Effects Of Methyl Jasmonate On The Biocontrol Activity Of Meyerozyma Guilliermondii Against Blue Mold Decay Of Apples And The Possible Mechanisms Involved

Apple that is with extremely high nutritional value and rich in minerals and vitamins is one of the most produced fruits in the world.However,during storage and transportation after harvest,the rot that is affected by the infection of pathogenic bacteria of apples is severe,which reduced their commercial value and caused serious economic losses.Apple rot caused by pathogens mainly included Penicillium expansum(P.expansum)and Botrytis cinerea(B.cinerea),which are prone to cause apple blue mold and gray mold.Once the apple is infected by the pathogenic bacteria,the pathogenic bacteria would invade the fruit tissue through the wound quickly,that accelerated the decay of the apple.Among them,P.expansum caused the most serious damage to apples,and it produced the secondary metabolite penicillin(PAT),would harmed human health seriously.At present,the methods for controlling post-harvest fruit diseases are physical methods,chemical methods and biological methods.However,physical methods required large-scale equipment,and chemical methods have greater environmental pollution,they are not be universally applied.The biocontrol method is safe and effective,which mainly included biocontrol bacteria and antagonistic yeast.However,the biocontrol effect of antagonistic yeast is relatively poor than chemical fungicides,so how to improve the biocontrol efficacy of antagonistic yeast is an urgent problem to be solved.The use of elicitors to induce antagonistic yeast is one of the key measures to improve the biocontrol efficacy of yeast.In this paper,Meyerozyma guilliermondii(M.guilliermondii)induced by methyl jasmonate(MeJA)was used to control the blue mold of apples.We researched M.guilliermondii induced by MeJA to improve the disease resistance of apples from the physiological and molecular levels.The main research contents of the paper are as follows:1.M.guilliermondii induced by MeJA improved the effectiveness of in controlling post-harvest blue mold of apples.With the increase of M.guilliermondii concentration,the effectiveness of in controlling pathogenic bacteria is better.M.guilliermondii added 200 μmol/ L MeJA had a good control effect on the rot diameter and rot rate of apples,and also had no adverse effect on the storage quality of apples.2.Under the conditions of 20℃ and 4℃,M.guilliermondii induced by MeJA reproduced rapidly and grow on the wounds and surface of apples.In vitro experiments,MeJA increased the inhibitory effect of M.guilliermondii on the spore germination rate,germ tube length,colony diameter of P.expansum.At the same time,M.guilliermondii induced by MeJA also increased the apple-related resistance enzymes activity(PPO,POD,PAL,CAT),the content of bacteriostatic substances(flavonoids,total phenols)of apples,and increased apples’ own resistance for pathogenic bacteria.3.Through transcriptomics analysis,there were 240 differentially expressed genes was found between M.guilliermondii and M.guilliermondii induced by MeJA,included 115 significantly up-regulated genes and 125 significantly down-regulated genes.MeJA induced M.guilliermondii ascorbic acid pathway,meiosis pathway,tricarboxylic acid cycle pathway,oxidative phosphorylation pathway,energy metabolism,cell wall synthesis,ribosome growth,cell growth and other metabolic pathways,and the genes CDC39,SLK19,PGDA,ATP2,FDH1,HXT5,SSZ1,NOG2 and other related gene expression levels are increased.It indicated that MeJA improved the ability of resist oxidative stress,energy metabolism,cell wall synthesis and stability,cell growth in M.guilliermondii,thereby increased the ability of M.guilliermondii to control postharvest diseases in apples.4.Through the analysis of transcriptomics,there were 2088 differential genes was found in apples,included 1429 genes were significantly up-regulated,and 659 genes were significantly down-regulated.M.guilliermondii treated by MeJA induced apple cell wall synthesis,antioxidant stress,plant disease resistance,peroxisomes,energy metabolism,phenylpropane metabolism and other pathways.Gene expression levels of PPO,EXPA1,TFT6,GHR5,CYP73 and other genes are induced to increase,which enhanced the stability,antioxidant,stress resistance and energy metabolism of apples,and increased the content of apple flavonoids and anthocyanins.Thereby increased the self-defense of apples and the inhibition of pathogenic bacteria have prolonged the shelf life of apples.