Yi-Xiang Wang, Baijuan Du
Background: Maize shoot height is an important component of early vigor and plant architecture; however, its genetic basis during seedling development and its relationship with modern breeding remain insufficiently understood. This study aimed to investigate the genetic architecture of maize seedling shoot height across different breeding eras. Methods: Shoot height at 21 days after sowing was evaluated in 363 maize inbred lines representing three breeding eras in China. Genome-wide association analysis was performed to identify loci and candidate genes associated with shoot height variation, and selective sweep analysis was used to detect breeding-era differentiated genomic regions. Results: Modern breeding lines from the 2000–2010s exhibited significantly greater shoot height than lines from earlier breeding periods. Pearson’s correlation analysis revealed that 3-week shoot height showed highly significant positive correlations with plant height and ear height. Selective sweep analysis identified multiple differentiated genomic regions harboring previously reported height- and architecture-related genes, including ZmBR2, ZmLIL1, ZmNA1, ZmTE1, ZmSPL12, ZmBV1, ZmDIL1, ZmKN1 and ZmACS7. The GWAS identified 43 SNPs exceeding the GEC-derived suggestive threshold for shoot height, with the strongest and most continuous association signal located on chromosome 8. GWAS, together with LD analysis, haplotype analysis, and expression profiling, prioritized ZmGDCL (Zm00001d009163) as a promising candidate gene because of its strong association signal, local linkage disequilibrium support, broad expression profile, and significant haplotype effect on shoot height. Conclusions: Our results indicate that maize breeding has reshaped the genetic architecture of seedling shoot growth. ZmGDCL represents a promising candidate gene for future functional studies, while breeding-era differentiated regions provide useful genomic context for understanding maize architecture improvement.