Genotype x region interaction for two-row barley yield in Canada

Barley (Hordeum vulgare L.) breeding programs recognize eastern and western Canada as separate target regions, but the extent of local adaptation to regions and subregions within them has not been studied. Genotype x region and subregion interactions were estimated in 145 lines from the two-row barley cross Harrington/TR306 in 22 trials in 1992-1993, The trials were grouped into five subregions (Maritimes-Quebec, Ontario, Manitoba-North Dakota, Saskatchewan, and Alberta) and two regions (eastern Canada and western Canada plus North Dakota). Variance components were estimated by a model in which the genotype x location (sigma(GL)(2)) variance was subdivided into a genotype x region (or subregion) variance ((TGS)) and a within-region or -subregion sigma(GL)(2). NO sigma(GS)(2) was observed within the eastern or western regions, and genotypic correlations across subregions within regions approached 1.0. Significant sigma(GS)(2) was observed for eastern versus western Canada, but the correlation between genotypic effects across these regions was 0.83, In a selection experiment, subdivision of the eastern or western regions did not increase response. Selection in the east produced greater yields in both the east and west. The same genotype ranked first for yield in both regions. There was little specific adaptation to subregions, and two-row barley genotypes were broadly adapted across northern North America. Further subdivision of the regions is unwarranted, and selection in either region is likely to result in response in the other. The lack of local adaptation indicates that breeding programs that test broadly are likely to outperform ones that are narrowly targeted.