Effects of glyphosate in glyphosate-tolerant transgenic maize

Abstract

This proposal aims to financially complement a project partially supported by CNPq/Universal in progress, due to the interruption of laboratory activities for nutritional analysis of plants due to the pandemic situation. The original project objectives to analyze effects caused by the herbicide glyphosate on plant growth, plant mineral nutrition and plant metabolism of maize and on grain mineral nutrition, grain quality and grain yield of maize, and to evaluate the presence of herbicide residues in grains of glyphosate-tolerant transgenic maize under greenhouse and field conditions, in a continuation of studies that have been carried out by the research group. The experiments are being conducted for two consecutive years. In the field, the experiments are being conducted in three locations: Dracena and Jaboticabal, SP, and Guarapuava, PR; and in greenhouse, the experiments are being conducted in Jaboticabal, SP. The treatments are: (i) control without application of glyphosate; (ii) single application of glyphosate at 980 g a.e. ha-1 at 21 days after emergence (DAE); and (iii) sequential application of glyphosate at 520 + 980 g a.e. ha-1, at 14 and 28 DAE, respectively, both in greenhouse and in the field. A completely randomized design in greenhouse experiments and a randomized block design in field experiments are being used, both with 10 replicates. Plant height, stem diameter, number of leaves, contents of glyphosate, aminomethylphosphonic acid (AMPA), shikimic acid, phenylalanine, tyrosine and tryptophan, macro- and micronutrients, and gas exchanges are being evaluated in the greenhouse. In the field, these same evaluations are being carried out, as well as components of yield, productivity, contents of starch, total proteins and ethereal extract, macro- and micronutrients in the grains and contents of glyphosate and AMPA in grains. For the development of this project, partnerships were made with the University of Mississippi and UNESP of Botucatu (studies on metabolism and residues of glyphosate and AMPA) and with the UNESP of Dracena and Unicentro (field experiments). Metabolic studies and advanced studies on the quality of grains and residues of glyphosate and AMPA in grains, as well as the development of field experiments in different locations, are the main innovations of this project in relation to the previous one. It is expected to confirm that there is no change in mineral nutrition, photosynthesis and metabolism of the shikimic acid route of maize plants to the point of affecting their growth, productivity and grain quality; besides elucidating what occurs with glyphosate in the plant and if there is or is not the accumulation of residues of glyphosate and AMPA in grains in order to verify the safety of consumption of maize grains. In addition, this project will support the orientation of students of scientific initiation and doctorate in Agronomy (Plant Production) in UNESP of Jaboticabal. (AU)