BREEDING HARD RED SPRING WHEAT IN WESTERN CANADA - HISTORICAL TRENDS IN YIELD AND RELATED VARIABLES

The Western Bread Wheat Cooperative test and Central Bread Wheat Coope rative test are the bases of evaluation for cultivar registration in t he Canada Western Red Spring (CWRS) wheat class. Historical data from these tests were analyzed with the objectives of comparing grain-yield -related variables of recently registered cultivars with those of earl ier cultivars and determining the yield advances made within the CWRS wheat class. Canadian cultivars increased maximum yield potential appr oximately 6-9 kg ha(-1) yr(-1) during a 90-yr period. Yield potential of sawfly-resistant cultivars has been increasing at a rate of 11 kg h a(-1) yr(-1), although they consistently yielded less than the highest yielding hollow-stem cultivars. In general, the genetic yield increas es resulted from an increase in the number of kernels produced rather than an increase in kernel size. This suggests that bread wheat grown on the prairies has been sink limited during grain filling. Breeding e fforts focused on increasing Canadian production through the developme nt of numerous CWRS cultivars with specific traits (e.g., early maturi ty, disease resistance) to allow hard red spring wheat to be grown ove r a broad geographical range. Plant height, time to maturity, and hect olitre weight did not change significantly during the 1947-1992 period .