Effect of Spacing and Refuge Crops on Gene Transfer of NptII Gene from Bt cotton to Soil Bacteria and on Seed Cotton Yield

The proportion of bacteria resistant to kanamycin from Bt and non Bt cotton (nBt) cotton crop soil at 0.65m spacing was higher than crop soil samples from 0.35m spacing. nptII specific PCR total bacteria DNA samples from Bt cotton soil were negative confirming the presence of indigenous kanamycin resistant soil bacteria. Bt seed cotton yield in presence of 50% refuge was higher when sown at spacings of 0.65m than at 0.35m. In presence of 50% refuge a 94% increase in Bt seed cotton yield was obtained. The presence of 50% nBt refuge increased the seed cotton yield of Bt cotton plants and; did not cause horizontal gene transfer of the nptII gene to soil bacteria.