Abstract: Colletotrichum camelliae is an important pathogen causing anthracnose of tea plants. In order to obtain Streptomyces strains with better antagonistic effect on C. camelliae, the dilution coating method and plate standoff method were used to isolate and screen Streptomyces strains from the habitat of tea plantations. Morphological observation, physiological and biochemical characteristics and 16 S rRNA gene sequence analysis were combined to identify their species. Antimicrobial spectrum determination, mycelial growth inhibition test and spore germination inhibition test of C. camelliae were carried out for the isolated strains. The antifungal activities and stabilities of aseptic fermentation filtrate of the isolated strains against C. camelliae were determined by using the mycelial growth rate method. The extracellular enzyme-producing capacity, antimicrobial substance synthesis genes, volatile and non-volatile metabolite antifungal activity of the isolated strains were also determined. The results show that a strain XS-4 with better inhibitory effect on tea anthracnose pathogen was obtained and the plate inhibition effect on tea anthracnose pathogen was 76.42%. The strain XS-4 was identified as Streptomyces polychromogenes, which had good inhibitory effect on eight other plant pathogens and the antifungal properties have a broad spectrum. Scanning electron microscopy results show that the strain XS-4 could inhibit the growth of mycelium of tea anthracnose pathogen, and the mycelium was tightly entangled with each other and deformed. The spore germination inhibition test shows that the fermentation solution of strain XS-4 could inhibit the spore germination of C. camelliae, and the inhibition rate was 62.48%. The best fermentation medium for strain XS-4 was KMB medium, and the inhibitory active substance produced by 7 d incubation in KMB medium had the best inhibitory effect on tea anthracnose, the aseptic fermentation filtrate of strain XS-4 had a better stability to temperature, acid and alkali, ultraviolet, and protease. The non-volatile metabolites of strain XS-4 show better antifungal activity against tea anthracnose pathogen with aninhibition rate of 81.92%. The strain XS-4 has the ability to produce amylase, protease, β-1,3-glucanase, and cellulase. The pks-Ⅰ and pks-Ⅱ genes of strain XS-4 were associated with the production of antimicrobial substances. In conclusion, the strain XS-4 has a great potential for application in the biocontrol of anthracnose in tea plants.

Key words: tea anthracnose, Streptomyces, antifungal effect, stability, antimicrobial genes