@conference{1,
abstract = "Background
Since the commercial release of Bt cotton the issue of seed purity in producers' fields has been little addressed and in an unbalanced way when it was. It is well documented that the loss of purity in conventional seeds has endangered the continuation of organic cotton production. However, studies are rare on the purity of Bt-cotton seeds despite its implications on the effectiveness and sustainability of their use.
This communication compensates for the mentioned lack of literature by analyzing data collected in 2015 in Burkina Faso, namely results of ELISA tests on samples of seeds from 646 fields grown with conventional or Bt varieties. 
Results
According to the conservative criteria retained to declare the presence of Bt gene (more than 10% and 90% of controlled seeds for conventional and Bt variety, respectively), seed purity was very questionable for both types of varieties. For the conventional variety, the presence of Bt gene was observed on 63.6 and 59.3% of samples for Cry1Ac and Cry2Ab, respectively. Only 29.3% of samples corresponded to pure conventional seeds while 52.2% were double Bt seeds. Conversely, for the Bt variety, the presence of Bt gene was observed on 59.6 and 53.6% of samples for Cry1Ac and Cry2Ab, respectively. Actually BG2 seeds with both Bt genes were found in 40.4% of samples against 27.2% of samples of actually conventional seeds while the remaining of 32.4% of samples corresponded to single Bt gene seeds.
Two factors affected the severe lack of seed purity. As regard to conventional seeds, it clearly resulted from a phenomenon of contamination, indicative of a failure in adjusting the seed production scheme to the use of Bt-cotton. With regard to the Bt variety, the lack of purity of the original seeds provided to Burkina Faso accounted and should even be the major factor.
The observed lack of seed purity is a threat to the initiative of organic cotton production, albeit a very minor production mode in the country. It also calls upon the effectiveness and furthermore the sustainability of Bt cotton to control target pests. 
Conclusion
Our results show the extent of purity loss when no especial attention is paid to the preservation of seed purity. Pure conventional seeds could totally vanish while Bt seeds become a combination of seeds of various types encompassing or not the expected Bt genes.
Any country willing to embark the use of Bt cotton, or to resume this use like Burkina Faso, must previously adjust its seed production scheme and enforce its operation. This is a condition to preserve pure seeds both to enable the launch or the continuation of identity-cotton production and to ensure a sustainable effectiveness of Bt-cotton.
",
author = "Larbouga BOURGOU, Ester KARGOUGOU, Mahamadou SAWADOGO, Michel FOK",
booktitle = "7th World Cotton Research Conference",
title = "Status and implications of seed purity seven years after Bt cotton use in Burkina Faso",
year = "2020"
}