Studies On Wilt Toxin Of Verticillium Dahliae And Its Differentiation In Pathogenicity

Verticillium dahliae kleb. is the worldwide soil-borne fungus which causes severe vascular wilt in more 660 hosts Verticillium dahliae kleb is one of the most serious diseases of cotton in china, which seriously threatens the sustainable development of cotton production.In order to explicit the pathogenicity of Verticillium dahliae and to provide the theoretical testimony for the aberrance rule of pathogen. We carried out the research to pathogenicity variation of pathogen, biological characters and study of toxin to Verticillium dahliae kleb and the main results were obtained as follows:1.Four cotton cultivars were individually inoculated with 30 representative Verticillium dahliae kleb. Results showed that there was obvious difference in pathogenicity among those testing isolates There was also obvious difference in pathogenicity even if different hosts were inoculated by the same. Verticillium dahliae Based on the host reaction and clustering analysis of disease severity, the isolates of Verticillium dahliae could be divided into three categories: strong pathogenicit (pathotypeⅠ),medium (pathotypeⅡ) and weak pathogenicity (pathotypeⅢ) respectively。2.The biological characteristic studies with 30 representative strains shown that the V dahiae in the same field exist modal difference. There are three cultural type: black (sclerotium type), white (filamentous fungus) and middle. Furthermore, the growth quantity, formation of micro-sclerotium, fabric, color, size and relative amount of melanin of colony of those 30 representative strains of V. dahliae were different3.The temperature mensurate shows that the optimal temperature for V. dahliae is 25℃and a few strains can quickly grow in 28℃, However all strains grow slowly in 15℃and 30℃.4.The result of toxin resesrch indicate:the optimal codition for the toxin is Czapck's liquid substrate ,25℃,15d with surging.Seventeen amino acids were analyzed in the filtrate of V. dahliae toxin and the content of acidic aminophenol are more than alkalescent The V. dahliae not only produce toxin but also exert important effect. It can restrain cotton seeds from bourgeoning and bring obvious wilt,having affinity with concentration.