Screening Of Antagonists Against Mango Postharvest Anthracnose,Action Of Mechanism And Analysis Of Bacteriostatic Metabolites

Anthracnose caused by Colletotrichum gloeosporioides is well known as one of the most destructive postharvest diseases in mango fruit.At present,it mainly controls the postharvest diseases of mango by physical and chemical means.Biological control has gradually developed and become a research hotspot.Antagonistic bacteria have attracted wide attention as the research object of biological control.In this study,an antagonistic bacterium was isolated from Mango epidermis by plate confrontation method and using C.gloeosporioides as the target pathogen.It was identified by measuring the physiological and chemical characteristics combining molecular means to identify.The culture medium recipe was optimized.The antagonistic mechanisms of fermentation liquids of F1 strains for C.gloeosporioides were studied.Using GC-MS and UPLC-Q-TOF-MS techniques combined with principal component analysis(PCA)and orthogonal partial least squares-discrimination analysis(OPLS-DA)and other statistical methods to analysis of volatile gases and metabolites in fermentation broth of F1 strain.The results are as follows:(1)An antagonistic bacterium F1 was screened from mango epidermis,which had a good inhibitory effect on Mango Anthracnose fungus.And has a broad spectrum of inhibition of a variety of plant pathogens.It was identified as Bacillus amyloliquejaciens.(2)Through fermentation optimization,2%glucose,3%compound nitrogen 1(yeast extract:peptone=1:1)and 0.5%MgSO4 were selected as the medium combination.The fermentation conditions were as follows:the pH of medium is 7,th culture temperature is 28 C,the culture time is 48 h.After optimization,the inhibition rate of fermentation broth to anthrax was 80.33%,compared with the before optimization,it is increase of 24.39%.Mango was treated by optimized fermentation broth,the incidence index of the treatment group was significantly lower than the incidence index of the control group.The control effects of natural morbidity and inoculation treatment were 70.32%and 56.10%respectively.(3)The results show that the strain Fl could affect the growth of mycelia and conidia germination of C gloeosporioides,resulting in shortening and thickening,twisting and deforming,and destroying of the plasma membrane of conidia.It can inhibit extracellular enzymes such as mycelial cellulase and pectinase,and also inhibit mycelial protein synthesis of C gloeosporioides,so as to achieve bacteriostasis.(4)Through metabolite analysis,it was found that the possible antibacterial volatiles of strain F1 were 2,3-butanediol,5-methyl-2-hexanone.5-methyl-6-methyl-2-heptanone,6-methyl-6-methyl-2-heptanone and phenol.5 kinds of metabolites which inhibited the C gloeosporioides from the antagonistic F1 fermentation broth were Methyl cinnamate,Maltol,Phloretic acid,p-Chlorophenylalanine,2-Amino-5-methoxybenzoic acid.Mango was treated with maltol,p-Chlorophenylalanine and 2-amino-5-methoxybenzoic acid at a concentration of I mg/mL.The results showed that the control effect of C gloeosporioides was over 50%,and 2-amino-5-methoxybenzoic acid was the best.The control effect of inoculation with C gloeosporioides was 60.98%and that of natural diseases was 73.35%.