Experiments were conducted to determine the productivity and the competitive ability of a large crabgrass accession (PW2) resistant to acetyl-coenzyme A carboxylase (ACCase) inhibitors relative to a susceptible accession (A310). Under noncompetitive conditions in the field, shoot dry biomass and plant height over time were similar for the two accessions. Leaf area was slightly greater for A310 than for PW2. The instantaneous relative growth rate was similar for the accessions. The instantaneous net assimilation rate was slightly greater for A310 than for PW2; however, the instantaneous leaf area ratio was slightly greater for PW2 than for A310. At maturity, the seed yield was similar for the accessions. The inter-accession competitive ability of PW2 and A310 plants in the field was similar, based on shoot dry biomass or seed yield. In the greenhouse, interspecific competitive ability of the accessions with corn was similar, based on shoot dry biomass or seed yield. These results suggest that resistance to ACCase inhibitors is not associated with reduced fitness of the PW2 accession.
