Metabolic Resistance to HPPD‐Inhibiting Herbicides in Dioecious Amaranthus Species

This chapter discusses the current state of knowledge regarding the occurrences of and metabolic basis for resistance to various 4-hydroxyphenylpyruvate dioxygenase (HPPD)-inhibiting herbicides in dioecious Amaranthus spp., including descriptions of molecular genetic, biochemical, and physiological aspects of resistance. Our goals are to (a) provide a comprehensive summary of current knowledge regarding metabolic resistance mechanisms to HPPD-inhibiting herbicides in weeds and (b) establish a framework for future detailed studies toward a better understanding of metabolic pathways, enzymes, and genes conferring resistance to HPPD-inhibiting herbicides in the dioecious Amaranthus spp. Ultimately, this knowledge can be applied toward devising effective and integrated strategies for managing weedy Amaranthus spp., including the development of resistance-breaking herbicide chemistries.