Agronomic changes from 58 years of genetic improvement of short-season soybean cultivars in Canada

Yield progress of short-season soybean [Glycine mar (L,) Merr.] cultivars in Canada has been approximately 0.5% per year since the early 1930s. Our objective was to identify changes in agronomic traits associated with yield increase within a selection of historical cultivars. Where applicable, we measured phenotypic stability of these traits. At Ottawa, ON, we grew 14 cultivars, representing seven decades of breeding and selection (1934-1992), in a randomized complete block design with four replicates, across 6 yr. Data were collected on seed yield, seed weight, plant height, plant population, lodging susceptibility, and foliar disease symptoms. Seed number per plant was calculated from yield, seed weight, and plant population, Seed protein and oil concentration were measured. The increase in seed yield with year of release was associated with a significant increase in the number of seeds produced per plant. There was no relationship between seed yield and seed weight. A significant decrease in seed protein concentration with year of release was offset by a significant increase in seed oil concentration. Newer cultivars were more phenotypically stable for plant height than older cultivars, Modern cultivars were more efficient at establishing, supporting, and filling seeds on a per-plant basis than older cultivars.