Bt Toxin Variability in GM Cotton

GM cotton has been one of the most rapidly adopted transgenic crops. It is very effective in controlling target pests, and the benefits to the consumer and the environment have been well reviewed. There has been no report of product failures, but there are observations indicating that the efficacy of the transgenic to target lepidopteran pests may not be consistent during the growing season, said H. Dong and W. Li of the Cotton Research Center in China.

The researchers reviewed that the efficacy against target pests depends upon the expression of the Cry genes inserted in the cotton genome. The Cry genes may produce varying levels of the insecticidal Bt toxin depending on the plant age, plant structure or under certain environmental stresses - such as high temperature, salinity, or water and nitrogen deficiency. In instances where reduced insecticidal protein is observed, it may have been caused either by post translational regulation or due to methylation of the gene promoter.

Though all current Bt cotton cultivars are still effective in controlling target pests, Dong and Li suggest that developing new varieties with more powerful resistance, applying certain plant growth regulators, enhancing intra-plant defensive capability, and maintenance of general health of the transgenic crop are important in realizing the full potential of the crop.

The article was published by the Journal of Agronomy and Crop Science. Its abstract, with links to the full paper, can be accessed by subscribers at http://www.blackwell-synergy.com/doi/abs/10.1111/j.1439-037X.2006.00240.x.