The impact of nutrition on the gluten composition and processing quality of wheat (PhD)

ABSTRACT   

Understanding nutrition is important for improving the quality and yield of crop plants but is also a vital aspect of increasing the sustainability of crop production through better resource use efficiency. This study used the Broadbalk experiment, which is the longest running agricultural experiment in the world, together with modern analytical techniques, to improve the understanding of wheat nutrition. Transcriptomics analysis, using Affymetrix Wheat Genechips®, showed that there are significant differences in gene expression profiles between wheat grain from plants treated with organic and inorganic fertilisers. Metabolomic fingerprinting using NMR spectroscopy and GC-MS showed that wheat crops grown with higher availability of nitrogen had increased levels of free amino acids in the developing endosperm and in the white flour. Analysis of the grain protein composition using SE-HPLC and SDS-PAGE revealed characteristic changes in protein composition associated with the availability of nitrogen, including an increase in the ratio of gliadin to glutenin subunits. These effects were related to changes in the functional properties of dough made from the white flour. Effects that were seen in samples from the Broadbalk experiment could be related to differences in commercially produced grain from organic and conventional farms. This demonstrates that nutritional treatments associated with these two cultivation systems are important in contributing to differences in end product quality. In addition, the effects of foliar urea treatment after anthesis were similar to the effects of increased nitrogen application rate to the soil much earlier in crop development.