(ISAAA, 2006). A soja geneticamente modificada resistente ao glifosato (GM RR ) foi obtida pela introdução, juntamente com a região t-DNA e o gene marcador de seleção, de gene correspondente à enzima 5-enolpiruvilchiquimato-3-fosfato sintase (EPSPS, E.C. 2.5.1.19, CP4), enzima da via de chiquimato, resistente ao glifosato, mantendo ativa a via biossintética de aminoácidos aromáticos (BUSSE et al., 2001). O glifosato [N-(fosfonometil) glicina] age sobre a enzima EPSPS inibindo a via de síntese dos aminoácidos aromáticos essenciais, fenilalanina, triptofano e tirosina, os quais são precursores de outros produtos, como lignina, alcalóides, flavonóides e ácidos benzóicos (AMARANTE; SANTOS, 2002). A priori, a soja GM RR é tolerante ao glifosato por possuir uma isoforma da EPSPS resistente a essa molécula. Porém, é sabido que o glifosato será absorvido e metabolizado pela planta podendo alterar o metabolismo secundário, uma vez
AbstractThe use of Glyphosate is the best way to control weed growing when cultivating genetically modified soybean (GMRR) BRS 244 RR. However, there have been doubts about the safety of this herbicide use concerning its effects on the quality of grains and on the soil of Albaqualf cultivated GMRR soybean. Glyphosate and the metabolite aminomethylphosphonic acid (AMPA) residues can be present in the grains and affect the isoflavones concentration. Therefore, BRS 244 RR and BRS 154 soybeans with the following cultivated treatments were evaluated: T1 -soybean BRS 244 RR, without herbicide and hand-weeded at 28 days after planting (dap); T2 -soybean BRS 154, without herbicide and hand-weeded at 28 dap; T3 -soybean BRS 244 RR with one application of 960 g ai ha -1 of glyphosate at 28 dap; T4 -soybean BRS 244 RR, with two applications of 960 g ai ha -1 of glyphosate at 28 and 56 dap; T5 -soybean BRS 244 RR, with one application of 100 g ai ha -1 of imazethapyr at 28 dap; and T6 -soybean BRS 154 with one application of 100 g ai ha -1 of imazethapyr at 28 dap. It was verified that the glyphosate application for weed control resulted in high levels of glyphosate and aminomethylphosphonic acid on the soil. The levels of isoflavone in the grains apparently were not affected by the glyphosate application, but the herbicide residues were higher than the current amount allowed by the legislation (10 mg.kg -1 ).
