The Preliminary Mechanism Of Trichoderma Harzianum T2-16 Against Fusarium Wilt Of Watermelon

In this study,three concentrations?mixed soil?A?,soaking seed?B?,no treatment?CK??of 105 g-1 T.harzianum T2-16 were used to evaluate the effects of T.harzianum T2-16 on watermelon fusarium wilt by the incidence and growth potential of Fusarium wilt in Zaojia"8424",the dynamic changes of colonization of T.harzianum T2-16 in watermelon roots,the enzyme activity and microbial community structure of rhizosphere soil.At the same time,to explore its preliminary mechanism of prevention and control,so as to provide theoretical basis for watermelon fusarium wilt prevention.The results of the experiment are as follows:1.Two treatments of T.harzianum T2-16 also can effectively inhibit the occurrence of watermelon fusarium wilt and promote the growth of watermelon plants.30 days after plant planting,the occurrence degree of watermelon Fusarium wilt tended to be stable.Among them,treatment A had the best control effect on watermelon Fusarium wilt,and its relative control effect reached 67.41%.In addition,the average trailing length and aboveground fresh weight of watermelon per plant in this treatment was 87.25 cm and35.86 g,which was 54.20%and 179.07%higher than that in CK,respectively.2.The optimal transformation system of T.harzianum T2-16 was 20?,1000 ug/ml G418 which was established by protoplast-mediated genetic transformation systerm by PEG-CaCl₂,and successfully obtained the transformed strain TG2-10 which can stably express green fluorescent protein.It was found that there were no significant differences in growth rate,sporulation,biocontrol effect and colony morphology between TG2-10and wild type strains.Using laser confocal microscope,it was found that the transformed strain TG2-10 could infect and effectively colonize the root tissue of watermelon,and form a reticular structure in the root twining of watermelon.3.The Trichoderma and Fusarium oxysporum f.sp.Niveum?Fon-1?were detected by real-time fluorescence quantitative PCR,The results showed that the numbers of Trichoderma in rhizosphere soil increased 10 times as much as that in CK,and maintained a stable level throughout the course of onset,after the application of T.harzianum T2-16.At the same time,with the occurrence of watermelon Fusarium wilt,the number of FON in rhizosphere soil and root system of watermelon changed significantly.The number of FON in rhizosphere soil of treatment A increased at first and then decreased,and the number of FON in watermelon root was lower than the lower limit of quantitative detection.On the contrary,the number of FON in the rhizosphere soil of watermelon treated with CK decreased at first and then increased,and the number of FON in watermelon root increased at first and then decreased.The results showed that T.harzianum T2-16 could induce the proliferation of Trichoderma spp.and to effectively prevent the infection of watermelon plants by FON.4.The application of T.harzianum T2-16 in soil could effectively increase the number of culturable bacteria and actinomycetes and reduce the number of culturable fungi,and the effect was the most obvious at the peak period of onset.At the same time,the enzyme activity of watermelon rhizosphere soil showed that T.harzianum T2-16 could increase acid phosphatase?S-ACP?and sucrase?S-SC?in soil to varying degrees.Cellulase?S-CL?and catalase?S-CAT?activities.With the occurrence of watermelon Fusarium wilt,the enzyme activity of rhizosphere soil changed in varying degrees.Among them,the activities of S-ACP and S-CAT increased at first,then decreased and then increased,the activity of S-CL increased to the peak of the disease,and the activity of S-SC decreased gradually,while the activity of S-SC increased significantly.5.The application of T.harzianum T2-16 in soil can increase soil bacterial diversity and reduce soil fungal microbial diversity,Through the high throughput sequencing analysis.The results showed that T.harzianum T2-16 could significantly reduce the abundance of bacteria such as Mizugakiibacter,Jatrophihabitans and Gemmatirosa in soil,Increase the richness of Sphingomona,Streptomyces and Pseudomonas,among them,the richness of Pseudomonas increased by more than 130 times.With the changes in fungal communities,Trichoderma was maintained at 48.98%-70.48%richness in treatment A,but 0.74%-2.54%in CK,it was further suggested that T.harzianum T2-16 could colonize stably in soil and watermelon rhizosphere.In addition,T.harzianum T2-16could reduce the abundance of Penicillium,Chaetomium and Aspergillus.At the same time,it was found that Sphingomonas,Streptomyces,Pseudomonas and Trichoderma,Arthrographis,Talaromyces in soil were negatively correlated with the incidence of watermelon Fusarium wilt.But Jatrophihabitans,Escherichia-Shigella,Gemmatimonas and Chaetomium,Dendroclathra,Zopfiella were positively correlated with the incidence of watermelon Fusarium wilt.