QTL mapping of maize ear traits and functional analysis of associated genes

Maize yield per unit area is determined by the number of plants per unit area and the yield per plant. Yield per plant is largely dependent on the yield per ear, which is determined by kernel traits. In this research, a high-density genetic map was constructed from a recombinant inbred line (RIL) population comprising 209 lines. QTL mapping was performed for ten ear-related traits: ear length, rows per ear, ear circumference, cob circumference, ear diameter, cob diameter, kernel length, kernel width, kernel thickness, and hundred-kernel weight. A total of 22 QTLs were identified. The QTL locus qKW-1-1, associated with kernel width (KW), was co-localized across two growing seasons and selected as the target locus. Combined with SNP-based screening, 11 target genes with moderate to high effects were identified. Functional validation focused on ZmSMR9 (Zm00001d031546), a gene associated with cell development. Results showed that ZmSMR9 suppressed vegetative growth and promoted reproductive growth in Arabidopsis. It reduced amino acid and starch accumulation, which increased individual seed volume without affecting total yield. In summary, ZmSMR9 may induce premature maturation in Arabidopsis by inhibiting growth, ultimately increasing seed volume through reduced seed set.