Análises bioquímicas de soja convencional e transgênica, resistente ao glifosato relacionadas ao conteúdo de lignina e chiquimato

Abstract

The present thesis is composed by four independent studies which were described as chapters. The general goal was to conduct a comparative study between GR soybean cultivars (resistant to glyphosate) and their parental cultivars with respect to the lignification and shikimate accumulation. In the first chapter, the contents of shikimate and lignin in plants of transgenic and conventional soybean at two stages of development, submitted or not to the herbicide glyphosate were evaluated. Analyses performed at V3 stage indicated an accumulation of shikimate in the conventional cultivar. In turn, the conventional cultivar accumulated shikimate after herbicide application, indicating sensitivity to the glyphosate. In the R7 stage was possible to note an increase of lignification in plants, both in stem and leaves. In these plants, glyphosate reduced dry weight and lignification of transgenic cultivars (BRS 242 RR). The goal of the second study was to evaluate the effects of glyphosate on accumulation of shikimate and activity of shikimate dehydrogenase (SDH) in conventional and transgenic soybean leaves, submitted to the herbicide glyphosate. The analyses were done immediately after spraying (zero time) and up to five days. In leaves of the conventional cultivar, treated with glyphosate, was noted increases of shikimate accumulation and activity of SDH, indicating that the action of glyphosate had significant effects on shikimate pathway. Accumulation of shikimate was not observed in glyphosate-resistant cultivar and, in general, the enzyme activity was not affected by the herbicide. The third chapter aims to determine the lignin concentration and composition of the major monolignol in the seed coat of RR soybeans and conventional, in order to determine whether the genetically modified soybean resistant to glyphosate, shows variation in the levels of polymer in the seed coats, compared with its parental cultivar. In this study, the lignin content in the seed coat varied in only one of six contrasts tested. Finally, the fourth chapter brings the chromatographic analysis of six different contrasts, each consisting of a contrast transgenic crops and their respective parent cultivar conventional or not subjected to soaking in 0.6% solution of glyphosate. The accumulation of shikimate was detected only in conventional cultivars, in which the seeds were previously soaked in 0.6% solution of glyphosate. The results showed that the detection of shikimate by chromatographic method can be used as a quick and accurate in differentiating glyphosate-resistant soybeans for soy.