The present invention is directed to plants having increased tolerance to an imidazolinone herbicide. More particularly, the present invention includes rice plants containing at least one variant AHAS nucleic acid such as an imidazolinone tolerant IMINTA 1, 4 or 5 lines comprising an alanine to threonine substitution as compared to the wild-type AHAS. The present invention also includes seeds produced by these rice plants and methods of controlling weeds in the vicinity of these rice plants.