Effects of genetically modified cotton (Bt cotton) on native and inoculated soil microorganisms.

摘要

Transgenic plants are considered to be of immense importance for sustainable agriculture. Many transgenic crops such as soybean, maize, canola and cotton containing economically useful and health related genes have been developed for longer shelf life, disease resistance, herbicide resistance, insect resistance and stress resistance such as to drought or nitrogen starvation and nutritional improvement. Transgenic cotton plants expressing Cry1Ac and Cry2Ab, from the soil bacterium Bacillus thuringiensis (Bt) provide an effective control of certain lepidopteran insects. However, little is known about the proteins below ground expression and potential benefits of transgenic plants. In the present study, effect of Bt cotton was studied on native and inoculated microorganisms in the rhizospheric soil under field as well as pot house conditions, respectively. Marginal increase in native microbial population of non-Bt cotton compared to Bt cotton after 45 days of sowing (DAS) was observed in two different varieties RCH 134 and MRC 6301 tested. However, after 90 DAS there was decrease in microbial population and it was almost similar both in the Bt and non-Bt cotton rhizosphere. Genetically marked strains of Azotobacter (A-2), Azospirillum (J-11-12) and phosphate solubilizing bacterium (BPL-2) established better in the rhizosphere of non-Bt cotton, var. RCH 134 under pot house conditions and their population was ten times higher after 30 DAS. Increase in plant height, plant biomass, N and P uptake due to inoculation was observed at recommended dose of fertilizers both in Bt as well as in non-Bt cotton.