Table 1.
Resistance to Cry1Ac and cross‐resistance to Cry1Aa, Cry1Ab, and Cry2Ab of LF256 relative to susceptible strain SCD of Helicoverpa armigera
| Strain | Bt toxin | LC50 (95% FL)a | Slope ± SE | RRb |
|---|---|---|---|---|
| LF256 | Cry1Ac | 6.71 (4.56–11.3) | 0.91 ± 0.16 | 224 |
| Cry1Ab | 8.25 (5.85–13.1) | 1.16 ± 0.18 | 34 | |
| Cry1Aa | >20c | NAd | >67 | |
| Cry2Ab | 0.36 (0.29–0.46) | 1.74 ± 0.19 | 1.5 | |
| SCD | Cry1Ac | 0.03 (0.02–0.05) | 1.12 ± 0.13 | 1.0 |
| Cry1Ab | 0.24 (0.14–0.36) | 1.39 ± 0.25 | 1.0 | |
| Cry1Aa | 0.30 (0.15–0.52) | 0.80 ± 0.26 | 1.0 | |
| Cry2Ab | 0.23 (0.11–0.56) | 1.72 ± 0.22 | 1.0 |
a
Concentration (μg toxin per cm2 diet) killing 50% of larvae and its 95% fiducial limits, n = 336 larvae tested from each strain against each toxin.
b
Resistance ratio = LC50 for a strain divided by the LC50 for the susceptible strain SCD.
c
Mortality was 17% at 20 μg Cry1Aa per cm2 diet, the highest concentration tested.
d
Not available.