一株感染家蚕的高致病性白僵菌的筛选及复合诱变

Screening and compound mutagenesis of a highly pathogenic Beauveria bassiana strain infecting silkworm

摘要:

【背景】白僵蚕中的生物活性物质在医疗、保健品及化妆品行业有着广泛的应用。目前，许多人工养殖僵蚕基地在实际生产中使用的菌种多为未进行纯化优选的自然感病死亡僵蚕孢子粉且无固定的施用浓度，使得蚕的僵化死亡率难以保证。提高白僵菌菌株的致病力并筛选性状优良的高毒力菌株是工厂化生产白僵蚕研发的重要方向。【目的】利用紫外-微波复合诱变技术筛选高毒力菌株，为僵蚕工厂化生产提供优良菌株。【方法】利用孢子稀释法从山西省养殖农户中自然感染白僵菌的家蚕中分离获得一株原始白僵菌，运用紫外-微波复合的方式对该菌株进行诱变，并比较诱变前后菌株的产孢量及对家蚕的致病力。【结果】分离得到的原始菌株经鉴定为球孢白僵菌(Beauveria bassiana)，命名为Beauveria bassiana Bb1003。通过对致死率和正突变率的考察，确定紫外-微波复合诱变的最佳诱变条件为紫外(功率为15 W)照射30 min，微波(功率为800 W、额定微波频率2 450 MHz)辐照60 s。筛选后得到6株复合诱变菌株(UMCM1、UMCM2、UMCM3、UMCM4、UMCM5和UMCM6)。菌株UMCM2对家蚕的僵化率高达97.64%，产孢量是原始菌株的2.48倍，对家蚕的致病能力显著高于原始菌株。【结论】利用紫外-微波复合诱变的方式成功筛选到高毒力菌株，为工厂化生产白僵蚕奠定了基础。

Abstract:

[Background] The bioactive substances in batryticated silkworms (Bombyx mori larvae infected by the entomopathogenic fungus Beauveria bassiana) are widely used in medicine, healthcare, and cosmetic industries. At present, most of strains used in the production of batryticated silkworms are the spore powder from naturally dead batryticated silkworms without purification, and there is no fixed application concentration, which make it difficult to ensure the mortality of silkworms. It is an important direction in the research and development for industrial production of batryticated silkworm to improve the pathogenicity of B. bassiana strains and screen out highly pathogenic strains with excellent biological characteristics. [Objective] To screen out highly pathogenic strains by ultraviolet-microwave compound mutagenesis and provide elite strains for the factory production of batryticated silkworms. [Methods] A strain of B. bassiana was isolated with the spore dilution method from naturally infected domestic silkworms in Shanxi province. The strain was then mutagenized by UV-microwave combination, and the spore production and pathogenicity of the strain were compared before and after mutagenesis. [Results] The original strain obtained by isolation was identified as B. bassiana and named B. bassiana Bb1003. Considering the mortality and positive mutation rate, we optimized the mutagenesis conditions as UV (15 W) irradiation for 30 min combined with microwave (800 W, rated microwave frequency of 2 450 MHz) treatment for 60 s. Six mutated strains, including UMCM1, UMCM2, UMCM3, UMCM4, UMCM5, and UMCM6, were obtained after screening. UMCM2 caused an infection rate of 97.64% for silkworm, produced spores 2.48 times those of the original strain, and had significantly higher pathogenic capacity for silkworm than the original strain. [Conclusion] A highly pathogenic strain was produced by ultraviolet-microwave compound mutagenesis, which laid a foundation for the mass production of batryticated silkworms.