The objective of this experiment consisted in simulation in vitro of the transgenic soybean tolerant to glyphosate through explant cultivation in culture medium containing aromatic amino acids. The effects of glyphosate on soybean (Glycine max (L.) Merrill) were evaluated in seeds harvested from explants of cv UFV-16. The soybean explants were cultivated in liquid medium culture with pH about 5.0. Each explant consisted of one fruit completely expanded, containing two seeds of 100 mg approximately, and connected to a stem segment of 45 mm length. The explants were submitted to the following treatments: A = glutamine (Gln); B = Gln + phenylalanine (Phe) + tyrosine (Try) + tryptophan (Trp); C = Gln + glyphosate; D = Gln + Phe + Tyr + Trp + glyphosate. The experiment was conducted under irradiance of 80 mmol-2s-1 at 25o for 204 hours. The treatments with aromatic amino acids and glutamine avoided the herbicide effect on seed fresh and dried weights and had no effect on their biochemical constituents (proteins, oil, fatty acids, carbohydrates and chlorophylls). Thus, an exogenous supplementation of aromatic amino acids eliminates phytotoxic effects of glyphosate on soybean explants. Therefore, it was developed an in vitro system that allows to study the mode of action and the metabolism of glyphosate in soybean seeds, since the explants behaved in a similar manner as the transgenic soybean unsusceptible to the herbicide.
Glycine max; in vitro culture; shikimate pathway; aromatic amino acids; seed composition