Inheritance of sulfonylurea resistance in Monochoria vaginalis

The inheritance of sulfonylurea (SU) resistance in Monochoria vaginalis was investigated based on the bensulfuron-methyl response phenotypes of F-1 plants between SU-resistant (R) and -susceptible (S) and segregation analysis in F-2 progenies. Differences of SU resistance between SU-R biotypes and F-1 plants at the recommended field dose were also investigated by comparing shoot dry weight. All F-1 plants survived the treatment with 25 g a.i. ha(-1) bensulfuron-methyl, one-third of the recommended field dose, and showed similar responses to SU-R plants. Conversely, all F-1 plants died or showed extreme necrosis at 225 g a.i. ha(-1), three times the recommended field dose, as SU-S plants. F-2 plants were classified as either R or S phenotype. Segregation for resistance to bensulfuron-methyl in F-2 families did not differ from the expected 3:1 (R:S) ratio at 25 g a.i. ha(-1). At 225 g a.i. ha(-1), the F-2 families segregated in a 1:3 (R:S) ratio. These results suggest that SU resistance in M. vaginalis is controlled by a single nuclear allele with resistance being dominant at low dose and susceptibility dominant at high dose. Moreover, F-1 plants died or were extremely injured after application of bensulfuron-methyl at the recommended field dose, although SU-R biotypes grew normally.