fungal mycelial growth. In vitro results showed that the strains Pseudomonas synxantha 117-2b and Bacillus amyloliquefaciens FZB24 were the most effective against the pathogen growth through the tested antagonistic strategies. Strains P. synxantha 117-2b and B. amyloliquefaciens FZB24, as the most active BCAs by in vitro experiments, were also tested on kiwifruit. From preliminary results, the antagonists appeared promising in reducing the incidence of skin-pitting symptoms by 73 and 60%, respectively, so, proposing a valid and sustainable alternative strategy to control C. luteo-olivacea during the storage.