Table 1.
Pathogenicity of strains to Btk-resistant and susceptible diamondback moth in leaf dip bioassays. (Data are LC50s with 95% CLs (ln spores ml−1). Superscripts indicate whether LC50s were significantly different among genotypes. RR is the resistance ratio—the untransformed LC50 of resistant insects ÷ LC50 of susceptibles. DLC is the dominance of resistance at the LC50 concentration, for log-transformed data this was calculated (LCF1-LCsusc.)/(LCres.-LCsusc.), with a maximum value of 1.0 [27]. Data for the C3s3 B. weihenstephanensis strain are not shown, as this strain did not kill any insects at any concentration. Predicted LC50s of the mixtures are based on the weighted harmonic means of the LC50s of their components [28].)
| strain/product | subspecies | LC50 for each larval genotype |
|||||
|---|---|---|---|---|---|---|---|
| susceptible | F1 (resistant father) | F1 (resistant mother) | resistant | RR | DLC | ||
| Dt 7.1.o | B. t. kurstaki | 9.37a (8.73, 10.0) | 11.6b (10.7, 12.45) | 12.0b (11.4, 12.6) | 14.3c (13.6, 15.1) | 144 | 0.49 |
| DiPel DF | B. t. kurstaki | 8.51a (7.73, 9.27) | 11.4b (10.6, 12.1) | 11.1b (10.5, 11.7) | 16.2c (14.0, 18.4) | 2230 | 0.36 |
| A2m21 | B. t. kurstaki | 9.33a (8.93, 9.73) | 10.2a (9.69, 10.7) | 9.87a (9.41, 10.3) | 14.8b (14.0, 15.6) | 244 | 0.13 |
| XenTari | B. t. aizawai | 11.1a (10.7, 11.6) | 12.2a (11.4, 12.9) | 11.0a (10.3, 11.7) | 12.1a (11.5, 12.7) | 2.63 | n.a. |
| BGSC 4I4 | B. t. entomocidus | 10.5a (10.1, 10.9) | 11.6b (11.1, 12.0) | n.a. | 11.3b (10.9, 11.6) | 2.13 | 1.0 |
| selection treatment | predicted LC50s, RR and DLC | ||||||
| DiPel DF + XenTari | 9.63 | 11.4 | 13.9 | 68.0 | 0.41 | ||
| ‘six strain’ | 11.6 | 13.4 | 16.2 | 97.5 | 0.40 | ||