In the coming decades, climate change and resources constraints will make profitable and economically reliable agriculture more and more challenging. To evaluate the potential of exotic alleles to maintain performance under low nitrogen input, we investigated a set of 41 introgression lines (S42ILs) originating from the hybridization of the German spring barley 'Scarlett' and the Israeli wild barley 'ISR42-8'. These lines were assessed in field trials for yield, yield components, grain protein content and chlorophyll content during growing seasons 2015 and 2016 in two different test sites in Germany under low and high nitrogen supply levels, N 0 and N 1 . Our analyses revealed 17 regions for putative quantitative trait loci (QTL), linked to one or multiple traits, across all chromosomes. In particular, lines S42IL_119 and S42IL_121 exhibited an enhanced thousand grain weight of 7% and 9% under N 1 and N 0 , respectively. In addition, six QTL were found for grain number per ear leading to a decline of grain number of up to 20%. Furthermore, three new QTL for chlorophyll content could be identified on chromosomes 1H and 2H. The present study revealed QTL effects of wild barley introgressions in a spring barley elite background, especially under low nitrogen. The selection for nitrogen efficient lines with beneficial exotic alleles represents the first step towards the development of spring barley cultivars genetically adapted to nitrogen limitations.
A rotational field experiment was established in the year 2002 at the experimental farm Etzdorf in the Hercynian dry region of central Germany. Since 2005 field measured datasets were used to determine the effect of different preceding crop combinations and different nitrogen (N) fertilisation treatments on the seed yield, oil content, oil yield and N-use efficiency of oilseed rape (Brassica napus L.). The preceding crop combinations compared were winter wheat (Triticum aestivum L.)-winter wheat (WW), WW-oilseed rape (OSR), OSR-OSR and an OSR monoculture. In addition to the preceding crop combination, N fertiliser treatments with either 120 kg N ha–1 or 180 kg N ha–1 were established in the year 2013.
Overall the results demonstrated that seed yield, oil yield and N-use efficiency all declined with an increased cropping intensity for the period 2005–2012. Higher N rates in the 2013–2014 seasons increased seed yield and oil yield when OSR followed WW-WW pre-crops. OSR monoculture had lowest yield independent of applied N. Seed yield declined from 4.61 t ha–1 (OSR following WW-WW) to 4.28 t ha–1 in the OSR monoculture with 120 kg N ha–1, and from 4.81 t ha–1 (following WW-WW) to 4.42 t ha–1 in the OSR monoculture with 180 kg N ha–1. Higher N rates generally reduced N-use efficiency, with highest N-efficiency for WW-WW-OSR (38.4 kg kg–1), and lowest for continuous OSR receiving 180 kg N ha–1 (24.5 kg kg–1).
These results emphasise the importance of crop rotation to maintain seed yield and oil yield of oilseed rape, and to maximise the response to applied N. A reduced N rate increased N-use efficiency and reduced the risk of high N surpluses without a significant/equivalent decrease of the seed yield when the rotation was optimised.
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