Comparative analysis of oil and protein content and seed yield of five Brassicaceae oilseeds on the Canadian prairie

•Oil and protein contents of the oilseed crops are in a linear inverse relationship.•On average, each unit of seed oil increase decreases protein content by 0.69 unit.•Oil content was highest in B. napus, while protein content was highest in S. alba.•The oil and protein contents are influenced by site-specific growth environments.•B. juncea and carinata can be used as feedstock for both oil and protein industry.