Screening and identification of an antagonistic yeast controlling postharvest blue mold decay of pears and the possible mechanisms involved

Postharvest disease of pears caused by pathogens results in great economic losses. The aim of this research was to isolate a strain of potential antagonistic yeast from soil of orchards, and to test the control efficacy against postharvest blue mold decay of pears. By molecular biological identification based on comparative sequence analysis of 5.8S rDNA gene, the antagonistic strain was identified as Wickerhamomyces anomalus. The results showed that W. anomalus significantly reduced the disease incidence and lesion diameter of blue mold of pears compared with the control in vivo. The disease incidence caused by Penicillium expansum of pears was only 5.56%, when treated with 1x10(8) cells/mL W. anomalus, compared with 100% disease incidence of the control. In vitro test showed that W. anomalus reduced the spore germination rate and germ tube length of P. expansum. Meanwhile, polyphenoloxidase (PPO), peroxidase (POD), catalase (CAT) and chitinase (CHI) activities of the pears treated by W. anomalus were significantly higher than that of the control. And the expression levels of defense-related enzymes were significantly induced by W. anomalus. All these results indicated that W. anomalus has the potential to control postharvest diseases of pears, and the mechanisms involved in inhibiting spore germination and germ tube length, induction of the activities of the defense-related enzymes of pears, and improvement of the expression levels of defense-related genes of pears.