Study On The Inhibition Mechanism And Biocontrol Of Yeast On Anthracnose Of Postharvest Banana

Banana（Musa nana Lour）is one of the important tropical and subtropical fruits.Banana fruit is sweet and nutritious,which is popular with people.Bananas are susceptible to pathogenic fungi after harvest and lead to quality deterioration,which restricts the transportation and sales of banana fruits.Banana anthracnose caused by Colletotrichum musae is one of the main diseases of banana harvest.In this study,a strain that can effectively inhibit C.musae and has high safety was obtained.The fungistatic mechanism of this biocontrol yeast on C.musae and the effect of this biocontrol yeast on oxidative stress,active oxygen scavenging ability and disease resistance in banana fruit was studied.The results were as follows:1.A biocontrol yeast MA from mango fruit was obtained through in vitro screening and vivo screening which could effectively inhibit C.musae.Through the tests of morphological,physiological characteristics and molecular identification,it was identified as Saturnispora diversa.In addition the strain of MA was identified as a non-toxic yeast throught acute oral toxicity test in mice.2.In vitro experiments found that the suspension of S.diversa MA at the concentration of 10⁷cells/m L had a strong antifungal effect on C.musae.C.musae could not be inhibited by volatile organic compounds produced by S.diversa MA.But C.musae mycelia and spores are adsorbed by S.diversa MA,thereby inhibiting the growth of C.musae mycelia and spores germination.In addition,Fusarium sp.,Colletotrichum gloeosporioides,Colletotrichum acutatum,and Alternaria sp.also were inhibited by S.diversa MA.3.The storage period of banana fruit after inoculation with C.musae was prolonged,the ripening of banana fruit was delayed,the fruit rot rate,disease index and weight loss rate were reduced,the firmness of the banana is maintained,and the increase in total soluble solids is retarded by S.diversa MA.4.S.diversa MA could affect the reactive oxygen species metabolism system and induced disease resistance in banana fruits.The rate of superoxide anion O₂^-production in banana fruits inoculated with C.musae can be reduced by S.diversa MA.The activities of active oxygen scavenging enzymes[superoxide dismutase（SOD）,catalase（CAT）]and disease resistance-related enzymes[peroxidase（POD）,phenylalanine ammonia lyase（PAL）]were enhanced by S.diversa MA.The membrane permeability and malondialdehyde（MDA）content of banana fruits were reduced by S.diversa MA.In a certain period of time,higher endogenous antioxidants such as glutathione（GSH）and ascorbic acid（As A）in banana fruits can be maintained by S.diversa MA.However,it was found thatβ-1,3-glucanase（GLU）activity was induced to increase by S.diversa MA only in the first 4 days after storage,it was not found to effectively increase the activity of ascorbate peroxidase（APX）.5.Transcriptomics analysis revealed that disease resistance-related genes expression in banana fruits after inoculation with C.musae were significantly up-regulated by S.diversa MA.According to KEGG pathway analysis,some resistance-related pathways are affected by these genes.S.diversa MA may improve disease resistance of fruits through these pathways.The transcriptome results revealed the molecular mechanism of S.diversa MA induced disease resistance in banana fruits.