The Study On Antimicrobial Active Substances And Colonization Ability Of PGPR Strains In Continuous Cropping Cotton Field

A series of continuous cropping obstacle problems which included the large-scale cultivation cotton causing continuous cropping, accumulation of a large number of pathogenic bacterias in soil, soil borne diseases such as Fusarium Wilt, Verticillium Wilt aggravating, cotton of severe crop losses, greatly reducing economic benefits and so on were the problem urgently to be solved in cotton production. PGPR strain which was screened from the soil of cotton field in the early stage of the laboratory, had broad spectrum antagonist activity for Fusarium Wilt, Verticillium Wilt and Rhizoctonia solani, promoted cotton germination and seedling growth, was determined compatibility and identified its species in this research.The study studied the Colonization and stable performance of antagonistic strain in cotton root colonization and producing types and conditions of antibacterial substance, to develop good biocontrol agents, explore measures to provide the basis for the prevention and control of continuous cropping obstacle. The main results were as follows:By using the morphological, physiological and biochemical assay and 16 S r DNA and gry B gene amplification analysis to identify the PGPR strain 4-2 、 Muc-7 which had screened for having good resistance for the effect of continuous cropping cotton. The results showed PGPR strain 4-2、Muc-7 were identified as Bacillus subtilis, and the two strains had good compatibility.For 4-2, Muc-7 strain double antibiotic marker, Colonization was determined at different strain inoculation method, amount of inoculum, inoculation number of times, and other biocontrol agents combined application of different strains in soil colonization by pot experiment. The results showed that4-2 and Muc-7 srtains for single bacterium seed, irrigation root and double bacterias composite irrigation root could be colonized in the cotton roots soil. Filling the root was better than that of the seed, inoculated quantity and amount of colonization were positively correlated. In 10 days after the inoculation dramatically reduced microbial colonization period in time to fill it 1-2 times can significantly improve the microbial colonization and its stability. 4-2, Muc-7 strains to mix and mingle with trichoderma did not affect its colonization performance. Vaccination 4-2, Muc-7 also could promote the growth of cotton seedlings.Preliminary analysis of antibacterial substances for PGPR strain producing showed the strains 4-2 and Muc-7 could produce the antimicrobial active substances of bacteriocin. Synthesis gene itu C of inturin and surfactin gene srf A was positive by PCR.The combination single factor with multi-factor orthogonal test showed that PGPR strains 4-2, Muc-7produced shaking flask fermentation culture conditions of antibacterial active substances: shake bottled fluid volume is 50 m L/300 m L, initial p H value of 7 of NA medium, 40 ℃, 120 r/min table shake culture72 h.