The influence of nitrogen fertilisers on the expression of functional proteins in wheat
About this project
Wheat of the breadmaking variety Hereward was grown at a single site in Suffolk and a number (ten) of fertiliser regimes ranging from 40 to 280 kgN/ha (including a uniform basal level of 40 kgN/ha) were applied in a randomised block system involving four replicates of each treatment. The treatments included both soil-applied ammonium nitrate and foliar- applied urea.
Immature caryopses (ten spikes per plot) were harvested at weekly intervals from ten days after anthesis and transported frozen to Chorleywood. After freeze-drying, caryopses weight and protein contents were measured. A total of five immature sample sets were handled.
The expression of functional protein (glutenin and gliadin) was monitored using gel eletrophoresis. Results showed that there were no qualitative differences in the proteins expressed in the mature grain, but there was evidence that both high levels of ammonium nitrate and the use of foliar urea resulted in accelerated formation of gliadins.
Of particular note was the finding that the amount of technologically significant high- molecular weight glutenin subunits (HMW-G) found in samples 31 days after anthesis correlated (r=0.84) with the amount found in mature harvested grain. Subject to confirmation with other varieties, HMW-G could be used to monitor crop development allowing targeted application of foliar urea to improve the breadmaking potential of the crop.
The harvested grain was test baked by the Chorleywood Bread Process. Baking performance was highly correlated with protein content (r=0.93), gel-protein content (r=0.94) and SDS sedimentation volume (r=0.94).
The trial showed that foliar urea alone (80 kgN/ha) did not increase grain yield, but the baking performance was better than that achieved with an equivalent amount of ammonium nitrate. This trial showed that good baking performance could be achieved at relatively low levels of nitrogen fertiliser. If confirmed in tests with other varieties, this finding could lead to significant economic and environmental benefits.
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