中文摘要：

从印楝叶片中分离筛选获得1株对稻瘟病菌具有优异拮抗效果的内生放线菌YL-2.采用不同溶媒萃取法获得粗提物,试验结果表明：由乙酸乙酯萃取的粗提物抑菌效果最好,抑菌直径可达24.2mm;以此粗提物作为抑菌剂,采用悬滴法和抑制生长速率法,测定不同浓度时对稻瘟病菌的抑制活性.结果表明：粗提物对稻瘟病菌孢子萌发的抑制作用随浓度的增加而增强;在浓度为0.8g· L-1时,对孢子萌发抑制率为97％;而在浓度为1.6g· L-1时,对菌丝抑制率为92.2％.稳定性检测结果表明：随着温度的升高,粗提物的抑菌活性明显下降,室温时抑菌直径达到最大值（27.5mm）;在弱酸性条件下抑菌活性比较稳定,pH值为4.0条件下最稳定;粗提物对日光的稳定性较差,高度感光会逐渐失去活性.

英文摘要：

A strain of endophytic actinomycete （YL-2） was isolated from the leaf of Azadirachta indica A. Juss and was identified as Streptomyces rochei, It exhibited antagonistic activities against Pyricularia oryzae. Different solvents were used to obtain the crude extract, and ethyl acetate was shown to produce active substance with strongest inhibitory effect against Pyricularia oryzae showing an inhibitory diameter of 24.2mm. The methods of suspending and mycelium growth rate were adopted to study the effect of concentration of crude extract on Pyricularia oryzae. Results indicated that the inhibitory effect of the crude extract on spore germination of Pyricularia oryzae increased as concentration of crude extract increased. The max spore germination inhibition rate in 0.8g·L^-1 was 97%, and the mycelium growth inhibition rate in 1.6g·L^-1 was 92.2%. The stability of the crude extract was tested against heat, acid, alkali and sunlight. The inhibition effect decreased significantly as the temperature increased. The maximum inhibitory diameter was 27.5mm at room temperature. The crude extract had higher stability in weak acidic environment showing highest stability at pH of 4.0. The crude extract also had a low stability when exposed to sun light. It was highly sensitive to light and gradually lose its activity when exposed to light.