Roundup Ready® soybean gene concentrations in field soil aggregate size classes

Roundup Ready((R)) (RR) soybeans containing recombinant Agrobacterium spp. CP4 5-enol-pyruvyl-shikimate-3-phosphate synthase (cp4 epsps) genes tolerant to the herbicide glyphosate are extensively grown worldwide. The concentration of recombinant DNA from RR soybeans in soil aggregates was studied due to the possibility of genetic transformation of soil bacteria. This study used real-time PCR to examine the concentration of cp4 epsps in four field soil aggregate size classes (> 2000 mu m, 2000-500 mu m, 500-250 mu m and < 250 mu m). Aggregates over 2000 mu m in diameter had significantly greater gene concentrations than those with diameters under 2000 mu m. The > 2000 mu m fraction contained between 66.62% and 99.18% of total gene copies, although it only accounted for about 30.00% of the sampled soil. Aggregate formation may facilitate persistence of recombinant DNA.