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Title: Genotypic differences for nitrogen use efficiency and grain protein deviation in hard winter wheat

Author
item LATSHAW, SUSAN - COLORADO STATE UNIVERSITY
item VIGIL, MERLE
item HALEY, SCOTT - COLORADO STATE UNIVERSITY

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/27/2016
Publication Date: 11/3/2016
Citation: Latshaw, S., Vigil, M.F., Haley, S. 2016. Genotypic differences for nitrogen use efficiency and grain protein deviation in hard winter wheat. Agronomy Journal. 108:6/2201-2213. doi:10.2134/agronj2016.02.0070.
DOI: https://doi.org/10.2134/agronj2016.02.0070

Interpretive Summary: To bake a quality loaf of bread the wheat flour must have protein contents above 12%. Because proteins are nitrogen (N) based compounds the N fertility of the soil where the wheat is grown becomes important. However, N fertility is not the only factor affecting wheat protein content. Both the management of the wheat crop and the cultivar grown will also impact protein content. Differences in cultivars, known as genetic variability, along with yield potential and N availability will also affect grain protein content. In this study we evaluated 20 diverse winter wheat cultivars under 5 different N availability regimes in a large field experiment over a two year period. The difference in N availability was imposed by applying fertilizer N rates that increased incrementally. N rates used were: 0, 28, 56, 84, 112, and 140 kg N ha-1 and all were applied shortly after planting. In all cases, the lowest protein contents were measured in the 0 N rate plots. Cultivar differences were harder to defined but there were consistent differences in that the cultivar Brawl-CL had greater grain protein content at a given yield level than the average for the twenty cultivars tested. In general, for all cultivars as N rate increased protein content increased. In some years for some cultivars the yield also increased slightly with the first increment of N applied.

Technical Abstract: Nitrogen use efficiency and grain protein deviation were determined among twenty hard winter wheat (Triticum aestivum L.) genotypes under five N application rates in one season and for two recently released varieties (Snowmass PI658597 and Byrd PI664257) in a second season. We characterized the relative contributions of component traits to variance for N use efficiency. Among these 20 genotypes, variance for N use efficiency among genotypes was contributed by differing proportions of N uptake efficiency (57-89 kg kg-1) and N utilization efficiency (11-43 kg kg-1). Across all genotypes, N utilization efficiency contributed the most to variance for N use efficiency under moderate to high N supply while N uptake efficiency contributed more under N limiting conditions. Increased N use efficiency promotes high grain yields, but may result in decreased grain N concentration through the commonly observed negative correlation of these traits. Analysis of residuals from regression of grain protein concentration on grain yield, or ‘grain protein deviation’, distinguished one genotype that had higher grain protein concentration than predicted for the level of grain yield. Grain protein deviation in the cultivar Brawl CL Plus predicted 6.7 g kg-1 more protein at a given yield level than the average for the twenty genotypes.