As grain mineral densities have declined over time, have densities converged across wheat classes? Insights from the U.S. Pacific Northwest and worldwide benchmarks

Authors: Adams, Curtis; KONGRAKSAWECH, TEEPAKORN - Oregon State University; ROSS, ANDREW - Oregon State University; LONG, DANIEL - Collaborator; NEELY, CLARK - Washington State University; GRAEBNER, RYAN - Oregon State University; MARSHALL, JULIET - University Of Idaho; Reardon, Catherine - Kate; LIANG, XI - University Of Idaho

Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/14/2024
Publication Date: 12/12/2024
Citation: Adams, C.B., Kongraksawech, T., Ross, A., Long, D.S., Neely, C., Graebner, R.C., Marshall, J., Reardon, C.L., Liang, X. 2024. As grain mineral densities have declined over time, have densities converged across wheat classes? Insights from the U.S. Pacific Northwest and worldwide benchmarks. Crop Science. 65(1).e21409. https://doi.org/10.1002/csc2.21409.
DOI: https://doi.org/10.1002/csc2.21409

Interpretive Summary: Little is known about the mineral nutrient density (e.g., (P, K, Mg, Ca, Mn, Fe, Zn, and Cu) of soft white wheat produced in the U.S. Pacific Northwest (PNW) and elsewhere, including how the nutritional density compares to other classes of wheat and to wheat globally. The mineral density of wheat is important because it is consumed by human populations that rely on it as a primary source of mineral nutrition in their diets. The several objectives of this study included comparing PNW wheat mineral density to worldwide benchmark concentrations, evaluating the effects of agronomic factors on grain mineral density, comparing minerals in soft white and hard red wheats, and evaluating minerals in refined flour. When comparing PNW grain minerals to worldwide benchmarks, PNW wheats were comparable overall, though grain P and K were most often low, though Zn was also low at several sites. Among agronomic factors affecting whole-grain mineral densities, N fertilizer had little impact, wheat variety was intermediate, and production site had the greatest effect overall. In comparing grain mineral density of soft white and hard red wheats, there was no evidence of differences between wheat classes. In the flour refining process, the minerals most negatively impacted were P, Mg, Mn, Fe, Zn, and Cu, with reductions relative to whole-grain ranging from roughly 60% to 90%. Variation in refined flour mineral concentrations had few associations with flour yield or quality parameters. Overall, these results illustrate that the mineral nutrient density of soft white wheat is comparable to hard red and to wheat produced globally. Importantly, consumption of whole-grain wheat products should be promoted and expanded to preserve and utilize the inherent nutrition of wheat in relieving human mineral deficiencies.

Technical Abstract: Studies have generally shown that grain mineral density is lower in modern wheat compared to historic germplasm. The conclusion of a study from the U.S. Pacific Northwest (PNW) was that grain mineral density of soft white wheat (SWW) had declined over time to meet historically low mineral density of hard red wheat (HRW), though little else is known about this. Therefore, the objective of this study was to better understand grain mineral density (P, K, Mg, Ca, Mn, Fe, Zn, and Cu) of modern PNW wheats, including comparing two wheat classes (SWW and HRW) to each other and worldwide benchmarks, quantifying effects of agronomic factors, and evaluating refined flour. Whole-grain mineral density of PNW wheat was comparable to worldwide benchmark concentrations, with P and K most likely to be low. There was no evidence of SWW and HRW class differences. There was significant variation in grain minerals among production sites and wheat varieties that could be utilized to generate mineral-enriched grain for malnourished populations. In the process of refining flour, the minerals most reduced were P, Mg, Mn, Fe, Zn, and Cu (60% to 90% reductions from whole grain). Refined flour mineral concentrations were largely unassociated with flour yield or quality parameters, suggesting that enhancing mineral nutrient value will not affect other flour traits. Overall, these results illustrate that the mineral density of modern SWW and HRW produced in the PNW are comparable to each other and to wheat globally. Considering reported historical changes, these results suggest a modern, worldwide convergence in mineral density across wheat classes.