Abstract: To develop effective biocontrol products for controlling the root rot of Astragalus membranaceus, actinomycete strains with excellent prevention and controlling effects to pathogenic bacteria were isolated from the saline-alkali soil of Shule River basin, which were further combined into compound agents to improve the antibacterial effect on root rot of A. membranaceus. The plate tolimulus method and growth rate method were used to screen high-efficiency biocontrol actinomycete strains. Morphological characteristics, physiological and biochemical characteristics, and 16S rRNA DNA sequence analysis were used to identify strains. After that, a pot experiment was conducted to test the controlling effect on root rot of A. membranaceus. The results showed that among the total 244 tested strains of actinomycetes, 11 strains had inhibitory rates of more than 50% against the root rot disease. After rescreening, the inhibitory rate was 7%-57%. Combined with the screening effect and the inter-strain affinity test, the strains DA4-3-12, DA8-4-10 and 221 were used as the research targets for the compound strains. The strains DA4-3-12 and 221 were identified asStreptomyces alboflavus and strain DA8-4-10 as Streptomyces alanosinicus. Single strains DA4-3-12, DA8-4-10 and 221 and their compound strains in different combinations (DA4-3-12 + DA8-4-10, DA4-3-12 + 221, DA8-4-10 + 221, DA4-3-12 + DA8-4-10 + 221) all had controlling effects on root rot of A. membranaceus, and their control efficiencies were 60%, 46%, 70%, 55%, 70%, 64%, and 72% respectively. Among them, the compound DA4-3-12+DA8-4-10+221 had the best controlling effect. The synergistic effects of various strains in the mixed strains were fully expressed, with wide antimicrobial spectrum.

Key words: Fishery resource, Geographic information system, Spatial heterogeneity, Semivariogram, Spatial autocorrelation