Quantitative Bt ELISA assays have only recently become available as a research

tool. This research will not only assist cotton breeders in identifying lines which possess

more Bt is present, but indicate where agronomic and environmental factors impact on the levels of Bt in the cotton plant. Effects of crop nutrition, time of sowing, soil condition, soil water management etc have suggested that Bt efficacy is compromised to some extent when environmental stresses are imposed on transgenic plants. Hence, productivity of some Ingard cotton crops has been substantially limited.

Various projects in the past have attempted to assess the extent to which agronomic

factors influence Bt efficacy, including Project CRC3C (Dynamics of Bt protein in Ingard

cotton: mechanisms of variable efficacy against HeIicoverpa).

The primary aim of this project was to assess agronomic factors influencing the

amount of Bt toxin measured using quantitative ELISA assays. This would enable

identification of factors in agronomic experiments which influence Bt efficacy. Sampling of experiments involving crop nutrition, plant population and growth regulators etc. may provide a reasonable guide to indicate factors that influence the efficacy of INGARD cotton andprovide a basis for recommendations to growers.