Abstract:Streptomyces purpeofuscus YSSPG3 with antagonistic effect on Arthrinium phaeospermum, the pathogen of hybrid bamboo blight, was isolated from rhizosphere of healthy hybrid bamboo in Sichuan. In order to confirm the potential biocontrol of antagonistic actinomycetes on plant diseases, the best liquid fermentation medium for S.purpeofuscus YSSPG3 was optimized by orthogonal array experiments. The inhibitory effect and control efficacy of S.purpeofuscus YSSPG3 on A.phaeospermum were tested with conidial germination, mycelial growth as well as lesion control in excised tissues and in field trial. The results showed that liquid fermentation medium had been screened out through optimization experiment, with ingredients of glucose 5 g, glycerol 5 g, soybean powder 3 g, peptone 5 g, NaCl 2.5 g, CaCO3 2 g, and distilled water 1 000 mL. The optimal fermentation filtrate had conspicuous inhibitory effect on conidial germination and mycelial growth. It was found that the germ tube and mycelium of A.phaeospermum exhibited obvious malformation after being treated with the cell-free fermentation filtrate. Development of lesions were inhibited remarkably on excised twigs and leaves which had been treated with the pure or 10 times dilution of cell-free fermentation filtrate and inoculated the mycelia cakes, the control efficacy of 4 days after inoculation was more than 70%. In the field trails, the control efficacy of spreading the pure or 5 times dilution of cell-free fermentation filtrate reached 80%, which was significantly higher than those of 50% carbendazim (30 mg/mL) and 70% thiophanate methyl (30 mg/mL) at P＜0.01 level.