The tassel competes with the ear for nutrients and shields the upper leaves, thereby reducing the yield of grain. The tassel branch number (TBN) is a pivotal determinant of tassel size, wherein the reduced TBN has the potential to enhance the transmission of light and reduce the consumption of nutrients, which should ultimately result in increased yield. Consequently, the TBN has emerged as a vital target trait in contemporary breeding programs that focus on compact maize varieties. In this study, QTL-seq technology and advanced population mapping were used to rapidly identify and dissect the major effects of the TBN on QTL. Advanced mapping populations (BC₄F₂ and BC₄F₃) were derived from the inbred lines 18–599 (8–11 TBN) and 3237 (0–1 TBN) through phenotypic recurrent selection. First, 13 genomic regions associated with the TBN were detected using quantitative trait locus (QTL)-seq and were located on chromosomes 2 and 5. Subsequently, validated loci within these regions were identified by QTL-seq. Three QTLs for TBN were identified in the BC₄F₂ populations by traditional QTL mapping, with each QTL explaining the phenotypic variation of 6.13–18.17%. In addition, for the major QTL (qTBN2-2 and qTBN5-1), residual heterozygous lines (RHLs) were developed from the BC₄F₂ population. These two major QTLs were verified in the RHLs by QTL mapping, with the phenotypic variation explained (PVE) of 21.57% and 30.75%, respectively. Near-isogenic lines (NILs) of qTBN2-2 and qTBN5-1 were constructed. There were significant differences between the NILs in TBN. These results will enhance our understanding of the genetic basis of TBN and provide a solid foundation for the fine-mapping of TBN.

雄穗与穗争夺养分，遮挡上部叶片，从而降低籽粒产量。雄穗分枝数（TBN）是雄穗大小的关键决定因素，其中减少的TBN有可能增强光的传输并减少养分的消耗，这最终应导致产量增加。因此，TBN 已成为当代紧凑型玉米品种育种计划中的一个重要目标性状。在这项研究中，QTL-seq技术和先进的群体作图被用来快速识别和剖析TBN对QTL的主要影响。高级作图群体（BC ₄ F ₂和BC ₄ F ₃）是通过表型轮回选择从自交系18-599 (8-11 TBN) 和3237 (0-1 TBN) 衍生而来。首先，使用数量性状基因座 (QTL)-seq 检测到与 TBN 相关的 13 个基因组区域，这些区域位于 2 号和 5 号染色体上。随后，通过 QTL-seq 鉴定了这些区域内经过验证的基因座。通过传统的QTL作图，在BC ₄ F ₂群体中鉴定出了TBN的3个QTL，每个QTL解释了6.13-18.17%的表型变异。此外，对于主要QTL（qTBN2-2和qTBN5-1），从BC ₄ F ₂群体中开发了残余杂合系（RHL）。通过QTL作图在RHL中验证了这两个主要QTL，表型变异解释率（PVE）分别为21.57%和30.75%。构建了qTBN2-2和qTBN5-1的近等基因系 (NIL) 。TBN 中的 NIL 之间存在显着差异。这些结果将增强我们对TBN遗传基础的理解，并为TBN的精细定位提供坚实的基础。