Glyphosate Stimulates the Accumulation of N-Compounds, Grain Yield and Seed Vigor in Glyphosate-Resistant Soybean

Abstract

Glyphosate-resistant (GR) soybean is widely used in agriculture, however, plants exposed to herbicide show physiological changes. This study investigated the effect of treatments with glyphosate on the metabolism of N compounds, crop yield and physiological quality of seeds in GR soybean. The plants were grown in field experiment, located in the city of Selvíria, MS, Brazil. Glyphosate was applied postemergence at V 4 crop stage in a dose-response, including four rates (0; 360; 720 and 1440 g e. a. ha -1 ) with four replicates. Crop yield, physiological and biochemical features were determined. The results revealed previously unreported stimulant effects of glyphosate on GR soybean plants. Glyphosate changed the ureide shape in leaves, but did not change the concentration of total ureides, indicating maintenance of biological nitrogen fixation in plants exposed to herbicide. Amino acids concentration increased in plants submitted to higher doses. GR soybean showed higher crop yield and seed vigor with increased glyphosate doses. The results of this study indicate that glyphosate does not cause stress to the plant; however, it modulates a distinct response in plant development due to the protective gene inserted. This study can serve as a matrix for additional studies in order to seek clarification of responses of resistant/tolerant plants to glyphosate.

Lack of effects of glyphosate and glufosinate on growth, mineral content, and yield of glyphosate- and glufosinate-resistant maize

“…Our results agree with the findings of Williams et al (2015) that glyphosate has no significant effect on yield of GR maize, although they found a slight increase in yield. Others have found no effect or a slight increase in yield from glyphosate treatment of GR soybean (Silva et al 2018). Non-toxic doses of glyphosate sometimes cause stimulation of growth, including yield, a hormesis effect (Brito et al 2018).…”

“…Total nitrogen was then determined by titration with sulphuric acid, using boric acid as indicator. The N content was multiplied by 6.5 (1% N corresponds to 6.25 g protein) to calculate the crude protein content, according to Silva et al (2005).…”

Glyphosate Resistance Technology Has Minimal or No Effect on Maize Mineral Content and Yield

“…The previously reported increased yield (8.3% increase in harvested kernel mass) in glyphosate-treated GR maize in this study in Urbana 35 may be a hormetic response to glyphosate, as hormetic responses to glyphosate are common. 41 Indeed, Silva et al 42 recently reported that glyphosate at 1.44 kg ha −1 increased yield of GR soybean, independently of its effects on weed control. Because glyphosate is about 50-fold less effective on GR crops than on susceptible isogenic cultivars, 5 one might expect that the hormetic dose for GR crops to be much higher than a hormetic dose for a glyphosate-sensitive crop (about 20 g ha −1 for maize).…”

Is Mineral Nutrition of Glyphosate-resistant Crops Altered by Glyphosate Treatment?

“…The general increase in yield with time is about the same before and after adoption of GR versions of these crops. Indeed, the recent multiyear, multisite studies of GR soybean and maize have reported either no effect of glyphosate on yield, or a small increase at some sites in the upper Midwest of the US and in Brazil (Kandel et al, 2015Reddy et al, 2018;Silva et al, 2018: Williams et al, 2014.…”