Biocontrol ability and action mechanism of Bacillus halotolerans against Botrytis cinerea causing grey mould in postharvest strawberry fruit

Abstract

Bacillus species are promising agent for the biological control of postharvest diseases. This study investigated the bio-control efficiency of Bacillus halotolerans KLBC XJ-5 against grey mould caused by Botrytis cinerea in postharvest strawberries, together with its underlying antagonistic mechanism. Treatment with B. halotolerans KLBC XJ-5 controlled mycelial growth as well as conidial germination of B. cinerea in vitro. The grey mould in strawberries inoculated with B. halotolerans KLBC XJ-5 was lower in comparison with that in the control fruit after 4 d of incubation. Genome sequencing and further bioinformatic analyses suggested that strain KLBC XJ-5 harboured six antimicrobial biosynthesis gene clusters, besides four glycoside hydrolase family 18 gene clusters involved in chitin degradation. In addition, it secreted the lytic enzyme chitinase (CHI). B. halotolerans KLBC XJ-5-treated strawberries exhibited significant induced enzyme activities (polyphenol oxidase, phenylalanine ammonia lyase, β-1, 3-glucanase, and chitinase) and compounds related to disease resistance (total phenols, flavonoids). Compared to the control fruit, B. halotolerans KLBC XJ-5-treated fruit did not present differences on nutritional quality (measured in ascorbic acid, titratable acidity, and total soluble solids). Thus, it can be concluded that B. halotolerans KLBC XJ-5 could be potentially useful as a suitable bio-control agent in harvested strawberries.