Red tilapia ( Oreochromis spp .) is one of the most popular fish in China due to its bright red appearance, fast growth rate, and strong adaptability. Understanding the sex determination mechanisms is of vital importance for the selection of all-male lines to increase aquacultural production of red tilapia. In this research, the genetic architecture for sex from four mapping populations ( n=1 090) of red tilapia was analyzed by quantitative trait loci (QTL)-seq, linkage-based QTL mapping, and linkage disequilibrium (LD)-based genome-wide association studies. Two genome-wide significant QTL intervals associated with sex were identified on ChrLG1 (22.4-23.9 Mb) and ChrLG23 (32.0-35.9 Mb), respectively. The QTL on ChrLG1 was detected in family 1 (FAM1), FAM2, and FAM4, and the other QTL on ChrLG23 was detected in FAM3 and FAM4. Four microsatellite markers located within the QTL were successfully developed for marker-assisted selection. Interestingly, three ( lpp, sox14, and amh) of the 12 candidate genes located near or on the two QTL intervals were abundantly expressed in males, while the remaining genes were more highly expressed in females. Seven genes ( scly, ube3a, lpp, gpr17, oca2, cog4, and atp10a) were significantly differentially expressed between the male and female groups. Furthermore, LD block analysis suggested that a cluster of genes on ChrLG23 may participate in regulating sex development in red tilapia. Our study provides important information on the genetic architecture of sex in red tilapia and should facilitate further exploration of sex determination mechanisms in this species.
红罗非鱼（ Oreochromis spp.）体色呈鲜红色，生长速度快，适应性强，是广受欢迎的经济鱼类之一。探究其性别决定机制对于选育全雄品系，增加红罗非鱼的水产养殖产量至关重要。该研究综合应用QTL-seq、基于连锁图谱的QTL定位以及基于连锁不平衡（LD）的全基因组关联分析方法，对4个不同群体（FAM1、FAM2、FAM3、FAM4， n=1 090）的性别遗传机制进行了解析。我们鉴定出了两个基因组水平与性别性状显著相关的QTL 区间，分别位于ChrLG1 （22.4–23.9 Mb） 和 ChrLG23 （32.0–35.9 Mb）。在FAM1、FAM2 和 FAM4 群体中，检测到了一个位于ChrLG1 上的主效QTL，而在FAM3 和 FAM4 中检测到了一个位于ChrLG23 上的主效QTL。在两个QTL区间内，成功开发了四个可用于标记辅助选择育种的微卫星标记。对位于两个 QTL 区间内或临近区域的 12 个候选基因进行表达验证，结果显示其中三个基因（ lpp、 sox14 和 amh）在雄性中表达量更高，而其余基因则在雌性中具有更高表达，有7 个基因（ scly、 ube3a、 lpp、 gpr17、 oca2、 cog4 和 atp10a）在雌雄性腺中存在显著差异表达。LD 区块分析表明 ChrLG23 上可能存在一个基因簇共同参与调控了红罗非鱼的性别发育。该研究为开展红罗非鱼全雄品系的分子选育及深入探究其性别的分子遗传机制提供了重要数据。.
Keywords: QTL mapping; Red tilapia; SNPs; Sex.