Microbiological Mechanism Of Selenium Combined With Methyl Jasmonate In Controlling Tomato Gray Mold

Tomato is susceptible to Botrytis cinerea in both the growth and storage periods,which seriously affects the quality and yield of tomato.Nowadays,the control of tomato gray mold is mainly based on fungicides,but the large-scale use of chemical fungicides has led to problems such as environmental pollution,ecological imbalance.Selenium is one of the beneficial elements of plants,which helps to enhance plant disease resistance.Methyl jasmonate is a plant growth regulator that can significantly induce disease resistance and improve the quality of fruits and vegetables.Plant microbial communities play an important role in the regulation of plant metabolism and immune system processes Based on the biological functions of selenium and methyl jasmonate,this study combined the two in order to obtain more effective and ecologically safe tomato gray mold disease control measures.First,the antifungal effect and mechanism of the two on Botrytis cinerea were explored in vitro.Then,the effects on tomato gray mold disease prevention and control and fruit quality were studied through pot experiments.On this basis,the microbiome characteristics of tomato fruits and leaves were analyzed,the strains with significant antagonistic effect on Botrytis cinerea were screened.Finally,the control effect of antagonistic bacteria on tomato gray mold was verified by pot inoculation experiments.The research will help to clarify the prevention and control effect of selenium and methyl jasmonate on tomato gray mold from the perspective of biological control,and provide scientific accumulation for the establishment of safe prevention and control technology.The main results are as follows:(1)Under in vitro conditions,the cell membrane permeability and malondialdehyde content of Botrytis cinerea were significantly increased by selenium treatment alone;the soluble protein content of mycelia was significantly decreased by methyl jasmonate treatment alone;the combined treatment of selenium and methyl jasmonate significantly inhibited the growth of Botrytis cinerea spore germination and hyphae growth,the secretion of oxalic acid from hyphae was 0.142 mg/m L,which was 74.59% lower than that of the control group.(2)Selenium and methyl jasmonate improved the disease resistance of tomato fruits and leaves,inhibited the infection and expansion of Botrytis cinerea,the severity of Botrytis cinerea was assessed based on the diameter of the lesions on the tomato surface:the average score of the control group was 32 points,the average scores of the soil application of 0.3 mg/kg or 2 mg/kg of selenium combined with foliar application of methyl jasmonate were 17.75 and 15.75 points,respectively.Selenium in combination with methyl jasmonate improves tomato quality.Among them,when 2 mg/kg selenium was applied to the soil and 0.2 mmol/L methyl jasmonate was applied to the foliage,the soluble protein content and vitamin C content of tomato fruit were the highest,which were increased by 43.36% and 22.15%,respectively,compared with the control group.With the increase of soil selenium application,the absorption of selenium by tomato fruit and leaves increased.(3)Soil application of selenium 2 mg/kg combined with foliar application of methyl jasmonate 0.2 mmol/L significantly changed the composition and structure of tomato fruit and leaf microbial communities,the Shannon index and Chao-1 index of tomato leaves were significantly higher than those of control leaves.Beneficial bacteria such as:Methylobacterium,Sphingomonas are enriched on tomato leaves.(4)Fifteen bacteria were isolated from the tomato phyllosphere in the treatment group of soil application of 2 mg/kg selenium combined with foliar application of methyl jasmonate 0.2 mmol/L,and were cultured against Botrytis cinerea respectively,and then effective antagonistic bacteria were obtained.The identified antagonists were Bacillus subtilis and Bacillus velezensis.Spraying antagonistic antibiotics to tomato leaves significantly inhibited the incidence of tomato gray mold.When the leaves were inoculated with Botrytis cinerea spores,the mixed bacterial suspension of Bacillus subtilis and Bacillus velezensis was sprayed,which reduced the incidence of leaves from40.63% to 12.50%.