The contribution of attributes in the seed, seedling, and mature plant phases to barley (Hordeum vulgare) cultivar competitiveness against weeds

Barley is an economically important crop in western Canada and is considered competitive, although cultivar competitiveness varies. Utilization of crop and cultivar competitive ability is an integrated weed management strategy that has no cost for producers. Adoption of cultivar competitive ability by producers requires a ranking system for cultivar competitive ability, that is not currently in place.; A Seed-Leaf-Height (SLH) framework was adapted from ecology to examine the relationship of attributes in the seed (S), seedling, (L), and mature plant (H) phases to barley cultivar competitive ability. Major phases and sub-phases are defined by morphological or physiological characteristics relevant to barley. Attributes were examined within this framework to determine their relationship to barley cultivar competitive ability.; The two aspects of competitive ability, ability to withstand competition (AWC) and ability to compete (AC), had a sufficiently strong relationship that breeding for one should increase the other for some cultivars. Highly- and poorly-competitive cultivars had consistent competitive rankings among site-years, while intermediately-competitive cultivars were less consistent. Consistency of competitive rank simplifies producer selection of competitive cultivars and breeding efforts to improve barley cultivar competitive ability.; The SLH framework allowed us to see connections between measurements taken at different stages. Seed, seedling, and mature plant vigour are all thought to contribute to barley cultivar competitive ability. However, seed vigour is not well-defined from a competitive ability perspective, and thus, its contribution to increased competitive ability in later stages is unclear. Some attribute measurements (e.g. height) may be taken from the early L phase (after emergence) well into the H phase (at harvest). This research indicated the importance of measuring attributes earlier, rather than later, and suggested a dependence of later measurements on earlier ones. Competition research incorporating attribute measurements from later developmental stages has not considered the dependence of these later measurements on measurements from earlier stages and could profitably do so (Jordan 1993).; Using information from this thesis, breeders can breed for increased cultivar competitive ability and rank the cultivars. Weed research can integrate relative differences in cultivar competitive ability into crop-weed competition models (e.g. herbicide rate) and agronomic research (e.g. seeding rate) into improving cultivar, and hence, crop competitive ability. Extension personnel can use this information in decision support systems (e.g. herbicide rate) to provide information to producers. Producers can then use this information select more competitive cultivars for their cropping systems. This value-added information chain can reduce increase the effectiveness of cultivar competitive ability as an integrated weed management tool and enhance the economic and environmental sustainability of agriculture. (Abstract shortened by UMI.)...