Study On Biocontrol Of Postharvest Blue Mold Decay Of Pears By Meyerozyma Guilliermondii And It's Mechanisms

Pear fruits are vulnerable to pathogen infection resulting in decay during storage,transportation and sale,which caused huge economic losses.Penicillium expansum is one of the major pathogens that causes postharvest decay of pear,which secretes the secondary metabolite patulin(PAT),causing serious food safety problems and harming human health.At present,the main methods of controlling postharvest diseases are chemical and physical methods.However,both methods have some drawbacks.Therefore,safe and efficient antagonistic yeast has been a research hotspot in the academic field to control postharvest diseases of pear.In this study,Meyerozyma guilliermondii a new antagonistic yeast was investigated to determine its ability to inhibit postharvest diseases of pear(Pyrus pyrifolia Nakai.‘‘Shuijing'').The physiological and molecular mechanisms of pear resistance and its molecular mechanism of inhibiting the growth of mold were explored.Based on this,the mechanism of antagonistic yeast against postharvest diseases of pear was explored.The main results of this paper are as follows:1.Four strains of yeasts were isolated from the surface of pear in an orchard,namely Y1(M.guilliermondii),Y2(Pseudozyma aphidis),Y3(Meyerozyma caribbica)and Y4(Bulleromyces albus),and tested in pear to control blue mold decay.They revealed that Y1(M.guilliermondii)was the best in terms of biocontrol efficacy.Acute toxicity test in mice proved that M.guilliermondii is safe and nontoxic.2.M.guilliermondii significantly inhibited the blue mold decay caused by P.expansum without affecting the quality of the pear.The increase in the biocontrol efficacy increased with increasing yeast concentrations.M.guilliermondii rapidly colonized the wounds and surfaces of the pears at both 4? and 20? and maintained relatively higher in numbers to compete for nutrition and space with pathogen and played an important role in controlling blue mold decay of pear..3.M.guilliermondii enhanced the activities of defense-related enzymes and corresponding genes.4.The total proteins and genomic information of pears in response to the induction of M.guilliermondii were analyzed and compared by proteomics and transcriptomics.The results showed that M.guilliermondii could induce the expression of defenserelated proteins and genes in pear.Defense-related proteins and genes have a corresponding relationship,such as ATP synthase and its genes,PR family of antisensitive proteins and its genes and defense-related cell wall protein and its genes were significantly up-regulated,revealing the resistance mechanism of the antagonist yeast in pear from the molecular level preliminary.5.The total proteins and genomic information of mold in response to the inhibition of M.guilliermondii were analyzed and compared by proteomics and transcriptomics.The results showed that M.guilliermondii could inhibit the expression of basal metabolism and response regulation proteins and genes in mold.Differentially expressed proteins and genes have a corresponding relationship such as: heat shock protein and its genes,phosphatase and its genes,ATP synthase and its genes and polyketide synthase and its genes were significantly down-regulated,revealing the mechanism by which the antagonistic yeast inhibited the growth of mold at the molecular level preliminary.