Primary Study On Biological Characteristics Of Verticillium Dahliae And Biocontrol Of Eggplant Verticillium Wilt

Pathogens of the Verticillium wilt of eggplant were isolated from diseased stems in suburb of Yaan, Sichuan. 15 strains were obtained and identified to be Verticillium dahliae. The pathogenicity of these strains was tested , the results showed that the pathogenicity on the variety Meizhou daxk(Solanum melongen) was significant different among all the strains tested, and the strains could be divided into three pathotypes: I (strong), II (mild) and III (weak )strains, the frequency of type I was 46.67%, type II and III was 26.67% respectively.Study on Biological characteristics of V. dahliae showed that strains could grow among the range of 5³3℃, and the optimum temperature for growth and sporulation was 22.5℃. The suitable pH value for growth was pH6～7 and for sporulation was under pH4 and pH8. Sucrose was the better carbom source, KNO₃ was the better nitrogen source for growth and sporulation. Strains of hight pathogenicity had better growth and sporulation than those of weak pathogenicity. The optimum temperature and and pH value for spore germination were 25℃and pH5 respectively, the lethal temperature for the spore was 60℃ 10min. Spore germination was much more for hight pathogenicity strains than weak pathogenicity strains. The best conditions for microsclerotia germination were 25³0℃,pH5 and microsclerotia suspension. The lethal temperature of microsclerotia was 60℃20min. Microsclerotia germination was much more and heat resistance was stronger for weak pathogenicity strains than hight pathogenicity strains.The observations under light and scanning electron microscope revealed that the hyphae of V. dahliae could penetrate into epidermal cell of young eggplant roots from intercellular space, Elongation zone were the main penetration sites, Root tip and Root hair zone were the secondary penetration sites, Root cap could not be penetrated.The content of toxin protein produced in Czapck liquid medium cultrue was measured by the method of G-250, the results showed that the toxin production of each pathotype strains were significant different, pathotype I were higher than pathotypeIII, and there was positive correlation between toxin production and...