Yield has minimal effect on whole-grain mineral density of modern wheat compared to production environment

Authors: Adams, Curtis; GRAEBNER, RYAN - Oregon State University; MARSHALL, JULIET - University Of Idaho; NEELY, CLARK - Washington State University; LONG, DANIEL - Collaborator; Reardon, Catherine - Kate; Rogers, Christopher

Submitted to: Field Crops Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/1/2024
Publication Date: 5/9/2024
Citation: Adams, C.B., Graebner, R.C., Marshall, J., Neely, C., Long, D.S., Reardon, C.L., Rogers, C.W. 2024. Yield has minimal effect on whole-grain mineral density of modern wheat compared to production environment. Field Crops Research. 312. Article 109403. https://doi.org/10.1016/j.fcr.2024.109403.
DOI: https://doi.org/10.1016/j.fcr.2024.109403

Interpretive Summary: People worldwide lack diversified diets and rely on wheat and other staple foods as primary sources of mineral nutrients, such as Zn, K, Fe, and others. Cereal grains are inherently poor in minerals, however. Efforts have been made to enhance the amount of minerals in wheat through plant breeding and crop management, though there is concern that mineral concentration will decrease if yield increases. But there is not clear understanding on how yield might affect minerals in modern wheat. In this research project, wheat samples were collected from many wheat varieties included in studies conducted across the Pacific Northwest states of Oregon, Idaho, and Washington and analyzed for minerals. There was no effect of yield on density of any tested mineral in grain when factors such as production environment and test weight were controlled. Production environment had the greatest impact on grain mineral density, followed by wheat genotype and grain test weight. The results suggest that breeding for increases in grain minerals will be most successful for Zn, P, and Mg. In summary, this analysis provides evidence that the impact of yield on grain mineral density among modern wheat germplasm is small and insignificant. In the quest to improve the mineral nutrient value of wheat through plant breeding, crop management, and other approaches, yield should be considered secondarily to much more significant factors like production environment, wheat genotype, and even test weight.

Technical Abstract: Millions of people worldwide lack diversified diets and rely on staple foods, like wheat, that are inherently poor in minerals as primary sources of mineral nutrition. Efforts have been made to enhance grain mineral density in wheat through plant breeding and crop management, though there is concern that mineral "dilution" will occur if higher yield is also sought. Much of that concern comes from studies comparing historic and modern wheat genotypes with large genetic differences (e.g. tall vs. semi-dwarf), but there is much less clarity in studies evaluating only modern genotypes. Therefore, the objective of this research was to collect a genetically and environmentally diverse dataset and analyze it in multiple ways to better understand factors affecting concentrations of eight minerals in whole-grain wheat. There was no significant effect of yield on density of any tested mineral in grain when factors such as production environment and test weight were controlled, though regression coefficients for yield were generally negative. Thus, the negative effect of yield on grain mineral density was present, but insignificant and small relative to other sources of variation. Production environment had the greatest impact on grain mineral density, contributing between 50% and 90% of variation in the data, depending on the mineral. Wheat genotype had an impact on density of most minerals in grain and genotype by environment interactions were common. The results suggest that achieving genetic gain in elevating grain minerals through plant breeding may be most successful for Zn, P, and Mg, because genotypic variation and heritability were relatively high for these minerals. Further analysis of Zn showed that breeding selection for simultaneously high-Zn, high-yield wheat varieties is possible, because individual wheat varieties tended to have consistent grain Zn relative to the mean, regardless of yield level or production environment. Grain test weight (i.e. specific weight) also had a significant impact on concentrations of several minerals. Factors that impact plant health and metabolism, and ultimately grain test weight, are likely to also affect plant mineral uptake and translocation, possibly causing this association. In summary, this analysis provides evidence that the impact of yield on grain mineral density among modern wheat germplasm is small and insignificant. In the quest to improve the mineral nutrient value of wheat through plant breeding, crop management, and other approaches, yield should be considered secondarily to much more significant factors like production environment, wheat genotype, and even test weight.