Genetic basis of pedicellate spikelet masculinization in maize revealed by an advanced maize-teosinte population

The sex differentiation of maize florets is critical for yield, yet its developmental regulatory mechanism remains unelucidated. Our study establishes valuable genetic loci for cloning the causative gene(s) underlying pedicellate spikelet masculinization. As a typical monoecious species, maize produces a tassel at the apex and an ear in the leaf axils, each consisting of paired sessile and pedicellate spikelets of the same sex. However, the developmental mechanisms governing sexual differentiation between the sessile and pedicellate spikelets remain poorly understood. In this study, we focused on a unique phenotype-pedicellate spikelet masculinization (PSM) in the ear-which was lost during domestication but reappeared in a maize introgression line containing chromosome segments from teosinte. Firstly, a novel and stable major QTL, qPSM3-1, located on chromosome 3, was identified in three advanced mapping populations: BC₄F₂, BC₅F₂, and BC₅RIL, explaining 29.95%, 24.72%, and 46.79% of the phenotypic variation, respectively. To further explore additional loci influencing the PSM phenotype, a residual heterozygous population was constructed based on the fixed major QTL qPSM3-1 to detect minor-effect QTLs. By integrating QTL-seq with traditional linkage mapping, two minor-effect QTLs, qPSM4-1 and qPSM8-1, were identified on chromosomes 4 and 8, accounting for 8.52% and 6.73% of the phenotypic variation, respectively. Collectively, these findings provide crucial genetic resources for cloning the gene(s) responsible for pedicellate spikelet masculinization and offer new insights into the complexity of plant sex determination mechanisms.