BREEDING DURUM-WHEAT IN WESTERN CANADA - HISTORICAL TRENDS IN YIELD AND RELATED VARIABLES

Canadian durum wheat (Triticum turgidum L.) production is centred in t he Brown and Dark Brown soil zones, areas of limited rainfall. For mor e than 50 yr, lines have been evaluated in the multi-location Durum Co operative Test. Data from this lest, over the period 1947-1992, were a nalyzed with the objectives of determining the advances that have been made within the Canada Western Amber Durum (CWAD) wheat class and com paring yield-related variables of recently registered cultivars with t hose of earlier cultivars. Canadian-developed cultivars have increased yields about 0.81% yr(-1) relative to Hercules, or approximately 22.6 kg ha(-1) yr(-1). As kernel weight has remained unchanged, the geneti c yield increases have resulted entirely from an increase in the numbe r of kernels produced. Because kernel number is determined prior to, a nd during, anthesis, further yield increases may depend upon selection of genotypes that produce higher numbers of kernels, thereby increasi ng sink demand. While plant height and hectolitre weight have been dec reasing over time, neither variable was significantly (P < 0.05) corre lated with the yield increases that have taken place over the 29-yr pe riod. The selection pressure toward shorter cultivars may have involve d other agronomic advantages, such as decreased lodging. Days to matur ity did not change significantly over time and was not correlated with yield.