Combining Biocontrol Agents For The Control Of Fusarium Wilt And Verticillium Wilt

The purpose of this research was to screening the superior combining strains which controlling Fusarium wilt and Verticillium wilt effectively and promoting the growth of crops. Through reaffirming the biocontrol characteristics of many strains with different mechanism, and determining their effects on seed germination and the compatibility between strains, several strains with superior comprehensive characters were elected for combining. Coordination-control effects on Fusarium wilt and Verticillium wilt and growth-promoting effects on plants, of combining strains, were further discussed. All these will provide the basis for developing new biocontrol preparations controlling Fusarium wilt and Verticillium wilt.According to the results of reaffirming the biocontrol characteristics of 11 strains (Non-pathogenic Fusarium Oxysporum strain 47 (Fo47); Soil Actinomycete SC11, 153, A4, SC1, SE2; Endogenous Actinomyces AM3, SF6, SG2; Hyperparasitic Actinomyces PR, F46),such as inhibition activities in vitro, fungicide resistance and colonization ability,and the assessments of affecting seed germination,they were shown that: comprehensive performance of 8 strains (Fo47, SC11, 153, A4, AM3, SF6, SG2, PR) were stable, and were determine as alternative strains for combination design.The compatibility of 8 strains (Fo47, SC11, 153, A4, AM3, SF6, SG2, PR) between each others, was defined by mixed culture. The differences in growth of biocontrol strains that were cultivated in mixed culture and monoculture were compared by analysis of their growth and consumption curves. The results showed that: in addition to strains A4 and AM3 which were uncompatible with most other strains, strains Fo47, SC11, 153, SF6, SG2 and PR were compatible with each other, and these 6 strains were eventually as the combining strain. Moreover, associating this test results with many years researches of our laboratory, strains 153, SC11 and Fo47 were as leader and other strains as assistant, combining the strains on the basis of their different mechanism, 30 combinations were constructed in total.In order to enable 6 strains (Fo47, SC11, 153, SF6, SG2 and PR) to exert biocontrol well, and to stabilize and improve the field control effect respectively, we prepared the biocontrol agent powder using shallow tray fermentation and fermentation conditions of 6 strains were optimized. Eventually, biocontrol agent powder was obtained with higher biocontrol activity and facilitating the field application.The inhibition activities of individual and combining strains in vitro were tested by cylinder-plate method and using Fusarium oxysporium f. sp. niveum, Verticillium dahlia and Fusarium oxysporium f. sp. vasinfectum as target pathogens. The results showed that 10 combinations(B₅, B₇, B₈, B₉, C₃, C₇, C₈, C₁₀, D₅, D₇)displayed obviously antagonistic effects on 3 target pathogens, and there were differences. Also it was shown that the combinations were not always enhancing the inhibition activities, still weakening, which compared with single strain. And further demonstrated that there was no correlation between the numbers of combining strains and the inhibition activities.In greenhouse experiment, the control effects of combinations on Watermelon Fusarium wilt and Eggplant Verticillium wilt were improved to varying degrees compared with individual strains, and were different along with the numbers and kinds of strains, the same strain in different combinations performed diversely. 4 of the 30 combinations (B₇, C₉, D₄, D₇) showed significant and were the best, the control effects of the 4 combination were greater than 60% on two kinds of plant disease.While researching the growth-promoting effects on watermelon and eggplant, we found that the effects of other treatments on emergence rate of two kinds of plants were not significant difference,excepting A4 and the combinations B9, C10 and D8. Most of the combinations exhibited growth-promoting effects to different degree. The growth promotion of combining biocontrol stains (B₃,C₁,C₃,C₉,D₂,D₅,D₆,E₁) was significantly higher than the best individual A4. Furthermore,we found that the combination D₄ restrained the growth of watermelon, the combinations B1, B5, B8, C7 have the negative effects on physiological indexes of eggplant and reached significant level.