Glyphosate is the most used herbicide worldwide, and it is a relatively high use rate herbicide. It is a non-selective herbicide with a unique mode of action that is ideal for vegetation management in both agricultural and non-agricultural settings. Its use was more than doubled by the introduction of transgenic, glyphosate-resistant (GR) crops. Glyphosate is tightly bound by most soils, so its movement to surface and ground water is relatively little comparted to most other pesticides. It is readily degraded by many soil microbes, makings its environmental half-life relatively short. All of its phytotoxic effects are through inhibition of only 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS), but inhibition of this single enzyme of the shikimate pathway results in multiple effects, both upstream and downstream from EPSPS, including loss of plant defenses against pathogens. This does not occur in GR crops. Most degradation of glyphosate in plants and microbes is predominantly by a glyphosate oxidoreductase or to a lesser extent by a C-P lyase. Its effects on non-target plant species are generally less than that of many other herbicides, as it has a low propensity to drift and is inactivated by soil. Glyphosate can benefit GR crops by its activity on plant pathogens that are sensitive to glyphosate. On the other hand, glyphosate can adversely affect some microbes that are beneficial to agriculture, such as <i>Rhizobium</i> species, although GR crop yield data indicate that such an effect has been minor.<br/> <br/>

Overview of environmental fate of glyphosate and its effects on glyphosate-resistant crops

ACS Fall 2020 Virtual Meeting

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