Study On The Mechanism Of Exogenous Selenium And Silicon On Tomato Growth And Development And Resistance To Tomato Gray Mold

Botrytis cinerea is a fungal disease caused by botrytis cinerea,which spreads quickly,and flowers,fruits,leaves and stems can get sick during the whole growth and development cycle of tomato.In order to prevent the occurrence of Botrytis cinerea,a large number of pesticides are sprayed,resulting in serious environmental pollution.It has been a hot issue at the forefront of agricultural science to reduce environmental pollution and ensure food safety by breeding healthy tomato plants to form a self-protective barrier in tomatoes,thus resisting invasion by external pathogens.In this experiment,we investigated the effects of different concentrations of selenium（Se）and silicon（Si）on the growth characteristics and fruit quality of tomatoes using Solanum lycopersicum L.as materials,and explored the mechanisms of the effects of Se and Si on the disease resistance of Botrytis cinerea.There were six treatments in the previous experiment:T0:spraying with water;T1:spraying with 2mg/L Na₂Se O₃;T2:spraying with 4 mg/L Na₂Se O₃;T3:spraying with 1.5 mmol/L Na₂Si O₃concentration;T4:spraying with 2 mg/L Na₂Se O₃+1.5 mmol/L Na₂Si O₃;T5:spraying with 4 mg/L Na₂Se O₃+1.5 mmol/L Na₂Si O₃;At a later stage,four experimental treatments,CK,Se,Si and Se-Si,were set up to study the effect of exogenous Se and Si on the resistance of tomato leaves to Botrytis cinerea and the effect of post-harvest Se and Si soaking treatment on the resistance of tomato fruits to Botrytis cinerea according to the best Se and Si concentrations screened out.The main results of the study were as follows:（1）Through morphological and molecular biological identification,the pathogenic fungus causing tomato gray mold was clearly identified as Botrytis cinerea.Through the study of its biological characteristics,it was found that the suitable p H value for mycelial growth of Botrytis cinerea was 6.0,the suitable growth temperature was 25℃,the mycelium stopped growing and grew slowly when the temperature was≤5℃and≥35℃,and the light condition had no significant effect on mycelial growth.（2）Exogenous Se and Si had the effect of promoting plant growth.Compared with T0,the plant height increased by 18.19%and 15.29%in T5 and T2 treatments,respectively,and the stem thickness increased by 10.00%and 6.00%compared with T0.T5 treatment significantly increased leaf fresh weight and dry weight by 42.10%and 45.51%compared with T0,respectively,and chlorophyll increased by 15.21%compared with T0 in T5 treatment.（3）Exogenous Se and Si at appropriate concentrations significantly improved tomato fruit quality.Compared with T0,the single fruit weight and hardness of T5treatment increased by 41.16%and 43.75%,soluble protein content,soluble solids,soluble sugars,titratable acids and Vitamin C increased by 20.97%,88.38%,42.25%,44.13%and 48.51%,flavonoids and total phenols increased by 37.46%and 37.64%,and the content of Se and Si elements increased by 12.85%and 35.67%,respectively,compared with T0.（4）Under in vitro conditions,24 mg/L of Se and 120 mmol/L of Si applied alone and in combination inhibited Botrytis cinerea mycelial growth and disrupted the osmoregulation of its cell membranes,and also significantly inhibited the diameter of leaf and fruit Botrytis cinerea spots,indicating that Se and Si were used to inhibit Botrytis cinerea infection by inducing leaf and fruit disease resistance and suppressing Botrytis cinerea infestation on tomato.Leaf and fruit stress by the pathogen induced reactive oxygen species（ROS）accumulation in tissues,and exogenous Se and Si treatments increased soluble protein content and significantly inhibited malondialdehyde（MDA）content in leaves and fruits;increased superoxide dismutase（SOD）,catalase（CAT）,and peroxidase（POD）enzyme activities,initiated tomato immune responses,maintained reactive oxygen balance and induce disease resistance in cherry tomato leaves and fruits.Compared with Se and Si treatment alone,the Se-Si combination treatment increased enzyme activity more significantly and also promoted the accumulation of total phenols and flavonoids in fruits,indicating that exogenous selenium and Si treatment significantly increased antioxidant enzyme activity and production of antioxidant substances in tomato and improved disease resistance in cherry tomato.（5）The expressions of PR1 and PR2 genes of disease-stage related proteins in both leaves and fruits were increased after exogenous Se and Si treatments compared with the control group.Among them,the Se-Si combination treatment significantly increased the expression of PR1 gene in leaves and fruits infected with gray mold compared with the Se and Si treatment alone,which were 3.13 and 11.93 times higher than those of CK,respectively;the silicon application alone significantly increased the expression of PR2 gene in leaves and fruits,which were 3.24 and 8.61 times higher than those of CK,respectively.In summary,exogenous Se and Si can significantly improve the growth and development of plants,the quality of fruits and vegetables,and have a certain inhibitory effect on disease relief.To some extent,to avoid the risk of diseases encountered in the growth of fruits and vegetables,and reduce the problem of environmental pollution caused by improper prevention and control.