Identification and preliminary evaluation of a biocontrol actinomycete strain gz-8 against Colletotrichum gloeosporioides

An actinomycete strain gz-8 was isolated from Linyi, Shandong Province, which had a strong antagonistic effect against Colletotrichum gloeosporioides with the inhibition rate of 72.5%. Strain gz-8 was identified as Streptomyces badius based on the morphology, physiological and biochemical characteristics, combined with 16S rDNA sequence analysis. Strain gz-8 has a broad antifungal spectrum, with strong inhibitory effects on six plant pathogenic fungi. The inhibitory activity of the crude extract from strain gz-8 was evaluated. The fermentation broth extract exhibits obvious inhibitory effects on the mycelial growth (EC50=3.18 μg/mL) and conidial germination (IC50=1.92 μg/mL) of C. gloeosporioides, which had higher activity compared to the mycelium extract of strain gz-8. The fermentation broth extract had good thermostability and pH stability. The control effect of 1 000 mg/L fermentation broth extract to mango fruits infected with C. gloeosporioides was 35.94%, which had no significant difference with that of chlorothalonil at the same concentration(34.11%).