Exploring the effect of β-glucan on the biocontrol activity of Cryptococcus podzolicus against postharvest decay of apples and the possible mechanisms involved

Abstract

China is one of the largest producers of apples worldwide. Apple decay caused by Penicillium expansum has led to serious economic losses and, therefore, is a major concern. In this work, we investigated the efficacy of Cryptococcus podzolicus enhanced by β-glucan in controlling the postharvest decay of apples and the possible mechanisms involved in this process. Our results showed that β-glucan increased the biological control ability of Cryptococcus podzolicus. Additionally, the treatment did not have adverse effects on various storage quality parameters of the apples. When enhanced by β-glucan, Cryptococcus podzolicus grew better in apple wounds at either 20 °C or 4 °C. Our results also indicated that in treated apples, the activities of defense-related enzymes, including polyphenol oxidase (PPO), peroxidase (POD), phenylalanine ammonia-lyase (PAL), and catalase (CAT), increased whereas malondialdehyde (MDA) content decreased. Moreover, different proteins from Cryptococcus podzolicus were identified using two-dimensional gel electrophoresis. This analysis also showed that the expression of some proteins involved in cell wall synthesis and energy production outside of basic metabolism was upregulated when Cryptococcus podzolicus was enhanced by β-glucan. These results suggest that β-glucan treatment has a high potential for the enhancement of biological control, which could finally limit the adverse effects of Penicillium expansum.