Evaluation of High‐Yielding Canadian Soybean Cultivars Suited to Japanese Growing Conditions

Core Ideas Five Canadian soybean cultivars achieved high yields in Hokkaido, northern Japan, in screening tests. OAC Dorado soybean produced a significantly greater yield than a Hokkaido's leading cultivar. OAC Dorado soybean had six characteristics that were distinct from the Hokkaido cultivars. OAC Dorado soybean is an important germplasm for high‐yield breeding. The broadening of genetic diversity is essential to improving soybean [Glycine max (L.) Merr.] seed yields, and exotic germplasms can be a source of new alleles that improve yield. The stem termination habit is an important trait affecting seed yield in soybean, and this habit can be used to classify soybean into indeterminate, semi‐determinate, and determinate phenotypes. The genetic background and environment determine whether indeterminate phenotypes have a higher yield than determinate phenotypes. Most soybean cultivars developed in high latitude countries such as Canada, Switzerland, and Poland have an indeterminate growth habit, but this is not found in any of the commercial Japanese cultivars. This study investigated high‐yielding Canadian soybean cultivars growing in Hokkaido, northern Japan. Five Canadian cultivars, Haroson, RCAT Angora, Block, RCAT Alliance, and OAC Dorado, produced significantly greater than Hokkaido's leading cultivar Yukihomare in the preliminary screening tests. OAC Dorado also produced a significantly greater yield than Yukihomare in the trials (116%). OAC Dorado had six characteristics that were distinct from the Hokkaido cultivars: an indeterminate growth habit; high pod number, especially on branches; high seed number per pod; long reproductive period; low protein content; and short lower internodes. Our findings indicate that OAC Dorado is an important germplasm for high‐yield breeding and suggest that it may be possible to breed a high‐yielding cultivar with an indeterminate growth habit in Hokkaido.