Baseline toxicity of Cry1Ac toxin against spotted bollworm, Earias vittella (Fab) using a diet-based bioassay.

摘要

Baseline toxicity of Cry1Ac was determined for the spotted bollworm Earias vittella in India using a semi-synthetic diet. A total of 27 sites from 19 cotton-growing districts of north, central and south India were sampled during the 2002 and 2003 cropping seasons, and Cry1Ac diet incorporation bioassays were carried out to understand the geographical variability in the baseline susceptibility. The LC50 of Cry1Ac ranged from 0.006 to 0.105 micro g/ml of diet. The overall variability in toxicity was 17.5-fold between districts. The highest variability of 17.5-fold was recorded from districts of south India. However, the variability in majority (92%) of the strains was less than 10-fold. The bioassay response in the central and south Indian strains was consistent with a minimum variability at 3.6- and 2.5-fold, respectively.