Isolation, Screening And Identification For Biocontrol Actinomycetes From Soil Samples

For utilizing antagonistic actinomycete strains to control Verticillium wilt, the researchisolated actinomycete strains from soil samples on GAO1th synthetic culture medium with50μg/mL K2Cr2O7, using soil dilution method. Using Verticillium dahliae, Fusariumoxysporum f. sp. vasinfectum and Fusarium oxysporum f. sp. niveum as target pathogens,antagonistic actionmycete strains were screened in vitro and in pot. The bioactivities ofantagonistic actionmycete strains were further studied through testing the antagonistic ability,colonization ability and fungicide resistance. In addition, the identification of the selectedstrains basing on analyzing morphological characteristics, cultural characteristics,physiological and biochemical characteristics had been done. The main results are as follows:50strains of actinomycetes were isolated from6samples of soil which collected frompesticides companies surroundings in Guangxi and Jiangsu province. By antagonism in petridish trials,6antagonistic actionmycete strains were preliminary screened, named JSGF4,JSGF10,GXDM6,JSCK14,JSJF7and JSJF5,which account for12%of the total numberof isolated strains. These antagonistic strains were mainly isolated from the fields of Jiangsuprovince.For inhibiting the mycelium growth and conidia germination, the results showed that thefermentation filtrates of the strains JSGF4,JSGF10and JSCK14have obvious antagonisticeffects on both mycelium growth and conidial germination for3target pathogens, and theinhibition rates of mycelium growth and conidial germination were all above60%. Thefermentation filtrates of the strain JSGF4had strong inhibiting effect on mycelium growth ofV. dahliae, with the inhibition rates as high as100%. In pot experiments, the control effects ofthose6actinomycete strains to V. dahliae were significant. Specifically, the control effect ofthe strain JSGF10was as high as74.55%, which suggested that the strain JSGF10has furtherdevelopment value in biocontrol against Verticillium wilt.The colonization ability results showed that those6strains could not colonize in thebody of plant, but could live in rhizospher. The strain GXDM6had the greatest colonizationability, with the spore concentration of3×106cfu/g in the soil. The results of antagonistic ability showed that all those6strains had inhibiting effects on diffrerent pathogens, especiallyto Ascomycota and Deuteromycetes. The results of fungicide resistance showed that all ofthose6strains have high resistence to50%Carbendazim,40%Quintozene and25%Qingxijunzhi. They could grow well even in500μg/mL fungicide. But they were all sensitiveto75%Chlorothalonil, and could not grow with the fungicide concentration as low as1μg/mL.Using the strain JSGF10as tested strain, the best nutrient solution was choosed throughweighing dry weight of the colonies which cultured in the three kinds of nutrient solution:millet, SNB and GAO1th synthetic culture, and testing the antagonistic ability offermentation filtrates of the strain to pathogens. The results showed that the GAO1thsynthetic culture was the best nutrient solution which could culture the most amount ofcolonies, and the fermentation filtrate had the strongest antagonistic activity.Based on morphological, cultural, physiological and biochemical characteristics, thestrain JSGF4was identified as Streptomyces rimosus, the strains JSGF10and JSCK14belonged to Streptomyces albus, and the strain GXDM6was Streptomyces griseus.This research indicated that antagonistic actionmycetes with high antagonistic activity,colonization ability and fungicide resistance could be obtained from special habitat. The strainJSGF4and JSGF10had significant inhibiting effects to Verticillium wilt, they could providethe theory basis in the application of control plant Verticillium wilt.