Location: Hard Winter Wheat Genetics ResearchTitle: Variation for nitrogen use efficiency traits in current and historical Great Plains hard winter wheat Author
|Baenziger, P. Stephen|
Submitted to: Euphytica
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/1/2017
Publication Date: 3/15/2017
Citation: Guttieri, M.J., Frels, K., Regassa, T., Waters, B., Baenziger, P. 2017. Variation for nitrogen use efficiency traits in current and historical Great Plains hard winter wheat. Euphytica. 213:87. doi:10.1007/s10681-017-1869-5. Interpretive Summary: Wheat varieties that efficiently capture and convert available soil nitrogen into grain protein are key to sustainably meeting the rising global demand for grain protein. Therefore variation for nitrogen use efficiency within hard winter wheat adapted to the Great Plains of the United States was measured. Both historically important and contemporary varieties and breeding lines were included in the set of 299 winter wheat lines. Hard winter wheat breeders of the Great Plains have improved NUE: the subset of 183 wheats that were released as cultivars after 1960 demonstrated significant genetic improvements in most measures of nitrogen use efficiency. Differences in plant height and flowering date explained much of the variation in nitrogen use efficiency. Consequently, new wheat germplasm that may have useful characteristics for nitrogen use efficiency will be difficult to identify unless plant height and flowering date are optimal in the target growing region. Measurement of nitrogen use efficiency is expensive because it is labor-intensive. Therefore molecular markers associated with nitrogen use efficiency are important tools for selection of improved wheat varieties. Several molecular markers associated with nitrogen use efficiency were identified. The region of the wheat genome near the most widely used gene for semi-dwarf stature, the "green revolution" gene RhtB1b, was important for nitrogen use efficiency. However, the most favorable gene(s) appear to be widely used in current varieties. A region of the wheat genome on the long arm of chromosome 2D also was important for nitrogen use efficiency. In this case, the most favorable gene(s) were not widely used in current varieties, which indicates that there may be opportunities for improving wheat nitrogen use efficiency by selection using markers in this region of the wheat genome.
Technical Abstract: Wheat genotypes that efficiently capture and convert available soil nitrogen into harvested grain protein are key to sustainably meeting the rising global demand for grain protein. The purposes of this study were to characterize the genetic variation for nitrogen use efficiency (NUE) traits within hard winter wheat adapted to the Great Plains of the United States, to explore relationships among traits that may be used for selection within breeding programs, and to identify quantitative trait loci associated with NUE traits in this germplasm. NUE traits were measured in a panel of 299 hard winter wheat genotypes, representing historically important and contemporary germplasm, from across the growing region. Trials were grown in two years at two levels of nitrogen fertility. Genotype and genotype × year interaction effects were highly significant for NUE traits, while genotype × nitrogen rate interactions were non-significant. Strong genetic correlations of plant height and flowering date with NUE traits were observed. Wheat breeders have improved NUE: the subset of 183 genotypes that were released as cultivars after 1960 demonstrated significant trends with year of release for improved grain N yield, grain yield, nitrogen harvest index, nitrogen uptake efficiency, nitrogen utilization efficiency, and post-anthesis nitrogen uptake. In genome-wide association analyses, plant height and flowering date were important covariates in the mixed models, and plant height and flowering date substantially explained the variation in NUE traits in this germplasm. A limited set of significant marker-trait associations were recovered that may prove useful in breeding.