Isolation Purification And Identification Of Antagonistic Microbes And Biological Control Against Fusarium Wilt Of Watermelon

With the development of watermelon industry and the expansion of watermelon planting area, fusarium wilt of watermelon caused by the continuous cropping is becoming more and more severe. It severely restricts the watermelon production and farmers’ income. Fusarium wilt watermelon as the most serious soil-borne disease, receives more attention. Thus, the research on fusarium wilt of watermelon is of great importance to watermelon production. The traditional control method has some actual effect, however, based on it’s difficult to use and negative effect to the envirement, the simple biological control which is of high efficiency and environmentally friendly receives much concern. Using beneficial microorganism and antagonistic microorganisms to control and minimizethe occurrence of watermelon wilt is practical bio-control measures. The aim of this thesis is to select natural antagonistic microbes to highly efficiently control Fusarium wilt of watermelon, by combining a natural antagonistic microbe with organic fertilizer. The key results are as follows:Three strains of antagonistic actinomycetes, which were F22, F23 and F32 from the rhizosphere soil of the healthly growing pepper plant, were isolated and identified by serially diluting culture method and plate confronting method to identify the morphological characteristics, physiological and biochemical characteristics and molecular biology characteristics. The preliminary identification result showed antagonistic actinomycetes F32 and F23 were Streptomyces sp.and antagonistic actinomycetes F22 was Aeromonas media. In the antifungal spectrum experiment, wider antimicrobial spectrum of F32 strain was obtained than F22 strain and F23 strain, indicating a certain application potential in biocontrol. The range of temperature and pH which was suitable for F32 strain growth was wide, which the maximal growth condition was within the scope of pH7-8 in LB medium and PDA medium. Under the condition of liquid culture, the strongest antagonistic activity for F32 strain was found between pH7-8, where the culture temperature and duration exerted little effect on antagonism of F32 strain. The antagonistic activity of the spore suspension of F32 strain decreased when the dilution increased. Strains F22, F23 and F32 with obvious depressing effect were used to test antagonism, where the result indicated that control rate of 66.7% for strain F32 was found for inhibiting watermeon fusarium wilt of watermelon with 107cfu/gram soil of inoculation.Two strains of F32 and F23 combined with organic fertilizer were tested. Results indicated that the better control effect with F32 strain was obtainedfor single species inoculant biological organic fertilizer,70% of control rate was found at 108 cfu/g organic fertilizer Compared with the single species inoculant, the obviously increased control rate for mixed-agents was reached 79%. In addition, the increased plant height and enzyme activity of the watermelon seedlings were obtained for the biological organic fertilizer which demonstrated that the biological organic fertilizer has growth promotion effect.