Table 1. Efficacy of native Bt toxins Cry2Ab, Cry1Ab, Cry1Ac and genetically modified Bt toxins Cry1AbMod, and Cry1AcMod against a resistant strain (BX-R) and a susceptible strain (APHIS-S) of pink bollworm.
| Strain | Toxin | n | Slope (SE)a | LC50 (95% FL)b | RRc | Survival (%)d |
|---|---|---|---|---|---|---|
| BX-R | Cry2Ab | 600 | 0.94 (0.2) | 90.3 (50 - 180) | 210 | 81 |
| Cry1Ab | 240 | NAe | 28.1 (NA) | 27 | 100 | |
| Cry1Ac | 720 | 3.8 (0.7) | 113 (82-150) | 310 | 88 | |
| Cry1AbMod | 414 | 3.4 (0.5) | 1.67 (1.1-2.3) | 1.6 | 0 | |
| Cry1AcMod | 720 | 4.2 (1.2) | 2.63 (1.6-3.2)f | 2.1 | 0 | |
| APHIS-S | Cry2Ab | 480 | 2.4 (0.4) | 0.438 (0.21-0.65) | 1.0 | 0 |
| Cry1Ab | 240 | 3.9 (1.1) | 0.103 (0.060-0.14) | 1.0 | 0 | |
| Cry1Ac | 600 | 3.1 (0.5) | 0.363 (0.27-0.45) | 1.0 | 0 | |
| Cry1AbMod | 390 | 2.3 (0.4) | 1.07 (0.43-1.7) | 1.0 | 0 | |
| Cry1AcMod | 720 | 1.9 (0.3) | 1.24 (0.093-2.3)f | 1.0 | 0 |
a
Slope of the concentration-mortality line with its standard error in parentheses
b
Concentration killing 50% with 95% fiducial limits in parentheses, in µg toxin per ml diet.
c
Resistance ratio, the LC50 for a strain divided by the LC50 for APHIS-S for the same toxin.
d
Survival at 10 µg toxin per ml diet adjusted for control mortality, n = 40 to 120 (mean = 82) larvae for each estimate.
e
Not available
f
90% fiducial limits, 95% fiducial limits not available