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

Abstract

Studies have generally shown that grain mineral density is lower in modern wheat (Triticum aestivum L.) compared to historic germplasm. The conclusion of a limited study from the US Pacific Northwest (PNW) was that grain mineral density of soft white wheat (SWW) had declined over time to meet already-low mineral density of hard red wheat (HRW), though little else is known about this. Therefore, the primary objective of this study was to better understand grain mineral density (P, K, Mg, Ca, Mn, Fe, Zn, and Cu) of modern PNW wheats, with subobjectives to compare SWW and HRW wheat classes to each other and worldwide benchmarks, quantify effects of agronomic factors on grain minerals, and evaluate minerals in refined flour. Results indicated whole-grain mineral density of PNW wheat was comparable to worldwide benchmark concentrations, with P and K most likely low, with no evidence of SWW and HRW class differences. Agronomically, there was significant variation in grain minerals among production sites and wheat varieties that could be utilized to generate mineral-enriched grain to feed malnourished populations. In the process of refining flour from whole grain, the minerals most reduced were P, Mg, Mn, Fe, Zn, and Cu (60%–90%). Refined flour mineral concentrations were largely unassociated with flour yield or quality parameters, suggesting that efforts to enhance mineral density 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.