Control of postharvest grey spot rot of loquat fruit with Metschnikowia pulcherrima E1 and potential mechanisms of action

Abstract

In the present study, the biocontrol efficacy of Metschnikowia pulcherrima E1 against grey spot rot (Pestalotiopsis vismiae) on loquat fruits was assessed and along with potential mechanisms of action. Results indicated that decay incidence and lesion diameter were both significantly reduced by treatment of fruits with the yeast, M. pulcherrima E1. M. pulcherrima E1 quickly colonized wounds in loquat fruit stored at either 20 °C or 4 °C. Scanning electron microscopy revealed that the yeast formed a biofilm on the wound surface in loquat fruit which inhibited the invasion of pathogenic fungi. M. pulcherrima E1 also competed with the pathogen for nutrients (iron) and space. Results of dual-culture petri dish assay indicated that M. pulcherrima E1 produces volatile antifungal compounds that inhibit the growth of P. vismiae. SPME-GC–MS analysis revealed that 3-methyl-1-butanol, phenylethyl alcohol and 1-Hexanol are the main volatile organic compounds produced by M. pulcherrima E1 and that had a significant inhibitory effect on the growth of fungal mycelia. M. pulcherrima E1 induced a higher level of defense-related enzyme activity in loquat fruit, including polyphenol oxidase, peroxidase, catalase, ascorbate peroxidase, and phenylalanine ammonia-lyase. Collectively, the results of the present study indicate that M. pulcherrima E1 has good potential to be used as a biocontrol agent against postharvest grey spot rot on loquats. The different mechanisms of action exhibited by M. pulcherrima E1 enhances its ability to control P. vismiae.