Trade-off between oil and protein in rapeseed at high latitudes: Means to consolidate protein crop status?

Crop-derived feed protein production is alarmingly low in Europe. Finland represents the northernmost growing region in the world and consequently lacks wide-ranging alternatives to improve crop-based protein production. Spring rapeseed, both turnip rape (Brassica rapa L.) and oilseed rape (Brassica napus L.), are adapted to such northern conditions. This study examines the potential for genotype and environment induced trade-off between oil and protein in rapeseed in order to enhance further the status of rapeseed as a protein crop for northern areas. Datasets on advanced breeding progenies (including cultivars) were provided by Boreal Plant Breeding Ltd., while environment-induced variability in combinations of protein and oil content was studied by using long-term, multi-location datasets of MTT Official Variety Trials. Oilseed rape has more potential as a protein producer than turnip rape, with some 100 kg/ha difference in protein yields. Selecting lines superior in seed protein content at the expense of oil was not a potential means to consolidate protein production capacity per hectare: seed and protein yields were higher the better the capacity of the line to store oil. This can only mean that obviously the lower energy demand for oil synthesis was not alternatively used to boost protein production, but actually vice versa. In the case of environment-induced variation, the highest protein yields were produced in experiments where relatively high protein content was associated with modest oil content, but such conditions were characterised as inefficient in general production capacity and thereby, excessive in applied nitrogen fertiliser. Hence, we were not able to identify promising opportunities for prompt and energy-efficient trade-off between protein and oil in rapeseed.

Research highlights▶ Oil seed rape produces higher protein yield than turnip rape in northern conditions. ▶ Lines superior in seed protein did not produce superior protein yields per hectare. ▶ High yielding lines with high oil content produced the highest protein yields.