Kansas and North Dakota kochia populations identified as chlorsulfuron
resistant (R) contained 20 and 30% susceptible (S) plants, respective
ly. Biotypes that were chlorsulfuron R or S were selected from each fi
eld R or S collection and selfed through three generations in the gree
nhouse. Chlorsulfuron at 7.6 and 17.8 g ai/ha suppressed shoot biomass
of the Kansas and North Dakota R biotypes by 50%, respectively, which
was a 30- and 105-fold greater dose than that required to reduce the
respective S biotypes growth 50%. The R and S kochia biotypes are dipl
oid with 2N = 18 chromosomes. Chlorsulfuron resistance is inherited in
kochia as a dominant trait controlled by a single nuclear gene. Thus,
the resistance trait can be spread by seed and pollen.