Solanum ptycanthum Resistance to Acetolactate Synthase Inhibitors

Dean S. Volenberg, David E. Stoltenberg, and Chris M. Boerboom

Solanum ptycanthum (eastern black nightshade) plants putatively resistant to acetolactate synthase (ALS) inhibitors were identified in a Wisconsin Glycine max (soybean) field in 1999. Three- to four-leaf stage S. ptycanthum plants in the greenhouse were 150, 120, and 5.9-fold resistant to imazethapyr, imazamox, and primisulfuron, respectively, compared with susceptible plants. In vivo ALS was 170- and less than 20-fold resistant to imazethapyr and primisulfuron, respectively. These results suggested that the S. ptycanthum accession was highly resistant to imazethapyr and imazamox, and that resistance was associated with insensitive ALS. This is the first confirmed occurrence worldwide of S. ptycanthum resistance to ALS inhibitors.

Weed Sci. 48:399-401 (2000)