Canola yield and its association with phenological, architectural and physiological traits across the rainfall zones in south-western Australia

•Multiple-environment trials were used to understand yield and associated traits.•Genotype × environment interaction reveals two environment and four genotype clusters.•Flowering time, biomass and harvest index were the main factors determining yield.•Both specific and broad adaption were identified. Understanding genotype and environment interaction (G × E) and the association between yield and phenological, architectural and physiological traits plays a crucial role in successful canola breeding and agronomic management. We investigated yield performance of 20 open-pollinated and hybrid canola across multiple environments over five years and its association with these traits. Heterogenic genetic variance and genetic correlation among the environments demonstrated significant G × E interactions in yield, biomass, but not in harvest index (HI). Flowering time, biomass at maturity and HI are the three most important traits underlying the G × E interaction. Principal component analysis (PCA) based on the yield across the environments identified two mega-environments (the low/medium rainfall zone (LMRZ) and the high rainfall zone (HRZ)) and four genotype clusters (early-flowering, late-flowering, average performing, and broadly adapted varieties). Early flowering genotypes were better adapted to the LMRZ mega-environment and late-flowering ones to the HRZ mega-environment. Despite the G × E interaction, a group of hybrid varieties were identified as broadly adapted, producing either the highest or similar yield to specifically adapted varieties. The genotype by trait PCA revealed that yield was positively associated with biomass and HI but negatively with flowering time in the LMRZ mega-environment. In contrast, yield was positively associated with increased biomass, late-flowering but negatively with HI in the HRZ mega-environment. In both mega-environments, HI was negatively correlated with delay in flowering and increased plant height and biomass. Reducing plant height in late flowering hybrid varieties offers a solution to the trade-off between biomass and HI. It can have the potential to increase yield by increasing HI while maintaining biomass in the HRZ mega-environment.