Abstract The planting density of broccoli can directly affect the yield and overall health of plants. Nonetheless, studies on the genetic base of planting density in broccoli are rather limited. In this study, the important planting density-dependent factors of broccoli, plant height (PH), maximum outer petiole length (PL) and leaf width (LW), were investigated during 2017 and 2018. In this study, mapping of QTL for PH, PL and LW based on a DH population in broccoli, and as well as the interaction between QTLs and the environment. The DH population was constructed with 176 genotypes obtained from F1 hybrid produced by crossing two different inbred lines 86101 (P1) and 90196 (P2). In our study, a linkage group including a total of 438 SSR markers were constructed covering a length of 1168.26 cM using QTL IciMapping 4.0 software. Finally, there were mainly four QTLs (phc1, phc2, phc4−2, phc4−3), one QTL (plc6−2), and two QTLs (lwc1, lwc3−1) corresponding for PH, PL and LW recurred during the two years. In three environments, inclusive composite interval mapping (ICIM) analysis showed that there was a major QTL for PH at 7.20 cM on chromosome 1 with a high explanatory contribution rate of 20.05 %. The QTL at the 11.10 cM position of chromosome 6 was located for the PL with a high explanatory contribution rate of 20.02 %. The QTL at the 147.00 cM position of chromosome 3 was located on LW with a high explanatory contribution rate of 19.97 %. Interestingly, we found an overlap region (pplc4) in the chromosome 4 containing three QLTs for traits PH, PL, and LW (phc4−2, plc4−3, and lwc4−2). According to this study, the possible positions of candidate genes were screened to provide a basis for further locating and cloning genes for plant height, maximum outer petiole and leaf width, which would be beneficial to breeding of broccoli and the Brassica crops, especially in high planting density.

中文翻译：

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西兰花双二倍体群体种植密度性状QTL定位

摘要 西兰花的种植密度直接影响植物的产量和整体健康。尽管如此，关于西兰花种植密度遗传基础的研究相当有限。本研究在 2017 年和 2018 年期间调查了西兰花的重要种植密度依赖性因素、株高 (PH)、最大外叶柄长度 (PL) 和叶宽 (LW)。 , PL 和 LW 基于西兰花中的 DH 种群，以及 QTL 与环境之间的相互作用。DH 群体是用 176 个基因型构建的，这些基因型来自 F1 杂种，通过杂交两个不同的自交系​​ 86101 (P1) 和 90196 (P2) 产生。在我们的研究中，使用 QTL IciMapping 4.0 软件构建了一个连锁群，包括总共 438 个 SSR 标记，覆盖长度为 1168.26 cM。最后，两年内主要有4个QTLs（phc1、phc2、phc4-2、phc4-3）、1个QTLs（plc6-2）和2个与PH、PL和LW对应的QTLs（lwc1、lwc3-1）出现。在三种环境中，包容性复合区间作图（ICIM）分析表明，1号染色体上存在7.20 cM处PH的主要QTL，解释贡献率高达20.05%。6号染色体11.10cM位置的QTL定位于PL，解释贡献率高达20.02%。3号染色体147.00cM位置的QTL位于LW上，解释贡献率高达19.97%。有趣的是，我们在 4 号染色体中发现了一个重叠区域 (pplc4)，其中包含 PH、PL 和 LW 性状的三个 QLT（phc4-2、plc4-3 和 lwc4-2）。根据这项研究，