PLANT PHYSIOLOGY , Vol 103, Issue 1 281-283, Copyright © 1993 by American Society of Plant Biologists
Lack of Cross-Resistance of Imazaquin-Resistant Xanthium strumarium Acetolactate Synthase to Flumetsulam and Chlorimuron
P. R. Schmitzer, R. J. Eilers and C. Cseke
DowElanco, P.O. Box 68955, Indianapolis, Indiana 46268-1053
Acetolactate synthase (ALS) was isolated from a field population of
cocklebur (Xanthium strumarium) that developed resistance to the herbicide
Scepter following three consecutive years of application. The active
ingredient of Scepter, imazaquin, gave an inhibitor concentration required
to produce 50% inhibition of the enzyme activity that was more than 300
times greater for the resistant enzyme than for the wild-type cocklebur
ALS. Tests with flumetsulam and chlorimuron show that the resistant ALS was
not cross-resistant to these two other classes of ALS inhibitors.
