Inhibitory Effect And Molecular Mechanism Of Chitosan On Postharvest Botrytis Cinerea And Penicillium Expansum Of Cherry Tomato

Post-harvest diseases lead to the spoilage of fruit and vegetable.Botrytis cinerea and Penicillium expansum are major fungal disease causing post-harvest diseases.Chitosan is widely used in post-harvest preservation and disease control of fruit and vegetable because of its good film-forming and antibacterial properties.In this research,the inhibitory effects and possible mechanism of chitosan on the Botrytis cinerea and Penicillium expansum growth were studied.In addition to this,the effect of chitosan on the storage quality of cherry tomato was investigated.In vitro,it was to examine the inhibitory effects of chitosan with four different concentrations against Botrytis cinerea and Penicillium expansum spore germination,mycelial growth,and Penicillium expansum colony extension.In vivo,we studied the effect of chitosan on Botrytis cinerea and Penicillium expansum diseases of cherry tomato.Meanwhile,cherry tomatoes were stored after the chitosan solution soaked,and the effects of chitosan on the storage quality were measured by detecting four quality indexes of weight loss rate,firmness,soluble solids and reducing sugar content.In addition,the content of reactive oxygen species(ROS),malondialdehyde(MDA),peroxidase(POD)were detected in cherry tomato fruits after the chitosan solution soaked.The expression level of disease-resistant related genes in the pericarp of cherry tomatoes was detected by qRT-PCR.We expect to study molecular mechanism of chitosan inhibiting post-harvest diseases.The results showed that chitosan had obvious inhibitory effect on the spore germination and mycelia growth of Botrytis cinerea and Penicillium expansum,and the inhibitory effect was relative to concentration of chitosan,but not related on colony extension of Penicillium expansum.0.2 % chitosan has obvious inhibitory effect.The disease incidence and lesion diameter of cherry tomato inoculated by Botrytis cinerea and Penicillium expansum spore suspension after soaked with 0.2 % chitosan solution was significantly lower than control.The effects of chitosan on the storage quality of cherry tomato soaked with 0.2 % chitosan solution,including the soluble solids,reducing sugar content,weight loss rate and firmness,were better than the control group.The results showed that chitosan had a positive effect on improving the disease resistance and storage quality of cherry tomato.After soaking with 0.2 % chitosan solution,the accumulation of reactive oxygen species in cherry tomato peel was observed at 10 min,and gradually decreased after 1 h.Meanwhile the expression levelof MPK3,MPK6 and PR1a1 were significantly enhanced at 10 min after 0.2 % chitosan solution soaking,while PR5 was significantly enhanced at 20 min.The MDA content of cherry tomato soaked with 0.2 % chitosan solution was lower than the control group at the 5th day.POD activity of the treatment group was significantly higher than the control group at the 3th and 5th days.These results suggested that chitosan might control post-harvest fungal disease of cherry tomato through activating MAPK cascade pathways and enhancing the resistance to pathogenic fungus.