棉铃虫对Bt生物农药早期抗性及与转Bt基因棉抗虫性的关系

用饲料感染法建立了棉铃虫Helicoverpa rmigera(Hubmer)敏感品系(SUS1)对Bt生物农药的敏感毒力基线和区分剂量，1995年测定了五省六县棉铃虫初孵幼虫对Bt生物农药的敏感性，结果表明：山东阳谷、河北邯郸、河南新乡、安徽萧县及江苏丰县棉铃虫已产生早期抗性，抗性个体百分率为5%～10%，与敏感品系相比，LC₅₀值稍有增加，但斜率b值明显变小；而江苏东台棉铃虫仍属敏感。这是国内外首次诊测到棉铃虫对Bt生物农药抗性。用棉叶喂饲法测定比较了转Bt基因棉花品系对不同种群棉铃虫的抗虫性效果，结果表明：用早期抗性的阳谷和新乡棉铃虫初孵幼虫接虫5d后平均死亡率较敏感品系下降16%～29%，说明棉铃虫对Bt农药与转Bt生物基因棉花品系间存在交互抗性。还讨论了Bt农药的抗性治理对策。

EAPLY RESISTANCE OF HELICOVERPA ARMIGERA (HUBNER) TO BACILLUS THURINGIENSIS AND ITS RELATION TO THE EFFECT OF TRANSGENICCOTTON LINES EXPRESSING BT TOXIN ON THE INSECT

Susceptible bioassay base line and discrimination doses for biopesticide Bacillus thuringiensis (Bt) on susceptible strain (SUS1) of Helicoerpa arrnigera(Huibner) with the diet infection method were established. The susceptibilities to commercial Bt subspecies kurstaki formulation in newly hatched larvae of H. arrnigera collected from six counties of five provinces were tested in 1995. The results indicated that the five populations of H. armigera from Yanggu (Shandong), Handan (Hebei), Xinxiang (Henan), Xiaoxian (Anhui) and Fengxian (Jiangsu) showed early resistance to Bt.The proportion of resistant individuals in this insect at the 5 locations was 5%-10%;LC₅₀ values increased slightly but the slope (b) decreased significantly as compared with those of susceptible strain. However, Dongtai population (Jiangsu) was still susceptible. The biopesticide Bt resistance of H. armigera was diagnosed for the first time. The effects of trangsgenic cotton lines expressing Bt toxin on various populations of H.Armigera with foliage-feeding method were also determined. The results indicated the average mortality of newly hatched larvae of H. armigera (Yanggu and Xinxiang) with early resistance to Bt declined significantly (about 16%-29%) compared with those of susceptible strain. It's suggested that populations of H. armigera from Yanggu and Xinxiang were resistant to biopesticide Bt and transgenic cotton expressing Bt toxin.The resistant management strategy of biopesticide Bt is discussed.