Thirteen selections of kochia(Kochia scoparia(L.) Schrad.), self-pollinated for four generations, varied in response to (2,4-dichlorophenoxy)acetic acid (2,4-D) and 3,6-dichloro-o-anisic acid (dicamba). The most susceptible selection was injured more by 0.35 kg/ha of the dimethylamine salt of 2,4-D than the most tolerant by 0.70 kg/ha based on visual injury rating, growth in plant diameter relative to untreated controls, and seed production. The 0.28 kg/ha rate of dicamba injured the most susceptible selection as much as 0.54 kg/ha injured the most tolerant based on visual injury rating and change in plant diameter. Plant size and maturity influenced the response of kochia to herbicides, but the differences in response among selections could not be explained by variations in size or maturity. All kochia selections were tolerant to 4-amino-3,5,6-trichloropicolinic acid (picloram) at 4.28 kg/ha.
Floral induction in kochia(Kochia scoparia(L.) Schrad.) was influenced more by light period and temperature than by soil fertility or soil moisture. Floral induction occurred when the light period per 24-hr cycle was shorter than a critical length. However, the critical duration of light per 24-hr cycle at which floral induction occurred varied from about 13 to 15 hr among kochia selections. The time from emergence to flowering varied from 57 to 100 days. The kochia selection from New Mexico required a shorter light period and a longer time after emergence for floral induction than did selections from North Dakota, South Dakota, and Minnesota. Kochia selections from the latter three states varied greatly in flowering date.
Thirty-six collections of foxtail barley(Hordeum jubatumL.) from North Dakota, South Dakota, Minnesota, Wisconsin, and Montana varied in susceptibility to 1-(2-methylcyclohexyl)-3-phenylurea (siduron) as determined from radicle elongation of treated seeds. Data from F2seedlings of crosses between tolerant and susceptible selections indicated that three complementary dominant factors control the inheritance of siduron tolerance in foxtail barley. Evolution of siduron-tolerant foxtail barley could occur from selection pressure.
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