棉铃虫对Cry1Ac抗性的稳定性及其对适合度的影响

为明确棉铃虫Helicoverpa armigera（Hübner）对苏云金芽胞杆菌Bacillus thuringiensis（Bt）Cry1Ac毒蛋白抗性的稳定性及其适合度变化,利用生物测定的方法研究了Cry1Ac抗性品系棉铃虫转到正常饲料饲养后的抗性衰退及再次筛选后抗性的恢复情况,并比较了敏感、抗性和抗性衰退后各品系间的适合度差异。在失去选择压的情况下,高抗品系棉铃虫对Cry1Ac的抗性迅速衰退,经过4代后抗性水平由最初的3626.67倍下降到1436.67倍;到第12代时抗性水平已低于10倍,随后品系保持较稳定的低抗水平;当重新进行抗性再筛选时,其抗性水平可快速恢复,抗性倍数快速回升,5代后恢复到1123.33倍。与敏感品系相比,高抗棉铃虫品系的适合度明显降低,相对适合度仅为0.33,但转到正常饲料连续饲养14代后,棉铃虫适合度明显上升,相对适合度为0.87,主要表现为卵孵化率和幼虫存活率等显著提高。

Stability of resistance to Cry1Ac and its effects on relative fitness in Helicoverpa armigera

In order to explore the stabilities of resistance to Bacillus thuringiensis (Bt) Cry1Ac toxin in cotton bollworm Helicoverpa armigera (Hübner) and its changes of relative fitness, the resistance regressions of Cry1Ac-resistant strain after transferring to normal artificial diet and its resistance recovers after re-selection were determined using bioassay test, the differences of relative fitness among susceptible, resistant and regressive strains were also compared by measuring their biological characters. The results showed that the resistance of resistant strain (BtR, which had high resistance to Cry1Ac) decreased very rapidly when lost selection pressure, the resistance ratio reduced from 3626.67-fold to 1436.67-fold after 4 generations, the resistance ratio reached to less than 10-fold till 12th generation, after that it kept a relative stable low resistance level (BtR-D, resistance ratio was 6.67-fold). While the H.armigera in this BtR-D strain was re-selected using Cry1Ac, the resistance regained quickly and the resistance ratio in- creased to 1123.33-fold after reselection for 5 generations. Compared with susceptible strain (96S), the fitness of BtR was obviously lower, the relative fitness was only 0.33. However, after continuously reared on normal artificial diet for 14 generations, the fitness obviously increased, the relative fitness was 0.87, the major features were egg hatchability and survival rate of larvae were enhanced.