Transgenic Bt cotton tissues have no apparent impact on soil microorganisms

Abstract

The impact of transgenic Bacillus thuringiensis (Bt) cotton residues on soil microorganism communities was investigated. Leaves of three different varieties of transgenic Bt cotton and their near-isogenic lines were placed in soil and the numbers of indigenous soil microorganisms were measured with cultivation-dependent approaches under laboratory conditions. The soil samples were collected after 7, 14, 21, 28, 56 and 84 days of incubation. Numbers of bacteria, actinomycetes and fungi in the soil were measured by counting colony forming units after incubation on appropriate medium. Overall, although there were differences in bacteria, actinomycetes and fungi population between soil amended with Bt and non-Bt cotton throughout the whole incubation in three experiments, these differences were transient and not persistent from one sampling stage to the next. These results suggest that Bt-transgenic cotton tissues have no apparent impact on soil microorganism population.