The Inhibition And Mechanism On Growth Of Fusarium Sulphureum Caused Fusarium Rot Of Muskmelon

Fusarium rot of muskmelon caused by Fusarium sulphureum is the main postharvest disease,which significantly causes the quality deterioration of muskmelon fruits and accumulates a large amount of mycotoxin,in which the accumulation of NEO,one of the trichothecenes,is most significant.Previous studies found that ozone treatment significantly inhibited the postharvest disease of fruits and vegetables by inhibiting the growth of pathogenic fungus,however,the inhibition effect on growth of F.sulphureum and the potential mechanism has not been reported.In this study,muskmelons fruits（Cucumis melon L.cv.Agate）and F.sulphureum were chosen as materials,pathogen of F.sulphureum was treated by ozone gas,then the effects of ozone treatment on development of disease diameter and the accumulation of NEO of muskmelon inoculated with F.sulphureum were determined,the effects of ozone treatment on growth of F.sulphureum spores and the cell membrane integrity were analyzed,the effect of ozone treatment on ROS metabolism and other metabolism pathways were verified by transcriptomics and RT-q PCR.The results were following:1.The development of disease diameter of the muskmelon inoculated with F.sulphureum was significantly inhibited after ozone treatment,the disease diameter after ozone treatment was significantly lower than that in control,and the accumulation of NEO in the muskmelon fruits inoculated with F.sulphureum was also significantly lower than that in control.2.The growth of F.sulphureum was significantly inhibited after 2 mg/L ozone treatment,and the spore germination,sporulation and the mycelial biomass were reduced significantly after ozone treatment.The cell membrane integrity of F.sulphureum spores was destroyed after ozone treatment,the relative conductivity,MDA content and the leakage of protein and nucleic acid were significantly increased compared with the control;the observations of SEM and TEM showed that the spores after ozone treatment were obviously shrunken and broken,and the surface was rough,organelles were markedly damaged,organelle contents was loss.3.The content of ROS（O₂^-H₂O₂）in F.sulphureum spores was significantly increased after ozone treatment,the enzymatic activities related to ROS metabolism:the activities of NOX,CAT and POD were increased,while the activities of SOD,APX and GR were inhibited.4.After ozone treatment,the differential expressed genes of F.sulphureum spores were mainly enriched in the processes of sugar metabolism,amino acid metabolism,lipid metabolism,energy metabolism and ROS metabolism.RT-q PCR results revealed that the genes involved in ROS metabolism were significantly up-regulated,while the genes related to sugar metabolism,amino acid metabolism and oxidative phosphorylation were significantly down-regulated.In summary,ozone treatment inhibited the spore germination,sporulation and growth of mycelium,and destroyed the cell membrane integrity of F.sulphureum,promoted the accumulation of ROS,enhanced the enzymatic activities and genes expression of ROS metabolism,reduced the enzymatic activities of ROS metabolism scavenger enzymes,therefore inhibiting the development of fusrarium rot and the accumulation of NEO in muskmelon fruits inoculated with F.sulphureum.