Epsilon Open Archive

Abstract

Efficient use of nitrogen (N) is essential to decrease negative impacts of agriculture on the environment. This thesis evaluated the nitrogen use efficiency (NUE) of various wheat varieties, identified traits associated with high NUE and investigated the gene NAM-B1 in relation to some of these traits. To achieve this, a NUE concept was first developed.

Six varieties each of winter and spring wheat (Triticum aestivum ssp. aestivum) at two levels of N fertilisation were studied in a one-year field experiment. A greenhouse experiment was performed with the same six spring wheat varieties at two levels of N fertilisation and three levels of drought. Forty-two varieties of spring wheat were grown in a climate chamber experiment. Furthermore, 527 wheat accessions were genotyped for their allele type of NAM-B1, a gene known to affect grain N concentration and senescence of wheat.

The NUE concept developed here proved relevant in different experimental set-ups, as shown by the varieties ranking similarly in overall NUE and uptake efficiency in the greenhouse and the field. Associations between functional traits and NUE were more evident at low than at high N, suggesting that functional traits might be particularly useful for identifying efficient varieties in limiting N conditions. Grain N content was associated with chlorophyll in the top leaf around anthesis (measured by a SPAD chlorophyll meter) both in the climate chamber and in winter wheat in the field. This suggests that a high SPAD value in a variety can be used as an indicator of high N yield.

Genotyping revealed that the functional allele of NAM-B1 has been preserved in many varieties from Denmark, Finland, Norway and Sweden, but not in varieties from other parts of the world. Swedish varieties with this functional allele did not have higher grain N concentrations, but had accelerated senescence and more ears. Effects of the allele in different environments, e.g. varying temperature and fertilisation, should be further investigated to determine when this allele has positive effects on grain N concentration and yield.