United States Department of Agriculture, Agricultural Research Service, U.S. Agricultural Research Station, Salinas, CA 93905, USA.
BMC Plant Biol. 2013 Jan 22;13:11. doi: 10.1186/1471-2229-13-11.
Lettuce (Lactuca sativa L.) is the major crop from the group of leafy vegetables. Several types of molecular markers were developed that are effectively used in lettuce breeding and genetic studies. However only a very limited number of microsattelite-based markers are publicly available. We have employed the method of enriched microsatellite libraries to develop 97 genomic SSR markers.
Testing of newly developed markers on a set of 36 Lactuca accession (33 L. sativa, and one of each L. serriola L., L. saligna L., and L. virosa L.) revealed that both the genetic heterozygosity (UHe = 0.56) and the number of loci per SSR (Na = 5.50) are significantly higher for genomic SSR markers than for previously developed EST-based SSR markers (UHe = 0.32, Na = 3.56). Fifty-four genomic SSR markers were placed on the molecular linkage map of lettuce. Distribution of markers in the genome appeared to be random, with the exception of possible cluster on linkage group 6. Any combination of 32 genomic SSRs was able to distinguish genotypes of all 36 accessions. Fourteen of newly developed SSR markers originate from fragments with high sequence similarity to resistance gene candidates (RGCs) and RGC pseudogenes. Analysis of molecular variance (AMOVA) of L. sativa accessions showed that approximately 3% of genetic diversity was within accessions, 79% among accessions, and 18% among horticultural types.
The newly developed genomic SSR markers were added to the pool of previously developed EST-SSRs markers. These two types of SSR-based markers provide useful tools for lettuce cultivar fingerprinting, development of integrated molecular linkage maps, and mapping of genes.
生菜（Lactuca sativa L.）是叶菜类蔬菜的主要作物。已经开发出几种类型的分子标记，这些标记有效地用于生菜的育种和遗传研究。然而，只有非常有限数量的微卫星标记是公开可用的。我们采用富集微卫星文库的方法开发了 97 个基因组 SSR 标记。
在一组 36 个生菜品种（33 个 L. sativa 品种，1 个 L. serriola L.、L. saligna L. 和 L. virosa L.）上测试新开发的标记，结果表明基因组 SSR 标记的遗传杂合度（UHe=0.56）和每个 SSR 的标记数（Na=5.50）均显著高于先前开发的基于 EST 的 SSR 标记（UHe=0.32，Na=3.56）。54 个基因组 SSR 标记被定位在生菜的分子连锁图谱上。标记在基因组中的分布似乎是随机的，除了连锁群 6 上可能存在的簇。任何 32 个基因组 SSR 的组合都能够区分所有 36 个品种的基因型。新开发的 14 个 SSR 标记源自与抗性基因候选物（RGC）和 RGC 假基因具有高序列相似性的片段。对 L. sativa 品种的分子方差分析（AMOVA）表明，遗传多样性的约 3%存在于品种内，79%存在于品种间，18%存在于园艺类型间。
新开发的基因组 SSR 标记已添加到先前开发的 EST-SSR 标记库中。这两种基于 SSR 的标记为生菜品种指纹图谱、综合分子连锁图谱的构建以及基因图谱的构建提供了有用的工具。
