Biocontrol Evaluation Of Trichoderma Atroviride H18-1-1 And H18-1-1-t Strains

Trichoderma spp.,which is widely distributed in nature,is a biocontrol fungus with broad application prospect,Trichoderma can produce a variety of bioactive substances which have antagonistic effects on plant pathogenic fungi,bacteria and insects,and can improve the resistance of crops,promote plant growth and increase agricultural production.Trichoderma is an important biocontrol strain,is widely used in agricultural biological control.Trichoderma atroviride H18-1-1 with good biocontrol effect was obtained by preliminary screening in our laboratory.The overexpression of the glycoside transferase Taugt17B1 gene in Trichoderma atroviride strain H18-1-1 was obtained by using the gene overexpression technique.In this study,Chinese cabbage was used as the target crop,the effects of two Trichoderma strains on the growth and disease resistance of Chinese cabbage were determined to determine the biocontrol effect of H18-1-1 and H18-1-1-t overexpressed strains.The main research results were as follows:(1)The results of the plate confrontation experiment on 8 main pathogenic strains showed that,the normal growth of the pathogen was inhibited.The original strain and the overexpressed strain had good inhibitory effect on the pathogenic bacteria.The strain H18-1-1-t was overexpressed against F.pseudograminearum and F.verticillioide.The effect is even greater with Gaeumanomyces graminis,Bipolaris so-rokiniana,and Fusarium proliferatum.(2)Greenhouse pot experiment and field experiment were used to determine the growthpromoting effects of the original strain and the overexpressed strain on Chinese cabbage.The dry weight,root length,leaf length and chlorophyll content of pak cabbages were significantly increased by the treatment of overexpressed strain H18-1-1-t and the spore suspension of wild-type H18-1-1.In addition,compared with wild-type H18-1-1,application of 10~6 spores/m L of overexpressed strain H18-1-1-t in spore suspension was more effective in promoting the growth of Chinese cabbage.Both potted greenhouse and field experiments have yielded similar results.(3)Greenhouse pot experiment and field experiment were used to measure the growth promoting effects of the original and overexpressed strains on Chinese cabbage.Compared with the control group,the over-expression strain H18-1-1-t and the original strain H18-1-1significantly increased the growth indexes of dry weight,root length,leaf length and chlorophyll content of Pakchoi,the effect of 10~6/m L spore suspension was more significant.However,there was no significant difference between the original strain and over-expressed strain at the same concentration.Similar results were obtained in greenhouse pot experiment and field experiment.(4)The results of pot experiment showed that the overexpressed strain H18-1-1-T had a higher control effect on the basal rot of Chinese cabbage than the original strain.(5)The results of the pot experiment and field experiment showed that the activities of superoxide dismutase,peroxidase and catalase and the expression levels of the genes encoding the defense enzymes in the leaves of Chinese cabbage could be increased by the overexpressed and the original strains.The overexpressed strain was significantly higher than the original strain in increasing the activity of defense enzyme and the expression level of defense enzyme encoding gene.The above results showed that both Trichoderma atroviride H18-1-1 and overexpressed strain H18-1-1-t could significantly improve the effects of disease prevention and growth promotion,the activities of defense enzymes and the relative expression of genes in Chinese cabbage,and the overexpressed strain had more significant biocontrol effects than the original strain.