Abstract: To further improve control efficiency of Streptomyces catenulae XG40 on Phyllosticta citriasiana,the optimal ingredients of fermentation medium and suitable fermentation conditions in shake flask were determined by single factor and orthogonal experiments with mycelia quantity and inhibition zone as indicators.Then,the antifungal substances were crudely extracted from the cultural filtrate of XG40 with ethyl acetate and their physicochemical properties were determined.The results showed that the optimal fermentation medium formula for antagonistic strain XG40 was corn flour 50 g/L,soybean meal 9 g/L,yeast powder 6 g/L,NaCl 0.5 g/L,K₂HPO₄ 0.5 g/L,MgSO₄·7H₂O 0.5 g/L,and FeSO₄·7H₂O 0.01 g/L.The optimum fermentation conditions were initial pH value 7.0,temperature 28℃,loading volume 100/500 mL,inoculation amount 7% and rotational speed 160 r/min,and fermenting for six days.The crude extract by ethyl acetate exhibited high inhibition activity on the mycelial growth of P.citriasiana.Crude extract from strain XG40 had good stability to UV-irradiation at short time (180 min),acidic and alkali,and high storage stability in methanol solution,while high temperature had a certain impact to its inhibition activity.The above results indicated that the antagonistic strain XG40 could provide new raw materials for biological pesticides against P. citriasiana.The active component has good antifungal effect,and is stable and easy to preserve,which has a potential for further development and utilization.

Key words: Streptomyces catenulae XG40, Phyllosticta citriasiana, fermentation condition optimization, secondary metabolite, antifungal activity