Institute for Agricultural and Fisheries Research (ILVO), Plant Sciences Unit, Caritasstraat 21, 9090 Melle, Belgium.
BMC Mol Biol. 2010 Jan 13;11:1. doi: 10.1186/1471-2199-11-1.
Azalea (Rhododendron simsii hybrids) is the most important flowering pot plant produced in Belgium, being exported world-wide. In the breeding program, flower color is the main feature for selection, only in later stages cultivation related plant quality traits are evaluated. As a result, plants with attractive flowering are kept too long in the breeding cycle. The inheritance of flower color has been well studied; information on the heritability of cultivation related quality traits is lacking. For this purpose, QTL mapping in diverse genetic backgrounds appeared to be a must and therefore 4 mapping populations were made and analyzed.
An integrated framework map on four individual linkage maps in Rhododendron simsii hybrids was constructed. For genotyping, mainly dominant scored AFLP (on average 364 per population) and MYB-based markers (15) were combined with co-dominant SSR (23) and EST markers (12). Linkage groups were estimated in JoinMap. A consensus grouping for the 4 mapping populations was made and applied in each individual mapping population. Finally, 16 stable linkage groups were set for the 4 populations; the azalea chromosome number being 13. A combination of regression mapping (JoinMap) and multipoint-likelihood maximization (Carthagène) enabled the construction of 4 maps and their alignment. A large portion of loci (43%) was common to at least two populations and could therefore serve as bridging markers. The different steps taken for map optimization and integration into a reference framework map for QTL mapping are discussed.
This is the first map of azalea up to our knowledge. AFLP and SSR markers are used as a reference backbone and functional markers (EST and MYB) were added as candidate genes for QTL analysis. The alignment of the 4 maps on the basis of framework markers will facilitate in turn the alignment of QTL regions detected in each of the populations. The approach we took is thoroughly different than the recently published integrated maps and well-suited for mapping in a non-model crop.
映山红（Rhododendron simsii 杂种）是比利时最重要的开花盆栽植物，出口到世界各地。在育种计划中，花色是选择的主要特征，只有在后期才会评估与栽培相关的植物质量特性。因此，具有吸引力的开花植物在育种周期中保留时间过长。花色的遗传已经得到了很好的研究；与栽培相关的质量特性的遗传力信息却缺乏。为此，在不同的遗传背景下进行 QTL 作图似乎是必要的，因此制作并分析了 4 个作图群体。
构建了映山红杂种的 4 个个体连锁图谱的综合框架图谱。用于基因型分析的主要是显性标记 AFLP（平均每个群体 364 个）和基于 MYB 的标记（15 个），同时结合了共显性 SSR（23 个）和 EST 标记（12 个）。在 JoinMap 中估计了连锁群。对 4 个作图群体进行了共识分组，并应用于每个个体作图群体。最终，4 个群体设定了 16 个稳定的连锁群；映山红的染色体数为 13 条。回归作图（JoinMap）和多点似然最大化（Carthagène）的组合能够构建 4 个图谱并进行图谱对齐。至少有两个群体共有的大部分（43%）位点可作为桥接标记。讨论了图谱优化和整合到 QTL 作图参考框架图谱的不同步骤。
这是迄今为止映山红的第一张图谱。AFLP 和 SSR 标记被用作参考骨干，同时添加了功能标记（EST 和 MYB）作为 QTL 分析的候选基因。基于框架标记对 4 个图谱的对齐反过来将有助于在每个群体中检测到的 QTL 区域的对齐。我们采用的方法与最近发表的整合图谱有很大的不同，非常适合非模式作物的作图。
