Study On Identification Of Actinomyces TAS-1 And Its Control To Rice Blast

Actinomyces strain TAS-1,which was screened from the soil collected from Tibet, showed high antagonistic activity against Pyricularia grisea (Cooke)Sacc.. The strain was identified as Streptomyces griseus Wakman & Henrici according to it's morphology, cultural characteristic, physiological and biochemical characteristics. This strain could grow in pH 4.0 ～ 11.5 and at the temperature of 7 ℃ ～ 5 0 ℃. The optimum pH and temperature for it's growth was 8.0 and 29℃, respectively.The strain TAS-1 could produce antagonistic substance inhibited the growth of P. grisea in liquid medium at rest fermentation culture but could not produce this antagonistic substance at shaking culture.The antagonistic substance of strain TAS-1 could be extracted from fermentation suspension by chloroform .The optimum ratio of chloroform and fermentation suspension was 1 : 2(v/v).Antagonistic substances produced by strain TAS-1 were varied with culture medium and culture condition. The No.1 liquid medium (lactose 15 g, dextrose 15 g, soybean powder 25 g, yeast extracts 5 g, NaCl 20 g, distilled water 1 000 mL, pH 7.2 ) was the best liquid medium for producing antagonistic substance by the strain in 16 tested culture medium. The conditions for producing antagonistic substances by the strain were pH 8.0 , supplying oxygen 90mL / 500mL ,at 29℃ and cultured 21 days in liquid medium .Strain TAS-1 could live on the surface of rice leaves. The number of strain TAS-1 on rice leaves decreased from first day to third day after inoculation, and then increased gradually from third day to ninth day, and from ninth day to eigteenth day gradually decreased to zero.The fermentation suspension of strain TAS-1 showed broad range spectrum antagonism against pathogenic fungi. Except for Fusarium moniliforme Sheld. and Sclerotium rolfsii Sacc. in fifteen tested pathogenic fungi, the other thirteen fungi, such as Pyricularia grisea (Cooke)Sacc, Exserohilum turcicum (Pass.) Lenonard & Suggs, Bipolaris maydis (Nishik. & Miyabe) shoem.), Phomopsis sp., Alternaria brassicae (Berk.) Sacc, Alternaria...