Impact of transgenic cottons expressing cry1Ac on soil biological attributes

Three transgenic Bt cotton hybrids (RCH-2 Bt, Bunny Bt and NHH 44 Bt) expressing cry1Ac gene were evaluated for their effects on soil biological, microbiological and diversity attributes at 0-15 cm and 15-30 cm soil depth under field conditions. At both soil depths, soil respiration rate and fluorescein diacetate hydrolysis were the highest in the soil under Bt cotton grown followed by non-Bt soil, and by the control bulk soil, indicating no adverse effects of Bt cotton on soil microbial activity. Urease and dehydrogenase activities, reflecting potentially available N and the oxidative metabolism in soil, respectively, also increased in the sequence no-crop variant < non-Bt soil < soil under Bt cotton at both soil depths. A similar trend was found with the soil microbial biomass carbon, microbial population and microbial diversity indices. These results suggest that cultivation of Bt cotton expressing cry1Ac gene may not pose ecological or environmental risk.