Detailed phenotypic assessment of genetic variation for nitrogen uptake and utilisation efficiency traits in a diverse panel of Brassica napus L.
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Rapeseed, (Brassica napus L.) is a crop of major economic importance, mainly grown for its oil-rich seeds. These are used for human consumption as well as for industrial purposes, and the seedcake serves as an important protein source in livestock feeding. It is the third most important oil crop in the world, behind soybean and palm oil. However, rapeseed production requires a relative high mineral nitrogen (N) inputs. For this reason an enhanced nitrogen use efficiency (NUE) has become a major aim in rapeseed production in order to ensure a sustainable agricultural production, particularly in association with the reduced release of nitrogen-derived greenhouse gases from soils and nitrate contamination of waterways. The use of genetic variation to breed more efficient varieties is seen a promising option to improve agricultural sustainability, but first requires detection of suitable variants by appropriate phenotyping procedures. To address this issue, this study assessed 30 diverse winter oilseed rape accessions under contrasting nitrogen fertilisation levels for physiological traits at several developmental stages, covering the entire vegetation period from 28 days after sowing until seed harvest and comparing detailed results from multiple experiments.An in vitro hydroponic growth system was used to screen the material at a very early stage with regard to nitrogen acquisition. Besides a variation in shoot N content of more than 60%, and root N content of more than 70%, a higher root-shoot ratio under limiting N was determined. Moreover, cross-correlations of 33 physiological traits associated with N uptake or utilisation efficiency revealed considerable variation for NUE parameters, including positive effects of early flowering and high leaf N concentration on enhanced N utilisation under low N input. Furthermore, seed yield per se was found to be more important than the seed N concentration for simultaneously achieving both high N utilisation and reduced N balance surplus.Additionally, a plant growth system comprising 120 large, 90 cm deep containers was established to allow phenotyping of the root system at an adult developmental stage. Comparison of seed yield from container grown plants to three field locations revealed a good transferability of phenotypic data from the semi-controlled environment to field conditions, encouraging use of this system for further physiological studies of N-mediated genotype responses.Finally, phenotyping of the root system provided new insights into genetic variation for root biomass and degree of fine rooting, as well as the response to divergent nitrogen fertilisation levels. Furthermore, huge variation was seen for nitrogen losses with aborted leaves. Collectively, the results of this study suggest a considerable scope for further NUE improvement in oilseed rape by targeted combination of contributing factors in new, high-yielding varieties.Verknüpfung zu Publikationen oder weiteren Datensätzen
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Andreas Stahl, Wolfgang Friedt, Benjamin Wittkop, Rod Snowdon (2016): Complementary diversity for nitrogen uptake and utilisation efficiency reveals broad potential for increased sustainability of oilseed rape production. Plant and Soil 400: 245-262, doi: 10.1007/s11104-015-2726-8.