Table 2.
Cross-resistance to Cry1Aa, Cry1Ab, and Cry2Ab of Cry1Ac-selected strains (AY2 and QX7) relative to a susceptible strain (SCD) of H. armigera.
| Strain | Bt toxin | LC50 (95% FL)* | Slope ± SE† | n | Resistance ratio‡ |
|---|---|---|---|---|---|
| AY2 | Cry1Aa | >80§ | NA¶ | 432 | >260 |
| Cry1Ab | 25.7 (14–90) | 1.3 ± 0.2 | 336 | 69 | |
| Cry2Ab | 0.338 (0.22–0.55) | 1.1 ± 0.1 | 384 | 5.9 | |
| QX7 | Cry1Aa | 31.6 (18–120) | 1.4 ± 0.2 | 240 | 100 |
| Cry1Ab | 12.7 (7.1–38) | 1.1 ± 0.1 | 288 | 34 | |
| Cry2Ab | 0.241 (0.20–0.30) | 1.6 ± 0.1 | 432 | 4.2 | |
| SCD | Cry1Aa | 0.313 (0.25–0.41) | 1.6 ± 0.2 | 312 | 1.0 |
| Cry1Ab | 0.373 (0.24–0.67) | 1.7 ± 0.2 | 336 | 1.0 | |
| Cry2Ab | 0.0575 (0.043–0.074) | 1.5 ± 0.2 | 336 | 1.0 |
*
Concentration of toxin (μg/cm2) killing 50% of larvae and its 95% fiducial limits.
†
Slope of the concentration–mortality line and its standard error.
‡
LC50 of a toxin for a strain divided by LC50 of the same toxin for susceptible strain SCD.
§
Mortality was 17% at 80 μg Cry1Aa/cm2 diet, the highest concentration tested.
¶
Not available.