对草地贪夜蛾高毒力的苏云金芽胞杆菌菌株筛选与杀虫活性研究

草地贪夜蛾是一种世界性重大农业害虫，给玉米等多种主要粮食和经济作物造成严重危害。为实现对草地贪夜蛾的高效、绿色、持续防控，亟需筛选高毒力苏云金芽胞杆菌菌株资源。本研究以前期实验室储备的对斜纹夜蛾、小地老虎具有杀虫活性的363株野生菌株库为候选菌株，基于菌株杀虫基因差异及进化关系，去除冗余菌株后获得172株候选菌株。通过培养获取这些菌株胞晶混合物，进行杀虫蛋白定量后，测定杀虫活性，获得27株对草地贪夜蛾初孵幼虫具有较高杀虫活性的菌株，其中菌株B14-D2的杀虫活性最高，LC₅₀为0.155 μg/g。克隆了该菌株中的cry1Ea3基因并在HD73^-无晶体突变株中表达，Cry1Ea3蛋白对草地贪夜蛾初孵幼虫LC₅₀为1.789 μg/g。本研究为新的Bt产品和杀虫基因的开发利用提供了丰富资源。

Screening and Insecticidal Activity of Bacillus thuringiensis Strains with High Toxicity against Spodoptera frugiperda

Spodoptera frugiperda (J. E. Smith), a major agricultural pest in the world, causes serious damage to many major food and economic crops, such as corn. It is urgent to screen highly virulent Bacillus thuringiensis (Bt) strain resources to achieve high-efficiency, green and sustained control of S. frugiperda. Based on the difference of insecticidal genes and the evolutionary relationships among strains, 172 candidate strains were obtained from the 363 wild strains by eliminating repetition strains, which were stored in the laboratory and showed insecticidal activity against Spodoptera litura and Agrotis ypsilon. The spores and crystal mixtures of these strains were obtained by culture. Their virulence against S. frugiperda was tested after quantification of insecticidal proteins, and 27 Bt strains were obtained for their high virulence. The most virulent strain was B14-D2, with LC₅₀ of 0.155 μg/g. The cry1Ea3 gene in this strain was cloned and expressed in crystal-free mutant HD73^-. The LC₅₀ of Cry1Ea3 protein against neonates of S. frugiperda was 1.789 μg/g. This research adds to the Bt strain resources for the development of new Bt products.