Bt cotton in Pakistan: Post approval scenario of field performance

Germplasm and Genetic Stocks

poster

Cheema, Hafiza Masooma Naseer; Khan, Asif Ali; Ahmad, Sheraz; Speilman, David j.

Cheema, Hafiza Masooma Naseer

Cheema, Hafiza Masooma Naseer; Khan, Asif Ali

Genetically-modified, insect-resistant Bt cotton has been adopted extensively across Pakistan’s cotton-growing regions during the past decade, though formal approval for its release was only granted in 2010. As a consequence, Pakistan has seen the widespread adoption of unapproved Bt cotton. The main quality criteria for Bt cotton is the stable and sufficient expression of the transgene that confers resistance to lepidopteran pests such as bollworms. This paper examines Bt cotton performance with reference to transgene expression in plants cultivated under farmers conditions. Leaf and bolls samples from 940 plants were collected at 70 and 120 days after sowing (DAS) from 560 randomly selected households located in 19 districts concentrated in Punjab’s cotton belt. Qualitative analysis of these samples using immunoblot strip testing showed that 35% samples were not synthesizing Cry1Ac protein up to a detectable limit, and none of them was synthesizing the Cry2Ab protein. The quantitative profiling of transgene expression in leaves collected at 70 DAS showed that 59%, 30% and 8% samples are synthesizing toxin below 1, 2 and 3 ug/g of fresh tissue weight, respectively, while expression in the leaves of same plants at 120 DAS was below 1, 2 and 3 ug/g in 74%, 21% and 4% of the samples respectively. The expression level was lower in boll samples as compared to leaf samples with 82% and 79% samples having toxin less than 1ug/g at 70 and 120 DAS respectively. Correlating the expression data with temperature and humidity data collected at the field sites showed a positive and negative relation with humidity and temperature respectively. The conclusion from these results is that there are temporal, meteorological, and other factors affecting expression of the Bt transgene in farmers’ fields and these factors may result in ineffective resistance to lepidopteran pests. Ineffective resistance, in turn, may contribute to both crop losses for farmers and natural selection in favour of lepidopteran resistance to the toxic Bt proteins. This further suggests that the continued proliferation of unapproved and ineffective Bt cotton in Pakistan may have significant ecological, environmental and economic consequences.