Mesotrione: a new selective herbicide for use in maize

Mesotrione is a new herbicide being developed for the selective pre- and po st-emergence control of a wide range of broad-leaved and grass weeds in mai ze (Zea mays). It is a member of the benzoylcyclohexane-1,3-dione family of herbicides, which are chemically derived from a natural phytotoxin obtaine d from the Californian bottlebrush plant, Callistemon citrinus. The compoun d acts by competitive inhibition of the enzyme 4-hydroxyphenylpyruvate diox ygenase (HPPD), a component of the biochemical pathway that converts tyrosi ne to plastoquinone and alpha -tocopherol. Mesotrione is an extremely poten t inhibitor of HPPD from Arabidopsis thaliana, with a K-i value of c 6-18 p M. It is rapidly taken up by weed species following foliar application, and is distributed within the plants by both acropetal and basipetal movement. Maize is tolerant to mesotrione as a consequence of selective metabolism b y the crop plant. Slower uptake of mesotrione, relative to susceptible weed species, may also contribute to its utility as a selective herbicide for u se in maize. (C) 2001 Society of Chernical Industry.