Effects of repeated cultivation of transgenic Bt cotton on functional bacterial populations in rhizosphere soil

Abstract

The impact of multiple-year (0-5 years) cultivation of transgenic Bacillus thuringiensis (Bt) cotton on the functional bacterial populations in rhizosphere soil was investigated. The transgenic Bt ? CpTI cotton line SGK321 and a non-Bt cotton line Shiyuan321 were planted in four fields in which Bt cotton had been continuously cultivated for 0, 1, 3, and 5 years. Rhizosphere soil samples were collected at the seedling, squaring, flower and boll, and boll-opening stages of cotton. Numbers of bacteria involved in nitrogen-fixing, organic phosphate-dissolving, inorganic phosphate-dissolving, and potassium-dissolving were measured with cultivation-dependent approaches. The data presented here showed no consistent statistically significant differences in the numbers of different groups of functional bacteria between rhizosphere soil of Bt and non-Bt cotton in the same field, and no obvious trends in the numbers of the various group of functional bacteria with the increasing duration of Bt cotton cultivation. These studies suggest that multiple-year cultivation of transgenic Bt cotton may not affect the functional bacterial populations in rhizosphere soil.

Impact of transgenic cottons expressing cry1Ac on soil biological attributes

“…Higher microbial populations in transgenic cotton grown soil were also reported by several workers (Shen et al 2006, Kapur et al 2010. Hu et al (2009) based on their multipleyear cultivation showed that transgenic Bt cotton was not found to affect the rhizosphere functional bacterial population. Saxena and Stotzky (2001) did not observe any significant differences in the numbers of culturable bacteria, actinomycetes, and fungi in the rhizosphere of transgenic Bt and non-transgenic maize.…”

Risk assessment strategies for transgenic plants

“…In a study, Bt cotton producing cry protein had been cultivated for 5 years and the crop residues were incorporated into soil following post-harvest tillage. The authors concluded that multiple year cultivation of transgenic cotton may not affect the bacterial populations in soil (Hu et al 2009). Although Bt maize is the most studied GM crop, there is still a lack of continuity between studies at the laboratory and field scales.…”

Soil Fertility status of Bt cotton Cultivated fields and other Soils of Khammam region in relation with available macro, micro nutrients and Microbial count

“…Some studies have shown that repeated and large-scale use of transgenic Bt crops could lead to the accumulation and persistence of Bt proteins in soil [8,9,19,20]. Saxena and Stotzky (2002) showed that the toxin released in root exudates and from the biomass of Bt corn rapidly binds to surface-active particles in soil and remains larvicidal activity for at least 180 days [19,20,21]. The present study focused on the fertility status of Bt cotton soils compared with other crop cultivated soils in the region of Khammam, Andhra Pradesh, India.…”