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Characterization of nitrogen use efficiency in a winter wheat collection

Winter wheat is one of the main cereals that has the greatest importance in human nutrition. It is well known that yield and quality of winter wheat could be dramatically increased through the application of N fertilizers. However, it has been also proved that only a low rate of the applied fertilizers can be utilized by the crops. Therefore, the identification of varieties with better nitrogen (N) uptake and N utilization efficiency is a very important topic. Better understanding of the N utilization capacity of the modern winter wheat varieties could lead to an appropriate fertilizer management, and the better use of N-fertilizers could help to decrease the environmental pollution and economic loss.
Ninety-six winter wheat varieties were investigated under field condition in 2012/2013 growing season. Two different treatments, a control (0 kg/ha) and 120 kg/ha N fertilization level were applied in three replications. Beside the measurement of N content in the grain and straw samples, the effect of N treatment was also characterized by the measurements of agronomically important characters. The main characteristic parameters for the nitrogen usage, the N-use efficiency (NUE) and its two components, namely nitrogen uptake efficiency (NUpE) and nitrogen utilization efficiency (NUtE) were also measured and calculated.
NUE: Kilogram grain dry mass at harvest per kilogram available N (from soil plus fertilizer).
NUE is a product of two definable and independent major sub-traits:
NUpE shows the ability of the crop to capture available N from the soil: Kilogram above-ground N at harvest per kilogram available N (from soil plus fertilizer).
NUtE reflects the ability of the crop to use N to produce grain yield:
Kilogram grain dry mass per kilogram above-ground N at harvest.
The NUpE had a powerful effect on the yield of our winter wheat collection in 2013, while the effect of the NUtE on yield was much less. The vegetation period was very dry (130 mm precipitation), and warm in 2013. On the other hand the availability of the nutrients was low, so the plants suffered from nutrient deficiency. Under this unfavourable circumstance the NUpE parameter was dominant.
The increased NUtE had a negative effect on grain N concentration. We also observed a negative correlation between yield and grain N concentration and a positive relationship between yield and NUtE. According to our data this population (mostly the high-yielding varieties) requires increased nutrient supply to maintain good yield quality (protein content).
The performance of the varieties were scored based on the four most important agronomical traits recorded: yield, harvest index, grain N% and NUE. The quartile performance of the varieties for each of the trait is indicated. It was concluded that different varieties performed better when N was supplied, but it was shown also that several varieties were able to adapt to both conditions.
There was diversity of the nitrogen use potential in the winter wheat population. Because of this polymorphism, the population will be suitable for the forthcoming association mapping planned on the three year screening and DNA-based genotyping data.