Control Effects And Mechanism Research Of Cotton Endophytic Fungi Against Verticillium Wilt In Gossypium Hirsutum

Cotton Verticillium wilt is a very serious vascular disease, and caused great economic losses every year in the world. So far, there is no ideal method of prevention and control. Endophytic fungi exist in cotton plants, and can stably propagate and reproduce, which is their advantage compared with the exotic biocontrol fungi. Therefore, starting from the endophytic fungi in cotton, isolation and screening the strains with inhibitory activity and good control effect against Verticillium dahliae is worth exploring new ways to prevent and control cotton Verticillium wilt.In this study, 200 strains of endophytic fungi isolated from healthy cotton plants were as materials, and strong pathogenic strain Vd080 was as the target. Using the disc filter method, dual culture method and buckle culture method to screen high inhibition rate strains against V. dahliae, and determine the inhibition rate and the effects of metabolites of selected endophytic fungi on V. dahliae spore germination and yield. In greenhouse, control effects were detected by culture filtrate inoculation and substrate inoculation method. In addition, the expression level of defense genes in cotton leaves was detected by real-time quantitative PCR, and the DNA content of V. dahliae in cotton was detected by qPCR. The main results are as follows:(1)Two strains were screened, CEF-082 and CEF-559, respectively, and they had better inhibitory effect on V. dahliae. Among them, CEF-082 is Chaetomium globosum, and CEF-559 is Fusarium.(2)The metabolites of CEF-559 had great influence on colonial formation of V. dahliae, and the inhibition rate was 100%. The CEF-082 culture filtrate(CF) could inhibite V. dahliae spore yield, and inhibite rate was 70.5%; the inhibition rate of CEF-559 was 78.2% 4 days after treatment, 6 days later reached 63.9%.(3)In greenhouse experiments, disease index of cotton Verticillium wilt was reduced by matrix inoculation with CEF-082 and CEF-559, and control effects were more than 60%; in culture filtrate inoculation treatment, inhibition rates of CEF-559 and CEF-082 had reached more than 60%. Moreover, matrix inoculation with CEF-082 and CEF-559 had no negative effect on the growth of cotton, and CEF-082 could promote the cotton emergence.(4)CEF-082 and CEF-559 could up-regulate the expression of defense related genes, including ppo, pod, pal and β-1,3-glucanase. Moreover, CEF-559 also could up-regulate 4CL, basic chinase and acid chinase. β-1,3-glucanase, basic chinase and acid chinase played important roles in the process of plant resistance to disease, and the the product of them, glucanase and chitinase, could decomposite cell wall of pathogens.(5)DNA content of V. dahliae in cotton was detected by qPCR. The results showed that the culture filtrate of CEF-082 and CEF-559 could significantly reduce the DNA content of V.dahliae in cotton.In conclusion, the control effect of CEF-082 and CEF-559 against Verticillium wilt is better, so the active materials are expected to be made efficient and environmentally friendly microbial agents providing help for the control of cotton Verticillium wilt.