对美国白蛾高毒力苏云金杆菌菌株的筛选

为获得对美国白蛾(Hyphantria cunea(Drury))高毒力苏云金芽孢杆菌(Bacillus thuringiensis,Bt)菌株,本研究以43株Bt自然分离株为材料,经初步筛选和LC50测定得到了对美国白蛾幼虫高毒力菌株Bt S-19,在此基础上对该菌株的生物学特性进行了初步研究。结果表明,野生株间对美国白蛾活性差异明显,LC50测定结果经DPS软件分析,菌株Bt S-19活性最好,处理72 h后对初孵幼虫LC50值为1.8×105cells/mL,浓度对数回归方程为Y=1.082 9+0.744 4X,相关系数为0.988 8,明显好于标准菌株HD-1;对二龄、三龄、四龄和五龄幼虫72 h的LC50值分别为2.3×105、8.1×105、1.3×106和3.1×106cells/mL。光学显微镜下观察发现该菌株晶体为小菱形,生长对数期为2~5 h。推断该菌株是一株对美国白蛾有应用潜力的Bt野生株。

Screening of high toxicity Bacillus thuringiensis isolates against Hyphantria cunea(Drury)

The study was carried out among 43 Bacillus thuringiensis isolates against 1st larvae of Hyphantria cunea(Drury).The bioassay result indicated that the toxicity of these strains was different from H.cunea(Drury). And Bt S-19 isolate was the best among these strains by bioassay and DPS analysis,which was better than Bt subsp kurstaki strain HD-1.The LC50 of this isolate against 1st larvae of H.cunea(Drury) was 1.8×105 cells/mL and the regression equation of concentration logarithm was Y=1.082 9+0.744 4X in 72 h,relation coefficiency was 0.988 8;The LC50 of the isolate against the larvae of 2nd,3rd,4th,5th was 2.3×105 cells/mL,8.1×105 cells/mL,1.3×106 cells/mL,3.1×106 cells/mL respectively.The crystal shape of Bt S-19 was rhombus,and the logarithmic growth period was 2-8 h.This result suggested that Bt S-19 was presumably a potential wild strain against Hyphantria cunea(Drury) in practice in the future.