Cry1Fa对Cry1Ac抗性棉铃虫的毒力评价

摘要

为了防治多种鳞翅日害虫,表达Cry1 Fa的转基因玉米和棉花已在美国商业化种植.明确棉铃虫Helicoverpa armigera对Cry1Fa与Cry1 Ac的交互抗性及这两种杀虫蛋白之间的协同作用,可以为表达Cry1 Fa+Cry1 Ac的转双价抗虫棉花的合理应用提供依据.本实验测定了Cry1 Fa对棉铃虫敏感品系(96S)及用Cry1Ac筛选的抗性品系(BtR,抗性倍数2194.15倍)的毒力,发现Cry1 Fa对敏感棉铃虫的毒力远低于Cry1 Ac,LC50值是Cry1 Ac的504.80倍;而且抗性品系BtR对Cry1Fa存在19.98倍的交互抗性.Cry1 Fa与Cry1 Ac混用可以提高Cry1 Fa毒杀敏感棉铃虫的效果,尤其是Cry1 Fa浓度较低时,加入Cry1Ac,可以显著增加Cry1 Fa的毒力;但只有加入较高浓度的Cry1 Fa时才能增加Cry1 Ac的毒力.由于BtR品系已经对Cry1 Ac产生抗性,Cry1Ac对抗性棉铃虫的毒力明最降低;在较高浓度的Cry1Ac中加入Cry1 Fa可以显著增加棉铃虫的死亡率(P=0.0015,F=6.88,df=6),但最高死亡率仅为58.33％.D-饱和最优试验的结果证实,Cry1 Ac对于敏感棉铃虫的死亡率的影响达到显著水平(t1=13.76＞t0.os),Cry1Ac 与 Cry1Fa的交互作用对毒力的影响也达到显著水平(t22=2.42＞t0.05;t11=6.95＞t0.05;t12=3.43＞t0.05).Cry1Ac和Cry1Fa对抗性棉铃虫死亡率的影响都达到显著水平(t1=3.03＞t0.05;t2=2.59＞t0.05),但Cry1 Ac是决定抗、感棉铃虫死亡率的关键因素;Cry1Ac与Cry1 Fa最佳浓度配比范围都是1.41～2.10 μg/cm2;在抗性品系中,Cry1 Ac和Cry1 Fa的交互作用不显著.所以,尽管Cry1F+Cry1A作物扩大了杀虫谱,但棉铃虫对这两种蛋白存在交互抗性,而且这两种蛋白混用对治理抗Cry1 Ac棉铃虫的效果不理想,因此不建议在中国种植表达Cry1F+Cry1A的棉花.%Cry 1 Fa-expressing corn and cotton have been commercially planted in U. S in order to effectively control several Lepidoptera pests. Making clear the cross-resistance of cotton bollworms (Helicoverpa armigera) to CrylAc and Cry 1 Fa and the synergism between the two toxins could provide the theoretical bases for rationally applying CrylFa + CrylAc cotton. The toxicity of CrylFa to the susceptible strain (96S) and the resistant strain (BtR, selected by CrylAc, the resistance ratio was 2 194. 15-fold) was tested in our study. The results showed that the toxicity of CrylFa was lower than CrylAc to 96S, the LC50 value of CrylFa was 504. 80 times as high as that of CrylAc, and there was 19.98-fold cross-resistance to CrylFa in the CrylAc-resistant strain (BtR). CrylFa mixed with CrylAc could increase the toxicity of CrylFa against 96S, and especially when the concentration of CrylFa was low, the synergistic effect was significant. However, the toxicity of CrylAc could be improved just when being added with high-dose CrylFa. Because the BtR strain had resistance to CrylAc, the toxicity of CrylAc to BtR reduced obviously. Mixing CrylFa into high-dose CrylAc could increase the mortality of BtR (P -0. 0015 , F = 6. 88, df-6), but the highest mortality was only 58. 33% . The results of the 2-D-optimum orthogonal design experiment showed that CrylAc had significant effect to control the susceptible cotton bollworm (t, = 13. 76 > t0.05) , and the influence of interactive effect between CrylAc and CrylFa on toxicity was also significant (t22 =2.42 > t0.05; t11=6.95 >t0.05; t12=3.43 > t0.05). CrylAc and CrylFa had significant effect against the resistant cotton bollworm (t, =3.03 > t0.05; t2 = 2. 59 > t0.05) , but CrylAc was the key determinant for the mortality of the susceptible and resistant cotton bollworms. The optimum concentration ranges of CrylAc and CrylFa were 1. 41 - 2. 10 (jig/cm . However, the interactive effect between CrylAc and CrylFa was not significant in the BtR resistant strain. Thus, although the crops expressing CrylF +CrylA can expand the spectrum of killing insects, however, because of the cross-resistance and the undesirable effect in managing the CrylAc-resistant bollworm, transgenic CrylF + CrylA cotton is not recommended for planting in China.