Abstract: To provided biocontrol germplasm resources for root rot disease in traditional Chinese medicine, screening, identification, and application evaluation of Streptomyces, an actinomycete with significant antibacterial effects against various Fusarium species, were carried out. The strain LQS-2 with significant antibacterial effect against Astragalus membranaceus root rot disease was screened from 120 strains of actinomycetes, and against the pathogenic bacterium F. moniliforme, F. solani N18-1-2, F. Verticillium 173, and F. oxysporum 295, the antibacterial rates each for 62.50%, 49.38%, 52.75%, and 67.50%. 16S rDNA sequence analysis and alignment showed that strain LQS-2 had the highest homology with the gene sequence of Streptomyces cellulosae, and combined with morphology, strain LQS-2 was determined to be S. cellulosae. The results of pot experiment showed that the greenhouse prevention effect of soaking the fermentation supernatant of S. cellulosiae LQS-2 combined with root irrigation on Astragalus membranaceus root rot disease was 69.50%. The field prevention effect of continuous root irrigation three times on Astragalus membranaceus root rot disease reached 76.02%, which was 2.55% and 18.76% higher than the control effect of microbial agents. After soaking in strain LQS-2, it showed a significant growth promoting effect on Astragalus membranaceus seedlings under greenhouse conditions. The root length, biomass, and underground dry weight increased by 37.58%, 20.00% and 33.33%, which compared to microbial agents. From this, it could be seen that S. cellulosiae LQS-2 has the potential to be developed as a biocontrol agent for the prevention and treatment of Astragalus membranaceus root rot disease.

Key words: Astragalus membranaceus root rot, Streptomyces cellulosae, pathogenic Fusarium, prevention and control effect