Diversity of Maize Kernels from a Breeding Program for Protein Quality III: Ionome Profiling

Abstract

Densities of single and multiple macro- and micronutrients were estimated in the mature kernels of 1348 accessions in 13 maize genotypes. The germplasm belonged to stiff stalk (SS) and non-stiff stalk (NS) heterotic groups (HGs) with one (S1) to four (S4) years of inbreeding (IB), or open pollination (OP), and with opaque or translucent endosperm (OE and TE, respectively). Indices were calculated for macronutrients (M-Index), micronutrients (m-Index) and an index based on Fe and Zn densities (FeZn-Index). The objectives were to (1) build predictive models and quantify multivariate relationships between single and multiple nutrients with physical and biochemical constituents of the maize kernel; (2) quantify the effects of IB stages and endosperm textures, in relation to carbon and nitrogen allocation, on nutrients and their indices; and (3) develop and test the utility of hierarchical multi-way classification of nutrients with kernel color space coordinates. Differences among genotypes and among IB stages accounted for the largest amount of variation in most nutrients and in all indices, while genotypic response to IB within HGs explained 52.4, 55.9, and 76.0% of variation in the M-Index, m-Index, and FeZn-Index, respectively. Differences in C and N allocation among HGs explained more variation in all indices than respective differences in allocation among endosperm (E) textures, while variation decreased with sequential inbreeding compared to OP germplasm. Specific color space coordinates indicated either large macronutrient densities and M-Index, or large micronutrient densities, m-Index, and FeZn-Index. These results demonstrated the importance of genotypes and the C:N ratio in nutrient allocation, as well as bivariate and multiple interrelationships.

Keywords

• essential micronutrients
• genetic resource
• heterotic groups
• ionome
• opaque endosperm