Dynamics and genetic regulation of macronutrient concentrations during grain development in maize

Nitrogen, phosphorus, and potassium are essential macronutrients crucial not only for maize growth and development, but also for crop yield and quality. The genetic basis of macronutrient dynamics and accumulation during grain filling in maize remains largely unknown. In this study, we evaluated grain N, P, and K concentrations in 206 recombinant inbred lines generated from a cross of DH1M and T877 at six time points after pollination. We then calculated conditional phenotypic values at different time intervals to explore dynamic characteristics of N, P, and K concentrations. Abundant phenotypic variation was observed in the concentration and net changes of these nutrients. Unconditional quantitative trait locus (QTL) mapping revealed 41 non-redundant QTLs, including 17, 16, and 14 for N, P, and K concentrations, respectively. Conditional QTL mapping uncovered 39 non-redundant QTLs related to net changes in N, P, and K concentrations. By combining QTL, gene expression, co-expression analysis, and comparative genomic data, we identified 44, 36, and 44 candidate genes for N, P, and K concentration, respectively, including GRMZM2G371058 encoding a Dof-type zinc finger DNA-binding family protein, associated with N concentration, and GRMZM2G113967 encoding a CBL-interacting protein kinase, related to K concentration. Our results should deepen understanding of genetic factors controlling N, P, and K accumulation during maize grain development and provide valuable genes for genetic improvement of nutrient concentrations in maize.