Identifying canola (Brassica napus L.) accessions with superior photosynthetic traits and unique resource partitioning strategies

Canola (Brassica napus L.) yields in Canada are not increasing sufficiently to meet future global demands. Improving photosynthetic efficiency and optimizing photoassimilate allocation represent a promising strategy to enhance yield potential. This study evaluated the photosynthetic and agronomic traits of 168 diverse canola accessions belonging to six pedigree groups: spring canola × spring canola (SP × SP), spring canola × winter canola (WI × SP), spring canola × rutabaga (B. napus var. napobrassica) (SP × RU), (winter canola × spring canola) × rutabaga ([WI × SP] × RU), spring canola × B. oleracea (SP × BO), spring canola × B. rapa (SP × BR), and accessions collected from the Plant Gene Resources of Canada, Saskatoon collection. Field experiments conducted over three growing seasons in Central Alberta, Canada, identified moderate to high heritability for four chlorophyll fluorescence parameters and five agronomic traits. Distinct source-sink allocation strategies emerged among pedigree groups. The SP × SP group optimized resource allocation for maximal seed yield, while winter canola-derived groups prioritized seed size (1000-seed weight) while maintaining competitive yields, likely through extended grain-filling periods. Unique physiological linkages were observed in progenitor-derived groups: SP × BR accessions exhibited coordinated regulation of non-photochemical quenching photoprotection, biomass production, and yield, whereas SP × BO demonstrated an association between root biomass and reduced minimal fluorescence (F_o′), suggesting improved PSII efficiency. These findings highlight the value of physiological trait-based selection in canola breeding. The identified germplasm and trait relationships provide a foundation for developing improved spring canola cultivars through targeted integration of favorable photosynthetic and allocation characteristics.