Abstract
Oilseed rape is one of the most important dicotyledonous field crops in the world, where it plays a key role in productive cereal crop rotations. However, its production requires high nitrogen fertilization and its nitrogen footprint exceeds that of most other globally important crops. Hence, increased nitrogen use efficiency (NUE) in this crop is of high priority for sustainable agriculture. We report a comprehensive study of macrophysiological characteristics associated with breeding progress, conducted under contrasting nitrogen fertilization levels in a large panel of elite oilseed rape varieties representing breeding progress over the past 20 years. The results indicate that increased plant biomass at flowering, along with increases in primary yield components, have increased NUE in modern varieties. Nitrogen uptake efficiency has improved through breeding, particularly at high nitrogen. Despite low heritability, the number of seeds per silique is associated positively with increased yield in modern varieties. Seed weight remains unaffected by breeding progress; however, recent selection for high seed oil content and for high seed yields appears to have promoted a negative correlation (r= -0.39 at high and r= -0.49 at low nitrogen) between seed weight and seed oil concentration. Overall, our results reveal valuable breeding targets to improve NUE in oilseed rape.
Highlights
Agricultural production must increase global crop yields dramatically in order to match growing demand from a predicted world population of ~9 billion people by 2050 (Tilman et al, 2002)
The leaf C concentration was not significantly different between low N and high N (42.73% versus 42.83%), significant variation caused by the genotype for leaf concentration of both N and C was determined within both N fertilization levels.Variation for N in leaves ranged from 3.40% to 4.01% at low N (P-value
These results suggest that thousand seed weight (TSW) is not significantly influenced by selection, allowing two possible conclusions: (i) variation in TSW does not contribute to yield improvement and is not influenced by breeding programs focusing solely on yield selection per se; or (ii) enhanced TSW might be beneficial for seed yield increase but the effects are masked by other factors influencing seed yield, preventing breeders from actively considering TSW in selection decisions
Summary
Agricultural production must increase global crop yields dramatically in order to match growing demand from a predicted world population of ~9 billion people by 2050 (Tilman et al, 2002). Since arable land is limited, yield improvements per unit area are of utmost importance. In most regions, this is associated with fertilization with nitrogen (N), the quantitatively most important nutrient required for crop growth. Solving the conflict between the need for yield increases, without compromising crop product quality or ecosystem health through excessive N losses, necessitates tremendous enhancement of nitrogen use efficiency (NUE) in major crops
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