Objective]In this study,ultraviolet irradiation was used to mutate Beauveria bassiana BH01,isolated from an infested larvae of Hyphantria cunea ( Drury) ( Lepidoptera: Arctiidae) ,to select high virulent mutants and provide new engineered strains for the biocontrol of H. cunea.[Method]The spore suspension of BH01 was put under UV lamp to mutagenize,positive mutant strain was first selected based on the mutation strains’spore yield which was more than 2 times of original strains. Then the pathogenicity of positive mutant strains to 5th instar larvae of H. cunea was determined. The screened high virulent mutant strains were subculture to determine the stability of the sporulation yield and pathogenicity. [Result]We obtained 28 colonies after UV treatment,and the corrected mortality of spore was 85. 5%. The colonies acquired after UV treatment were cultured on PDA plate and three positive mutant strains of BH01-5 ,BH01-12,and BH01-25 with more than 2 times higher spore yield than the original strain were obtained. Contrast to the original strains,the corrected mortality of 5th instar larvae of H. cunea caused by the mutant strain BH01-5 was significantly lower, and BH01-25 caused the almost equivalent mortality. However,the BH01-12 caused the significantly higher mortality, and the corrected mortality and LT50 values were 1. 30 and 0. 68 times higher than that of the original strain,respectively, and the differences are statistically significant. The mutant strains BH01-12 and BH01-25 were subcultured 6 generations. The results showed that the spore yield and pathogenicity of BH01-25 decreased gradually,with the same trend with the original strain. But the spore yield was always higher than that of the original strain. In addition,the pathogenicity of original strain decreased from the 4 generation,while that of BH01-25 decreased from the 6 generation,indicating the better stability of the mutant. In contrast,both the amount of spore production and the pathogenicity to the larvae of H. cunea of the mutant strain BH01-12 were not declined during the 6 generation of subculture,indicating the mutant was significantly better than that of original strain. [Conclusion]After the UV mutagenizing to B. bassiana BH01 isolated from diseased larvae of H. cunea,a mutant strain BH01-12 with higher spore yield and pathogenicity was obtained. During 6 generation sub-culture of the mutant,the spore production and pathogenicity of BH01-12 had no any reduction, showing to a certain degree genetic stability and good production and application prospects.%【目的】对分离自美国白蛾幼虫虫尸的1株白僵菌菌株 BH01进行紫外线诱变，以获得高毒力突变株，为美国白蛾的生物防治提供新的工程菌株。【方法】将白僵菌的孢子悬浮液置于紫外灯下进行诱变处理，诱变处理后获得的菌株进行培养后以产孢量超过原始菌株2倍以上作为依据筛选正向突变菌株，测定其对美国白蛾5龄幼虫的致病力，筛选高毒力突变株进行继代培养，研究其产孢量和致病力的稳定性。【结果】对原始菌株 BH01经紫外线诱变处理后获得28个菌落，孢子校正死亡率为85.5%，将获得的菌落重新接种于 PDA 平板上得到产孢量高于原始菌株2倍以上的正突变株 BH01-5、BH01-12、BH01-25。其中诱变菌株 BH01-5对美国白蛾 5龄幼虫的校正死亡率明显低于原始菌株，BH01-25与原始菌株相当，而 BH01-12的校正死亡率和 LT50值分别为原始菌株的1.30和0.68倍，具有显著差异。将突变株 BH01-25和 BH01-12继代培养6次，发现诱变菌株 BH01-25菌株在继代过程中产孢量和致病力明显降低，表现出与原始菌株类似的趋势，但其产孢量始终高于原始菌株，另外，原始菌株培养第4代时即开始降低，BH01-25至第6代时才出现明显的降低，表现出了更好的稳定性。诱变菌株BH01-12在试验的6代继代培养过程中，无论产孢量还是对美国白蛾幼虫的致病力方面均未出现下降，且均明显优于原始菌株。【结论】经过对分离自美国白蛾幼虫的1株球孢白僵菌 BH01进行紫外诱变，得到了产孢量和致病力均高于原始菌株的突变株BH01-12，该菌株经过继代培养后，其产孢量和致病力均未出现降低，表现出一定的遗传稳定性，具有很好的生产和应用前景。
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