Monogenic dominant sulfonylurea resistance in sugarbeet from somatic cell selection

Injury to sugarbeet, Beta vulgaris L., from sulfonylurea herbicide residues from preceding cropping years has kindled interest in developing resistant cultivars. This study was conducted to obtain chlorsulfuron (2-chloro-N-[[(4-methoxy-6-methyl-1,3,5-triazin-2-yl)amino]carbonyl]benzenesulfonamide) resistance from cell cultures and to determine its inheritance and magnitude. Utilizing annual diploid sugarbeet clone REL-1, dispersed suspension cultures were initiated from callus induced on leaf disk cultured on a modified Murashige and Skoog (MS) agar medium + 1.0 mg L⁻¹ N⁶-benzyladenine (BA) and placed in the liquid form of the same medium. Unmutagenized cell clusters were plated on solid medium containing 2.8 nM chlorsulfuron in MS + 1.0 mg L⁻¹ BA. A single colony arose, from which shoots were regenerated. Shoots were resistant to 28 nM chlorsulfuron, a concentration that killed similar shoots of REL-1. Resistance (designated Sur) was inherited as a monogenic dominant. In vitro shoot resistance to chlorsulfuron was 300 to 1000-fold greater than in REL-1. Resistance was also expressed in leaf disk expansion in vitro with MS + 1.0 mg L⁻¹ BA. Acknowledgement is made to the Michigan Agricultural Experiment Station for its support of this research.