Study On The Effect Of Meyerozyma Guilliermondii Combined With Alginate Oligosaccharide Against Postharvest Blue Decayof Pears And The Possible Mechanisms Involved

The blue mold caused by Penicillium expansum is one of the main fungal diseases of pears after harvest,which poses a great threat to the production and marketing of pears.Antagonistic yeasts are widely used in biological control,chemical compounds can be combined with them to further improve the biocontrol effect.Therefore,the paper studied the inhibitory effect of Meyerozyma guilliermondii combined with AOS on blue mold of pears and the effect on natural storage quality of pear,explored the mechanism of action from the physiological and molecular mechanisms.Results of this study were as follows:(1)The combined use of AOS and M.guilliermondii in pears effectively reduced the incidence of blue mold,and the concentration of 5 g/L was the best.The results of natural storage experiment showed that M.guilliermondii combined with AOS can significantly reduce the natural decay rate of pears and had no adverse effects on many quality indexes of pears.(2)The physiological mechanism of the combined use of AOS and M.guilliermondii to inhibit the postharvest blue mold of pear fruits mainly included:AOS can sightly exhibit the growth of P.expansum in vitro.The combined use of AOS and M.guilliermondii on pears significantly reduced the incidence of blue mold,increased the activity of resistance-related enzymes and the relative expression of genes.The content of total phenols and flavonoids were improved and the content of MDA was reduced to weaken membrane lipid peroxidation.(3)Through transcriptome analysis,it was found that M.guilliermondii can induce the resistance of pears mainly from promoting signal transduction,inducing up-regulation of several disease-resistance genes and defense genes,improving the ability of antioxidant stress,promoting the synthesis of resistant substances,maintaining the integrity of cell membrane and cell wall strength and increasing the expression of enzymes closely related to resistance.M.guilliermondii combined with AOS can further improve the resistance of pears by promoting the synthesis of resistant substances,inducing the up-regulation of resistance related genes,promoting signal transduction,regulating the expression of enzymes closely related to resistance and maintaining the strength of cell wall.(4)The treatment of M.guilliermondii can increase resistance of pears mainly by affecting purine metabolism,amino acid biosynthesis,zeatin biosynthesis and flavonoid biosynthesis pathways,as well as improving the content of substances associated with resistance such as phenylpropanoids,flavonoids,terpenes,some organic acids and so on.AOS can be used in combination with M.guilliermondii to improve the resistance of pears by influencing the biosynthetic pathway of flavonoids,promoting the accumulation of flavonoids,cinnamic acid derivatives,triterpenoids and some phenols.