Inhibiting Effect Of CB-M Antimicrobial Peptide On The Gray Mold In Postharvest Fruits And Mechanisms Involved

Gray mold,caused by Botrytis cinerea,is a common postharvest disease and can easily cause fruit decay and reduce fruit storage quality.For a long time,chemical fungicides remained the main way to control the postharvest decay in fruits and vegetables.However,excessive use of chemical fungicides was harmful to the environment,food security as well as human health.Compared with chemical fungicides,antimicrobial peptides(AMPs)have small molecular weight,easy degradation,and broad-spectrum antibacterial activity.In addition,AMPs also have some advantages including good thermal stability,low level of drug resistant,short duration of action on microorganisms,and low toxicity to cells.AMPs are expected to be a good substitute for fungicides and have broad application prospect in controlling postharvest diseases of horticultural plants.In this study,the antifungal activity of CB-M antimicrobial peptide against two kinds of B.cinerea(Bc1 and Bc2)in vitro were studied.Results showed that CB-M antimicrobial peptide had strong inhibition effect on the growth and killing effect on the spores of both B.cinerea,and these effects increased with the increase of CB-M concentration.The minimum inhibitory concentrations of CB-M against B.cinerea Bc1 and Bc2 were 4 μg/m L and 2 μg/m L,respectively.Secondly,the in vitro inhibition mechanism of CB-M antimicrobial peptide on B.cinerea was studied by the determination of cell membrane integrity,cell ultrastructure observation,DNA binding ability,protein synthesis analysis,and the release of cytoplasmic constituents.Results showed that the mechanism of action of CB-M antimicrobial peptide on B.cinerea is the damage of membrane integrity and mycelial morphology,the leakage of nucleic acid,carbohydrate and other substances,the degrade or inhibit the synthesis of proteins,and binding with genomic DNA leading to cell death.Finally,CB-M antimicrobial peptide was applied to three kinds of postharvest fruits(tomato,cherry tomato,grape),and it was found that the CB-M significantly inhibited the disease incidence and lesion diameter of gray mold in these fruits during storage.In order to explore the ability of CB-M antibacterial peptide on inducing the resistance against gray mold in fruits,cherry tomato was used as experimental material and the activities of antioxidant related enzymes and disease resistance-related enzymes,and the contents of pathogen resistance-related substances and pathogenesis-related proteins(PRs)during storage after CB-M treatment was determined to clarify the effect of CB-M antimicrobial peptide on the gray mold in postharvest fruits and mechanisms involved.Results showed that the disease incidence of gray mold caused by B.cinerea Bc1 on cherry tomatoes,grapes,and tomatoes in the CB-M treatment group was 9,19,and 19-times lower than that in the control group on last day,respectively.The disease incidence of gray mold caused by B.cinerea Bc2 on cherry tomatoes in the CB-M-treated group was 2.3-times lower than that in the control group on last day.Meanwhile,CB-M treatment increased the activities of superoxide dismutase,peroxidase,and catalase,accelerated the accumulation of pathogen resistance-related substances and PRs,and promoted the increase in the activities of several disease resistance-related enzymes,including chitinase,β-1,3-glucanase,and phenylalanine ammonia-lyase during the storage.In conclusion,CB-M antimicrobial peptide had a significant antibacterial effect on B.cinerea in vitro.Furthermore,CB-M antimicrobial peptide could destroy the cell membrane leading to the leakage of nucleic acid,carbohydrate and other substances,and destroy the morphology of B.cinerea mycelium.In addition,it can prevent and control the development of gray mold in tomato,grape,and cherry tomato,and induce the resistance of cherry tomato against gray mold in vivo.This antimicrobial peptide is expected to be a new broad-spectrum antibacterial agent,which can provide more comprehensive information for the application and mode of action of antimicrobial peptides,and provide an effective strategy for controlling postharvest diseases of fruits and vegetables.