纯化的苏云金杆菌00-50-5晶体和芽孢对甘蓝尺蠖的杀虫活性

Insecticidal Activity of Pure Bacillus thuringiensis Strain 00-50-5Crystals and Spores against Trichoplusia ni Hubner

苏云金杆菌(Bacillus thuringiensis,Bt)00-50-5菌株可以高效地杀死多种鳞翅目昆虫害虫。为了深入研究该菌的治病机理和作用方式,首先需要分离和纯化晶体和孢子,研究它们的杀虫活性。本研究用纯化后的00-50-5菌株晶体和芽孢,比较它们对昆虫甘蓝尺蠖(Trichoplusia ni)的杀虫活性。初步的活性测定结果证实,在用100μg/mL浓度处理48 h后,00-50-5菌株纯晶体以及晶体和孢子混合物都能够杀死二龄甘蓝尺蠖幼虫,死亡率达100%,纯芽孢则无毒杀效力。致死中浓度(LC50)的测定结果表明,Bt 00-50-5菌株纯晶体的杀虫活性(LC50=0.32μg/mL)高于晶体和孢子的混合物(LC50=0.48),然而纯孢子的杀虫活性是非常低的(LC50大于500.00)。因此,00-50-5的晶体主要负责引起幼虫的死亡。

Bacillus thuriniensis （Bt） 00-50-5 strain can kill many Lepidopteron insect pests efficiently. At the first we need to isolate and purified crystals and spores, and then compare their insecticidal activities in order to further study its pathogenic mechanism and the mode of action. In the present study we compared their insecticidal activities against the insect target insect Trichoplusia ni larvae. The primary bioassay results demonstrated that using 100 g/mL of the concentrations, either the mixture of pure crystals and pure spores, or only pure crystals could kill T.ni larvae and resulted in 100% of the mortalities 48 h after treatment; however the pure spores could not kill the larvae. Next, the bioassay results also showed that the insecticidal activity is （LC50=0.32 g/mL） is higher than the mixture of crystal sand spores （LC0. 48）, the spores have a very low activity （LC50 more than 500.00）. Therefore, the crystals are primary responsible for causing death to the larvae.