TABLE 1.
Resistance development in H. zea when selected using activated toxin and MVP II
| Strain | Ga | Total no. of insects testedb | LC50 (95% FL)c | Slope (mean ± SE) | RRd |
|---|---|---|---|---|---|
| Activated toxin-resistant strain (AR) | |||||
| SCe | 800 | 9.13 (5.83-12.53) | 1.61 ± 0.41 | ||
| AR | 4 | 384 | 107.64 (75.37-155.6) | 1.42 ± 0.3 | 12.12 |
| SC | 480 | 8.89 (5.71-13.72) | 1.71 ± 0.41 | ||
| AR | 7 | 222 | 321.22 (251.27-371) | 1.89 ± 0.13 | 35.91 |
| SC | 384 | 8.94 (6.37-15.27) | 1.93 ± 0.31 | ||
| AR | 11 | 175 | 1,450 (690-2,392) | 1.42 ± 0.47 | 122.67 |
| SC | 384 | 11.82 (7.01-19.24) | 1.76 ± 0.42 | ||
| AR | 16 | 72 | —f | >100 | |
| SC | 384 | 13.90 (9.11-21.44) | 2.41 ± 0.51 | ||
| AR | 19 | 192 | 1,390 (743-12,017) | 1.39 ± 0.46 | 92.69 |
| SC | 192 | 15.00 (9.90-22.45) | 2.31 ± 0.52 | ||
| MVP II-resistant strain (MR) | |||||
| SC | 0 | 1,120 | 26.13 (16.34-35.62) | 1.73 ± 0.24 | |
| MR | 4 | 384 | 384.3 (282.31-568.12) | 1.79 ± 0.27 | 16.61 |
| SC | 640 | 23.13 (16.34-35.62) | 1.73 ± 0.24 | ||
| MR | 7 | 672 | 298.40 (155.16-455.5) | 1.67 ± 0.41 | 12.01 |
| SC | 1,120 | 24.84 (13.48-41.89) | 2.47 ± 0.57 | ||
| MR | 9-11 | —g |
a
G, generations of H. zea continuously selected with B. thuringiensis.
b
One to five replicates with one to seven concentrations.
c
LC50 values are presented in micrograms of B. thuringiensis protein per gram of diet. FL, fiducial limits.
d
The LC50 for AR divided by the LC50 for SC.
e
SC, susceptible colony.
f
47% survivors at 1.5 mg/g.
g
No selection due to reduced larval number; the resistant strain crashed after 11 generations.