GENOTYPE × ENVIRONMENT INTERACTION AND STABILITY ANALYSIS OF SEED YIELD OF OILSEED RAPE GROWN IN MANITOBA

Genotype × environment interactions, cultivar response to environments and cultivar stability for yield of oilseed rape (Brassica napus L.) were studied using five cultivars grown for 3 yr at nine locations in Manitoba. The objectives were: (1) to estimate the components of variance associated with the first- and second-order interactions and to determine their effects on the standard error of a cultivar mean so that optimum test combinations of replications, locations and years for cultivar testing in Manitoba could be determined; (2) to measure cultivar response to varying environments; and (3) to measure cultivar stability. The genotype × year and the genotype × year × location interactions were significant. The genotype × location interaction was not significant, indicating the cultivars tested performed similarly relative to each other across locations over years. Increasing years, locations and replications in that order had the greatest effects on the standard error of a cultivar mean. Calculation of the contribution of each variety to the G × E sums of squares indicated that Westar made the largest contribution and Altex the smallest.Key words: Rape (oilseed), Brassica napus L., stability, cultivar testing