Effects Of Ozone Treatment On Postharvest Fusarium Infection Of Muskmelon

Melon is a kind of climacteric fruit with a unique network structure peel.It is easy to be invaded by pathogenic bacteria in the process of post-harvest storage and transportation,which leads to fruit decay and deterioration,and loss of commercial value.Our previous research found that ozone,as a green fresh-keeping method,is beneficial to inhibiting the infection of Fusarium spp.and maintaining the storage quality in postharvest melons,but its appropriate concentration and mechanism are not clear.In this paper,different concentrations of ozone were used to treat isolated fusarium oxysporum and melon infected by fusarium oxysporum.The appropriate ozone concentration was determined by measuring the lesion diameter and melon storage quality,and the effect of ozone treatment on the metabolism of Fusarium-infected melon cell wall was further explored.The results showed that:(1)Ozone treatment can effectively inhibit Fusarium infection in vitro,and the ozone treatment threshold of postharvest melon infected by Fusarium is 149.8 mg/m~3.(2)Ozone treatment was beneficial to maintain the postharvest storage quality of fusarium infected muskmelon.The soluble solid content and the MDA accumulation were increased and reduced in the peel and flesh of the postharvest melon,respectively.However,the weight loss rate of postharvest melons was not sensitive to ozone.Compared with other ozone treatment groups and control groups,149.8 mg/m3 ozone treatment could make the Fusarium-infected melon at a lower level of respiration intensity and maintain higher melon peel and pulp firmness.(3)Ozone treatment affected the changes of cell wall components by regulating the activities of enzymes related to cell wall metabolism in muskmelon after Fusarium infection.Ozone treatment can inhibit the activity of Polygalacturonase,Pectin methylesterase,β-galactosidase,α-l-arabinofuranosidase,β-1,4-d-glucanase,andβ-glucosidase in the skin and pulp of melon infected by Fusarium,maintain a high content of protopectin,cellulose,and hemicellulose,low soluble pectin content and delay the softening of postharvest melon.(4)Compared with the control group,ozone treatment could inhibit the expression of PG1,PG3,GAL1,GAL2,ALF,and GLU1 genes in pericarp in the early storage period,and the expression of PG1,PME1,PME4,GAL1,ALF,Cx,and GLU1 genes in the middle storage period.and the expression of PME2,GAL1,ALF,and GLU1 genes in the later stage of storage.At the same time,ozone treatment inhibited the expression of PG3,GAL1,Cx,and GLU1 genes in the pulp at the early stage of storage,the expression of PG3,ALF,and Cx genes in the middle stage of storage,and the expression of PG1,PME2,PME3,PME4,GAL2,and Cx genes at the end of storage.The expression regulation of cell wall metabolism-related genes in postharvest melons infected with Fusarium by ozone treatment changed dynamically depending on the location of the fruit and the storage time.In conclusion,ozone treatment can inhibit the growth of Fusarium oxysporum and delay the infection process of Fusarium oxysporum on postharvest melon.Ozone treatment could inhibit the enzyme activity and gene expression related to cell wall metabolism to regulate the accumulation pattern of cell wall components,maintain higher cell wall components,delay softening,and maintain the postharvest storage quality of fusarium infected melon.