deVicente M C, Tanksley S D
Department of Plant Breeding and Biometry, Cornell University, Ithaca, New York 14853.
Genetics. 1993 Jun;134(2):585-96. doi: 10.1093/genetics/134.2.585.
Two accessions, representing the species Lycopersicon esculentum (cultivated tomato) and Lycopersicon pennellii (a wild relative), were evaluated for 11 quantitative traits and found to be significantly different for 10 of the traits. Transgressive segregation was observed for eight of the traits in a large interspecific F2 population. When restriction fragment length polymorphism markers were used as probes for the quantitative trait loci (QTL) underlying the traits, 74 significant QTL (LOD > 2) were detected. Thirty-six percent of those QTL had alleles with effects opposite to those predicted by the parental phenotypes. These QTL were directly related to the appearance of transgressive individuals in the F2 for those traits which showed transgressive segregation. However, the same types of QTL (with allelic effects opposite to those predicted by the parents) were also observed for traits that did not display transgressive segregation in the F2. One such trait was dry weight accumulation. When two overdominant QTL (detected in the F2) for this trait were backcrossed into the L. esculentum genetic background, transgressive individuals were recovered and their occurrence was associated with the two QTL demonstrating the potential for transgressive segregation for all characters and implicating overdominance as a second cause of transgressive segregation. Epistasis was not implicated in transgressive segregation in either the F2 or backcross generations. Results from this research not only reveal the basis of wide-cross transgressive segregation, but demonstrate that molecular markers can be used to identify QTL (from wild species) responsible for transgressive phenotypes and to selectively transfer them into crop species. This strategy might be used to improve many traits of economic importance including those for which wild species appear phenotypically inferior to their cultivated counterparts.
对代表栽培番茄（Lycopersicon esculentum）和野生近缘种潘那利番茄（Lycopersicon pennellii）的两个种质进行了11个数量性状的评估，发现其中10个性状存在显著差异。在一个大型种间F2群体中，观察到8个性状出现了超亲分离。当使用限制性片段长度多态性标记作为这些性状潜在的数量性状基因座（QTL）的探针时，检测到74个显著的QTL（LOD>2）。其中36%的QTL具有与亲本表型预测相反效应的等位基因。这些QTL与F2中出现超亲个体的性状直接相关，这些性状表现出超亲分离。然而，在F2中未表现出超亲分离的性状也观察到了相同类型的QTL（等位基因效应与亲本预测相反）。干物质积累就是这样一个性状。当将该性状在F2中检测到的两个超显性QTL回交至栽培番茄（L. esculentum）的遗传背景中时，获得了超亲个体，它们的出现与这两个QTL相关，这表明所有性状都有超亲分离的潜力，并暗示超显性是超亲分离的第二个原因。上位性在F2或回交世代的超亲分离中未起作用。本研究结果不仅揭示了远缘杂交超亲分离的基础，还表明分子标记可用于鉴定导致超亲表型的（来自野生种的）QTL，并将它们选择性地导入作物品种。该策略可用于改良许多具有经济重要性的性状，包括那些野生种在表型上不如栽培种的性状。
