| Scope and method of study. Characteristics other than mature height contribute to competitive ability of wheat, but the literature has not identified any other useful traits. Twenty-four winter wheat cultivars were seeded with and without jointed goatgrass (Aegilops cylindrica Host.) in five environments, 1999--2001. Wheat stand density, forage yield, height at Zadocks 32, 37, and 91, spike density, and yield were measured. Additionally, mature height, spike density, spikelet production, and spikelet density of jointed goatgrass were measured. An Oklahoma State University sensor was used to record incident and reflected wavelengths from the canopy of the 24 winter wheat cultivars grown with and without jointed goatgrass, 1999--2001. Normalized difference vegetative index (NDVI) was calculated. The introduction of imazamox tolerant winter wheat has increased interest in jointed goatgrass-winter wheat hybrids [Aegilotriticum sanctiandreae (Degen) Soo]. However, little is known about such hybrids in Oklahoma. Hybrid plants were collected from central Oklahoma, 2000 to 2002, for characterization and germination.;Findings and conclusions. Yields of the 24 wheat cultivars, at four environments were not affected by jointed goatgrass competition. Cultivars varied substantially in their ability to suppress jointed goatgrass spikelet production. Wheat stand density varied greatly and appeared to be related to competitive ability. Wheat forage production, height at Zadocks 32 and 91, and spike density were minor factors in suppressing jointed goatgrass spikelet production. Wheat height at Zadocks 37 was inversely related and wheat yield was variably related to jointed goatgrass spikelet production. NDVI was useful in estimating spike density, spikelet production, and spikelet density of jointed goatgrass, as well as estimating stand density and forage yield of the wheat cultivars grown without jointed goatgrass. NDVI was variable in estimating wheat height at Zadocks 32, 37, and 91, wheat spike density, and wheat yield. When the published morphological characteristics of the 24 wheat cultivars were considered, estimations improved. When certain stress factors such as plant diseases and late season drought were absent, correlations approached 0.9. Hybrid plants varied in mature height and spike length. Hybrid spike color was darker than mature wheat spike color and mature hybrid spikes disarticulated intact, unlike jointed goatgrass. Wheat cultivars varied in hybrid production ability. |
