Tassel branch number (TBN) is the principal component of tassel inflorescence architecture in the maize plant. TBN is believed to be controlled by a set of quantitative trait loci (QTLs). However, it is necessary to identify and genetically evaluate these QTLs before the TBN can be improved upon using a molecular breeding approach. Therefore, in this study, we developed the chromosome segment introgression line (CSIL) TBN1 with the Zong31 (Z31) background and a higher TBN, and then we utilized the CSIL-TBN1-derived populations and identified a major QTL, qTBN6a, by linkage analysis. Fine mapping of the qTBN6a QTL was validated using a set of sub-CSILs and located in a 240-kb genomic region (Bin6.07) in B73RefGen_v4. One allele included in the introgression fragment had a positive effect, noticeably increasing the TBN and demonstrating the potential to improve the TBN of Z31. Afterward, in the qTBN6a interval, gene expression, sequence alignment, functional analysis, and the analysis of motifs in the 5′ UTR suggested that candidate genes of qTBN6a are important functional genes at the early stage of immature infected tassel development. Among these candidate genes, a long W22::Mu-insertion/deletion in exon one and an 11-bp insertion/deletion in the promoter region may affect the variation of the qTBN6a QTL observed between Z31 and TBN1. In addition, the candidate genes of qTBN6a were found to encode a pentatricopeptide repeat (PPR)-containing protein and a histone deacetylase (HDA), which are known to be closely associated with RNA editing and stability and chromatin state activity for the transcription of gene expression, respectively. Finally, a model of qTBN6a based on the synergistic regulation of PPR and HDA for the maintenance of inflorescence meristem (IM) identity and its differentiation to the branch meristem (BM) in TBN1 was suggested. Collectively, our results provide an available locus for the molecular improvement of TBN and the isolation of functional genes underlying this QTL.

s穗分支编号（TBN）是玉米植物plant穗花序结构的主要组成部分。TBN被认为是由一组数量性状基因座（QTL）控制的。但是，在使用分子育种方法改善TBN之前，有必要鉴定和遗传评估这些QTL。因此，在这项研究中，我们开发了具有Zong31（Z31）背景和更高TBN的染色体区段基因渗入系（CSIL）TBN1，然后我们利用CSIL-TBN1衍生的种群并通过连锁鉴定了主要的QTL qTBN6a分析。qTBN6a的精细映射QTL已使用一组亚CSIL进行了验证，并位于B73RefGen_v4的240 kb基因组区域（Bin6.07）中。渗入片段中包含的一个等位基因具有积极作用，明显增加了TBN，并显示了改善Z31 TBN的潜力。之后，在qTBN6a间隔中，基因表达，序列比对，功能分析和5'UTR中的基序分析表明，qTBN6a的候选基因在未成熟的受感染流苏发育的早期是重要的功能基因。在这些候选基因中，外显子一的长W22 :: Mu插入/缺失和启动子区域的11-bp插入/缺失可能影响qTBN6a的变异在Z31和TBN1之间观察到QTL。此外，发现qTBN6a的候选基因编码含有五肽重复序列（PPR）的蛋白质和组蛋白脱乙酰基酶（HDA），已知它们与RNA编辑，基因转录的稳定性和染色质状态活性密切相关。表达式。最后，建立了基于PPR和HDA协同调控的qTBN6a模型建议维持花序分生组织（IM）的身份，并将其分化为TBN1中的分支分生组织（BM）。总的来说，我们的结果为TBN的分子改良和QTL基础功能基因的分离提供了一个可用的基因座。