Biological Characteristics Of Verticillium Dahliae Microsclerotium

Verticillium dahliae Kleb. is a widely distributed soilborne pathogen causing vascular wilt diseases on more than 660 plant species in 38 families. It causes serious damage to cotton and is difficult to control. It can survive as microsclerotia, the main inoculum of V. dahliae, for more than 10 years in soil. However, it is unclear for some important biological characteristics of V. dahliae microsclerotia. In this study, the optimum condition of microsclerotium formation and germination, lethal temperature of microsclerotia were investigated by using V. dahliae strain XJ2008. The main results were shown as below:1. The optimum condition of microsclerotium formation was established. The effects of medium types, pH value, and temperature on quantity and size of microsclerotium formation were studied using basal agar medium modified (BMM), with pH ranging from 9.5 to 11.5 and temperature of 20oC. Under this condition, 16 V. dahliae strains collected from Xinjiang, Jiangsu, Henan, Shaanxi, and Shandong were used to test the microsclerotium formation. The results indicated that they could produce abundant microsclerotia after inoculation for 12 days. The quantity and size of microsclerotia among those strains have significant difference, and no relationship with the pathogenicity of the strains.2. The optimum condition of microsclerotium germination was established by studying the effects of carbon source, pH value, and temperature. The optimal condition of microsclerotium germination were 20-25oC and pH 8 in distilled water. However, carbon source had no significant effect on microsclerotium germination compared with that in distilled water.3. The lethal temperature of microsclerotia was confirmed under different temperature intensity and time length. Results showed that microsclerotium germination rate was decreased with the treated time extending and temperature increasing. Microsclerotia possessed high temperature resistant characteristic, however, microslerotia almost lost its viability after being treated at 55-70oC for 180 min, which provided theoretical basis to manage Verticillium wilt of cotton by applying plastic film to increase soil temperature.