荧光增白剂对Cry1Ac抗感棉铃虫围食膜的影响及增效作用

Effects of fluorescent brightener on the peritrophic membrane of Cry1Ac-resistant and Cry1Ac-susceptible Helicoverpa armigera larvae and the synergistic effects

为了提高Bt的杀虫活性,运用扫描电镜、SDS-PAGE电泳和生物测定技术,研究了荧光增白剂FB28对棉铃虫Cry1Ac抗性和敏感品系围食膜的影响及对Cry1Ac杀虫蛋白的增效作用。结果表明,正常棉铃虫围食膜表面光滑致密,没有空洞和缝隙。用含1%FB28的人工饲料饲喂刚蜕皮的5龄棉铃虫幼虫2 h后,抗感棉铃虫围食膜表面均出现许多空洞,且敏感棉铃虫的空洞明显大于抗性棉铃虫;随着处理时间的延长,围食膜上的空洞逐渐变小,13 h后恢复正常。用1%FB28离体或活体处理抗、感品系棉铃虫,均可造成围食膜蛋白被降解。用1%FB28与Cry1Ac杀虫蛋白混合饲喂抗、感棉铃虫初孵幼虫,可明显提高棉铃虫的死亡率,且对抗性品系的增效作用明显大于敏感品系,对敏感和抗性品系棉铃虫的增效比分别为2.23和9.34;1%FB28还可以明显增加对抗、感品系3龄棉铃虫幼虫的生长抑制作用。

In order to increase the insecticidal activity of Bt, the effects of fluorescent brightener 28 （ FB28 ） on the peritrophic membrane （PM） of Helicoverpa armigera larvae, and its ability to increase the toxicity of Bt insecticidal protein （CrylAe） in CrylAc-resistant and CrylAe-susceptible strains were studied using scanning electron microscopy, SDS-PAGE and bioassays. The results indicated that the sur- face of the normal PM was smooth and wrinkled without any pores or slits. While the 5th instar larvae were fed on diets containing 1% FB28 for 2 h, the surface of the PM in both resistant and susceptible strains exhibited many pores, and the pores in susceptible larvae were relatively larger than those in re- sistant larvae. The pores gradually shrank corresponding to the treatment time, and the disruptive effect returned to normal after 13 h. The PM proteins were dissociated in both resistant and susceptible strains after being treated by 1% FB28 in vitro or in vivo. Compared with the treatment using only Cryl Ac, the mortalities of larvae in CrylAc-resistant and CrylAc-susceptible strains could be obviously increased after they were fed on an artificial diet containing 1% FB28 and CrylAc. The synergic effect in the resistant strain was greater than that in the susceptible strain. The synergic ratios were 9.34-fold and 2.23-fold in Cryl Ac-resistant and Cryl Ac-susceptible strains, respectively. The 1% FB28 also significantly increased the effect on the 3rd instar larval growth inhibition in both resistant and susceptible strains compared with treatment solely by CrylAc.