Selection and identification of potential bacteria against postharvest fungal pathogens on strawberry fruit

Strawberries are economically important owing to their unique flavour, health benefits, and nutritional aspects. Decay after harvest is a major issue in the development of strawberry industry. Currently, the most effective method for controlling decay after harvest is storage of strawberries at low temperature combined with usage of chemical fungicides. However, long-term usage of chemical fungicides not only causes pathogen resistance but also is harmful for human health and environment. Biocontrol method for the management of disease after strawberry harvest has great practical significance. In this study, totally 200 bacterial strains isolated from the surface of healthy strawberry fruit were tested for antagonistic activity against five fungal pathogens. Among them, VK199 strain was potent against all five postharvest spoilage fungi on strawberry fruit and then utilized for further study. This strain was identified as Bacillus siamensis based on sequence analysis of 16S rDNA. The extracellular lytic enzymes, including cellulase, amylase, protease and chitinase released by B. siamensis VK199 were detected. Furthemore, in vivo, the results of biological control efficacy test showed that B. siamensis VK199 suppressed the occurrence of diseases caused by Botrytis cinerea, Colletotrichum gloeosporioides, Mucor nidicola and Rhizopus delemar of strawberry during storage.