Herbicide-tolerant mutants of corn

Abstract

Eight imidazolinone herbicide resistant corn cell lines were obtained from in vitro cell culture selections. Plants were regenerated from five of the lines and resistant progeny obtained from four. Of the four, one line showed cross resistance to a sulfonylurea herbicide (class A), while three lines were resistant only to imidazolinones (class B). The class A line and one class B line were characterized in detail. Line XA17 possessed a single semidominant gene for resistance and plants homozygous for the trait showed 300-fold resistance to imazaquin and 100-fold resistance to chlorsulfuron. Resistance was due to decreased herbicide sensitivity of acetohydroxy acid synthase (AHAS), the common site of action of the imidazolinone and sulfonylurea herbicides. Resistance was stable following four to six backcrosses to corn inbred lines. Line QJ22 (class B) plants homozygous for tolerance showed 30-fold resistance to imazethapyr and no resistance to imazethapyr and no resistance to chlorsulfuron. The biochemical mechanism of resistance for line QJ22 is presently not clear.Key words: corn, maize, herbicide tolerance, acetohydroxy acid synthase, imidazolinone, sulfonylurea.