Yield has minimal effect on whole-grain mineral density of modern soft wheat compared to production environment, genotype, and test weight

Abstract

ProblemMillions of people worldwide lack diversified diets and rely on staple foods, like wheat, that are inherently poor in minerals as primary sources of 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 impactful genetic differences (e.g., tall vs. semi-dwarf), but there is much less clarity in studies focused on modern genotypes. ObjectiveThe objective of this research was to better understand factors affecting concentrations of eight minerals in whole-grain soft white wheat, especially yield. MethodsThis was done by collecting a genetically and environmentally diverse grain mineral dataset and analyzing it in multiple ways. ResultsThere 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 was present, but it was insignificant and small relative to other sources of variation. Production environment had the greatest impact on grain minerals, contributing between 50% and 90% of variation in the data, depending on the mineral. Wheat genotype had an impact on density of most minerals and genotype by environment interactions were common. 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 also had a significant impact on concentrations of two minerals (K and Cu). 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. ImplicationsIn 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, the minor negative impact of yield should be considered secondarily to much more significant factors like production environment, wheat genotype, and even test weight.