Identification Of Antagonistic Actinomycetes And Its Control Effect On Cotton Verticillium Wilt In Xinjiang

Object:To select effective antagonistic actinomycete strains against Verticillium dahliae. in Xingjiang and make preliminary classification and identification about obtained antagonistic actinomycetes, finally, to make a first study on the biocontrol effect of these antagonistic actinomycetes against cotton verticillium wilt through pot experiment.Methods:In this experiment, the cotton disease occurred in Xinjiang were statisticed,andlO strains Verticillium wilt pathogen were isolated from cotton, they were identificated by the method of morphological and biological. there were24soil samples obtained from different cotton fields in Xinjiang. Cultured on Gause’s No.1aga medium, different Streptomyces were isolated from soil samples above by soil dilutionplate technique. All the isolates were tested for inhibitory activity against Verticillium dahliae on double-layer agar, and their inhibitory activity against cotton verticillium wilt was noted by the size of the inhibition zone. A further study to screen strains that had strong inhibition activity (inhibition diameter^15) to verticillium wilt of cotton was made by antagonistic trials of fermentation and Seeds radicle growth tests in Petri dish. Genome DNA of inhibitory Streptomyces was extracted with improved SDS method, then amplified by PCR using common primers of16S rDNA of actinomycetes and sent to sequence, next made gene sequence alignment about the results. Finally screened antagonistic actinomyces were preliminarily identified combining with physiological and biochemical characteristics and molecular biology methods. Further control effects of inhibitory Streptomyces was tested through pot experiments with two control, and each treatment was replicated three time. The morbidity was investigated after the onset of disease incidence.Results:1According to the survey data of cotton disease, the cotton verticillium wilt was one of the main problems of the cotton, MJ-XJ was identificated as Verticillium dahliae.2. There were561strains of actinomyces were obtained from24soil samples from different cotto n fields in Xinjiang and tested for their inhibitory activity against Verticillium dahliae. Among the m,59strains showed positive antagonistic activity. Through indoor plate confrontation screening,29of them had a strong antibacterial action (inhibition zone diameter≥15mm).3. Among them,5strains showed a strong antibiosis activity (inhibition zones≥17) in both tests of indouble-layer agar and the inhibition of the fermentation filtrate against Verticillium dahliae in vi tro, and the results suggested that TD3-2-1fermentation filtrate showed a high inhibition towards t he tested pathogenic fungu, and the bacteriostatic rate of the filtrate on the mycelial growth of V. dahliae was58.5%.4. TD3-2-1was Streptomyces(Streptomyces sp.) based on morphology, characteristic of culture, characteristic of physiology, biochemistry and the system development of16S rDNA5. Biocontrol bacteria on seed germination experiments showed that:the strain TD3-2-1had a significant growth-promoting effect on cotton seed. The result of studies for greenhouse control effect showed that: Compared with the control, the incidence and disease index of cotton verticillium wilt of cotton that was treated with antagonistic bacteria TD3-2-1were significantly reduced.Conclusion:Successfully isolated an antagonistic actinomycete strain, TD3-2-1, that had a significant inhibitory effect on Verticillium dahliae. TD3-2-1showed so good a antibacterial stability in vitro and in vivo experiments that can be used as a potential bio-control factors.