Competitive ability of western Canadian spring wheat cultivars in a model weed system

Economic and social pressures are spurring the study of alternate weed management strategies such as the development of competitive crop cultivars, capable of being used under an integrated management plan. The primary objective of this research was to determine whether western Canadian spring wheat (Triticum spp.) cultivars differ in their ability to compete against model weeds and whether those differences were expressed when challenged with wild weeds. A total of 71 wheat cultivars were grown in the absence or presence of simulated [cultivated oat (Avena sativa L.) and oriental mustard (Brassica juncea L.)] or natural [wild oat (Avena fatua L.)] weed competition conditions. Significant (p = 0.01) weed by cultivar interactions involving changes in yield cultivar rank were detected, indicating that the cultivars responded differently to competition. A small minority of cultivars such as Glenlea, CDC Rama, Genesis, AC Taber, AC Vista, Plenty, Napoleon, and BW652 had high-yield potential coupled with yield maintenance under weed pressure. The competitive ability advantage appeared to be associated with plant height or tillers per square meter as well as shorter vernalization requirement combined with photoperiod sensitivity. These outlier cultivar differences could be exploited in breeding new widely adapted varieties for scenarios where reduced herbicide weed control is desired, including situations where herbicide resistance limits chemical options. Cultivars with differing competitive ability under model weed conditions maintained their ranking when challenged by natural weed infestations. This suggests that selecting competitive spring wheat cultivars using a repeatable protocol based on model weeds is realistic.