The Research On Biocontrol Efficacy Of Yarrowia Lipolytica On Root Rot Of Postharvest Asparagus And The Involved Mechanisms

Root rot caused by Fusarium proliferatum is one of the main diseases of postharvest asparagus.Chemical fungicides are widely used to control diseases of postharvest asparagus.However,long-term use of chemical fungicides could produce drug-resistant strains,and the residual fungicides can do harm to consumers.Antagonistic yeasts have been widely used in the biocontrol of postharvest fruits and vegetables diseases due to its advantages of high efficiency and safety.However,there have been no reports on the control of asparagus by antagonistic yeast.In this paper,we screened antagonistic yeast with control effect on root rot of asparagus,analyzed and revealed its physiological and molecular mechanism of controlling.This study provided theoretical support and technical support for the application of antagonistic yeast in the control of postharvest asparagus disease,and had certain practical application value for the storage and preservation of asparagus.The main research results are as follows:1.Experiments in vitro and in vivo were conducted to investigate the inhibitory effect of different yeasts on F.proliferatum and the control effect of root rot in postharvest asparagus.The results showed that Yarrowia lipolytica had the best inhibitory effect on pathogen and best control effect of root rot in postharvest asparagus.This yeast can also reduce the natural decay rate and disease index of asparagus without adverse effect on its quality,and it also can reduce the deterioration of asparagus quality.2.Results showed that its physiological control mechanisms mainly included inhibiting spore germination and germ tube elongation;taking up nutrition and space on to inhibit the pathogen,increasing the activities of enzymes related to resistance including polyphenol oxidase(PPO),peroxidase(POD),catalase(CAT),superoxide dismutase(SOD)and glutathione reductase(GR);enhancing the activities of respiratory metabolism-related enzymes including pyruvate kinase(PK),fructose-6-phosphate kinase(PFK),citrate synthase(CS),mitochondrial isocitrate dehydrogenase(ICDHm),?-ketoglutarate dehydrogenase(?-KGDH),succinate dehydrogenase(SDH),6-phosphate glucose dehydrogenase(G-6-PDH)and 6-phosphate gluconate dehydrogenase(6-PGDH);and maintaining a higher energy charge and a higher reduction level.3.The effects of Y.lipolytica treatment on postharvest asparagus gene expression were studied by transcriptome technology,and the molecular mechanisms of Y.lipolytica treatment on disease of postharvest asparagus were analyzed by bioinformatics.The mechanisms mainly included:Y.lipolytica inducing the expression of genes related to cell membrane and cell wall formation of postharvary asparagus,which were conducive to maintaining the integrity and stability of cell membrane and cell wall of asparagus to resist pathogen infection;activating the expression of important genes in signal transduction pathways such as SA,ET,JA and Ca²⁺as well as their downstream defense genes,thus enhancing the disease resistance of postharvary asparagus;increasing the expression of genes related to antioxidant stress in postharvest asparagus,thus scavenging excessive reactive oxygen species(ROS),maintaining the stability of REDOX state and avoiding peroxidation damage;increasing the expression of genes involved in the synthesis of resistant substances in postharvest asparagus,increased the synthesis of lignin,flavonoids and phenols,and thus improved the resistance of asparagus;and increasing the expression of genes related to respiratory metabolism of postharvest asparagus,providing material basis and sufficient energy for physiological activities and defense response.