Utilize the Genetic Potential: Breeding Progress Towards Nitrogen Use Efficiency in Brassica napus L

Fertilization with nitrogen is one of the most agronomic important factors contributing to maintenance of the high seed yields needed to match food and non-food demand for a strongly increasing world population. However, significant quantities of fertilized N escape into groundwater, rivers and ocean or in the form of volatile losses into the atmosphere. Although nitrogen fertilization will remain essential to achieve high yield levels in future, production of agricultural commodities must simultaneously reduce negative impacts on ecosystems.

The recent allopolyploid oilseed rape (Brassica napus L.), the third-most important oil crop worldwide after perennial oil palm and soybean, has multiple uses in food and non-food products. Furthermore, oilseed rape cultivation is part of a sustainable crop rotation. Compared to other crops, however, oilseed rape releases a high nitrogen balance surplus requiring improvements in nitrogen use efficiency (NUE).

We assessed diversity for NUE at six locations across Germany. 30 elite inbred and hybrid varieties, covering 25 years of breeding progress, were grown under two distinct nitrogen fertilization levels (120 and 220 kg N/ha). Alongside seed yield and quality parameters we also conducted a biomass harvest at flowering. This enabled us to differentiate between nitrogen uptake and utilization efficiency. For both parameters we observed significant differences between hybrid and inbred varieties. Analysis of inter-trait relationships among more than 20 morpho-physiological traits enabled us to elucidate the key factors contributing to superior NUE and a positive agro-ecological balance in modern hybrids.