小麦EST-SSRs分子标记的特性及其遗传作图(英文)

Investigation of Characteristics and Polymorphism of Wheat EST-SSRs and Their Genetic Mapping

为了解普通小麦EST来源的微卫星的多样性,从大约1 000个包含微卫星的ESTs中设计了300对引物,研究和评估了它们的多态性水平,并且将多态性标记加入到现有的遗传图谱中。在五种不同类型的重复单元中,三个碱基的重复单元出现最多,占到77%。几乎所有的EST-SSRs标记(99.3%)的重复单元都含有G-C碱基对。37.4%的微卫星都是四次重复。对于扩增和多态性,300对引物中有60对没有扩增,21.3%的扩增引物没能产生预期的扩增片断。58%的标记至少在所用8个材料的一个中显示出多态性。W7984和Opata组合表现出最高的多态性水平。大多数普通小麦EST-SSRs标记的重复次数小于10,并且4次重复是最为普遍的。81个新的EST-SSR位点被添加到两个已有的参照遗传图谱中(62个加到ITMI,19个加到CTCS)。研究结果表明小麦EST-SSRs标记展示了一些不同于基因组微卫星的特异特征,在标记发展和其他遗传应用中,这就使得它们能够成为一种非常有价值的资源。

Recently, EST-derived SSRs has become an attractive alternative to complement existing SSR collections in several important crops. However, the information on the occurrence and composi tion of different SSRs will be important for using them as a source for marker development and other application. In this study, 300 pairs of primers were designed from about 1000 wheat ESTs containing a microsatellite to investigate diversity and characteristics of EST-derived SSRs in wheat （Triticum aestivum）, to assess their polymorphism and to integrate polymorphic markers into the reference ge netic maps. Among the five different classes of repeated motif, the trinuleotide repeats were the most frequent （77%）. Almost all of EST-SSRs （99.33%） contained G-C basepairs at the repeated motif. The SSRs mainly contained four repeats （37.4%）. With respect to amplification and polymorphism, 60 of 300 primer pairs failed to amplify and 21.3% of the remaining did not yield fragments of the expected size. 139 （58%） of the 240 markers giving an amplification product showed polymorphism on at least one of the eight cultivars used. The crossW7984×Opata （37.5%） showed the most polymorphic. Most wheat EST -SSRs were shorter than 10 repeat units and four units were most frequent. Eighty one new EST-SSR loci were integrated to the two reference genetic maps currently used in the lab （62 onITMI and 19 on CtCS maps）. Our results showed that wheat EST-SSRs markers exhibited some interesting features, different from those of genomic SSRs. This makes them highly valuable as a source for marker development as well as other applications.