Jeuken M J W, Pelgrom K, Stam P, Lindhout P
Laboratory of Plant Breeding, Wageningen University, 6700 AJ, Wageningen, The Netherlands.
Theor Appl Genet. 2008 Apr;116(6):845-57. doi: 10.1007/s00122-008-0718-2. Epub 2008 Feb 5.
In plants, several population types [F(2), recombinant inbred lines, backcross inbred lines (BILs), etc.] are used for quantitative trait locus (QTL) analyses. However, dissection of the trait of interest and subsequent confirmation by introgression of QTLs for breeding purposes has not been as successful as that predicted from theoretical calculations. More practical knowledge of different QTL mapping approaches is needed. In this recent study, we describe the detection and mapping of quantitative resistances to downy mildew in a set of 29 BILs of cultivated lettuce (L. sativa) containing genome segments introgressed from wild lettuce (L. saligna). Introgression regions that are associated with quantitative resistance are considered to harbor a QTL. Furthermore, we compare this with results from an already existing F(2) population derived from the same parents. We identified six QTLs in our BIL approach compared to only three in the F(2) approach, while there were two QTLs in common. We performed a simulation study based on our actual data to help us interpret them. This revealed that two newly detected QTLs in the BILs had gone unnoticed in the F(2), due to a combination of recessiveness of the trait and skewed segregation, causing a deficit of the wild species alleles. This study clearly illustrates the added value of extended genetic studies on two different population types (BILs and F(2)) to dissect complex genetic traits.
在植物中，几种群体类型[F(2)、重组自交系、回交自交系（BILs）等]被用于数量性状基因座（QTL）分析。然而，对目标性状的剖析以及随后通过导入QTL进行育种目的的确认，并没有达到理论计算所预测的成功程度。我们需要更多关于不同QTL定位方法的实用知识。在这项最新研究中，我们描述了在一组29个栽培生菜（L. sativa）的BILs中对霜霉病定量抗性的检测和定位，这些BILs包含从野生生菜（L. saligna）导入的基因组片段。与定量抗性相关的导入区域被认为含有一个QTL。此外，我们将此结果与来自同一亲本的现有F(2)群体的结果进行了比较。我们在BIL方法中鉴定出6个QTL，而在F(2)方法中仅鉴定出3个，其中有2个QTL是共有的。我们基于实际数据进行了模拟研究以帮助解读这些结果。这表明，由于性状的隐性和偏分离的组合，导致野生种等位基因缺失，BILs中两个新检测到的QTL在F(2)中未被发现。这项研究清楚地说明了对两种不同群体类型（BILs和F(2)）进行扩展遗传研究以剖析复杂遗传性状的附加价值。
