| Postharvest diseases of apple fruits during storage due fungal infection,lead to serious economic losses.Moreover,patulin which is one of the main mycotoxins produced by Penicillium expansum threaten the health of eaters.The main method of controlling postharvest diseases of fruits is the application of chemical fungicides.However,frequent application of chemical fungicides have led to resistance of pathogens.Furthermore,the continuous use of chemicals has led to the pollution of the environment and most chemical treated foods pose residual effects on human.Therefore,it is essential to develop new methods to control postharvest diseases.In recent years,biocontrol have proved to be an effective alternative measure for managing postharvest diseases of fruits and vegetables because of its safety to human life and its environmental friendliness.In this study,we used the antagonist Sporidiobolus pararoseus Y16 isolated and identified by our laboratory.The efficacy of S.pararoseus Y16 in the control of postharvest decay of apples and the possible mechanisms involved in the degradation of patulin were investigated.This study focused on following aspects:1.S.pararoseus Y16 was observed to show the best inhibitory effect of four yeasts to P.expansum in apples.Application of S.pararoseus Y16 induced defense related activities of apples against P.expansum,and decreased the decay incidence of apples.The higher the concentration of S.pararoseus Y16,the lower the disease incidence.2.The results showed that the population of S.pararoseus Y16 increased rapidly in apple wounds and outcompeted the P.expansum for space and nutrition.In vitro test indicated that germination of spores and growth of P.expansum were markedly inhibited by S.pararoseus Y16.Moreover,S.pararoseus Y16 inhibited the absorption of reducing sugars and helped degrade chitin,one of the main ingredients of cell wall in P.expansum resulting in the inhibition of energy metabolism and growth of P.expansum.In addition,S.pararoseus Y16 induced activities of defense-related enzymes such as Polyphenoloxidase(PPO),Peroxidase(POD),Catalase(CAT)and Phenylalanine ammonia lyase(PAL).It was also observed that total phenols and flavonoids of apples contents were increased.3.The relative expressions of defense-related genes such as PR-3,PR-5,PR-9,PR-4,PR-1 and genes transcriptional activator PTI5 were induced by S.pararoseus Y16,which may explain the mode of action of the genes.4.S.pararoseus Y16 could degrade patulin.The mechanism of patulin degradation was studied by S.pararoseus Y16 in vitro.The findings revealed that degradation of patulin require live yeast cells,which produced intracellular enzymes.5.The proteomics data on S.pararoseus Y16 cells in response to patulin after inoculation was analyzed in two-dimensional gel electrophoresis.The results showed that in the process of degradation of PAT,the expression of several defense-related proteins and a variety of basal metabolic proteins in yeast cells were significantly different.Heat shock protein(HSP),Fructose-bisphosphate aldolase(FBA),Mannose-1-phosphate guanylyltransferase(GDP),Fumarate reductase(NADH),Citrate synthase(CS),Ribosomal protein(RP)etc.were up-regulated during the degradation of patulin by S.pararoseus Y16. |
