No herbicide with a novel molecular site of action (SOA) has been introduced since the 1980s. Since then, the widespread evolution of resistance of weeds to most commercial herbicides has greatly increased the need for herbicides with new SOAs. Two unreported strategies for discovery of new herbicide SOAs are discussed. Some primary metabolism intermediates are phytotoxic (e.g., protoporphyrin IX, and sphingoid bases), and, because of this, the in vivo concentrations of these compounds are kept very low in plants by tight metabolic regulation. Determination of all primary metabolite and primary metabolite derivative phytotoxicities and pool sizes could identify herbicide targets with greater potential than others. The second approach is to identify potential SOAs with very low in vivo enzyme levels. We know that higher numbers of enzyme molecules for a SOA requires more herbicide to kill a plant. For example, plants with high levels of 5-enolpyruvylshikimate-3-phosphate synthase are resistant glyphosate. Modern proteomic methods can identify low enzyme level SOAs for biorational herbicide discovery. These two approaches might be helpful in discovery of herbicides that can be used effectively at lower doses.

Discovery of new herbicide modes of action by quantification of plant primary metabolite and enzyme pools

2019 Fall National Meeting

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