Department of Crop and Soil Sciences, Washington State University, Pullman, WA 99164, USA.
J Hered. 2011 Jan-Feb;102(1):17-28. doi: 10.1093/jhered/esq103. Epub 2010 Dec 10.
Prickly lettuce (Lactuca serriola L.) is a problematic weed of Pacific Northwest and recently developed resistance to the auxinic herbicide 2,4-D. There are no publically available simple sequence repeat (SSR) markers to tag 2,4-D resistance genes in L. serriola. Therefore, a study was conducted to develop SSR markers from expressed sequence tags (ESTs) of 5 Lactuca species. A total of 15,970 SSRs were identified among 57,126 EST assemblies belonging to 5 Lactuca species. SSR-containing ESTs (SSR-ESTs) ranged from 6.23% to 7.87%, and SSR densities ranged from 1.28 to 2.51 kb(-1) among the ESTs of 5 Lactuca species. Trinucleotide repeats were the most abundant SSRs detected during the study. As a representative sample, 45 ESTs carrying class I SSRs (≥ 20 nucleotides) were selected for designing primers and were also searched against the dbEST entries for L. sativa and Helianthus annuus (≤ 10(-50); score ≥ 100). In silico analysis of 45 SSR-ESTs showed 82% conservation across species and 68% conservation across genera. Primer pairs synthesized for the above 45 EST-SSRs were used to study genetic diversity among a collection of 22 L. serriola biotypes. Comparison of the resultant dendrogram to that developed using phenotypic evaluation of the same subset of lines showed limited correspondence. Taken together, this study reported a collection of useful SSR markers for L. serriola, confirmed transferability of these markers within and across genera, and demonstrated their usefulness in studying genetic diversity.
刺山柑（Lactuca serriola L.）是北美太平洋西北地区的一种有害杂草，最近对生长素除草剂 2,4-D 产生了抗性。目前还没有公开的简单重复序列（SSR）标记可用于标记 L. serriola 中的 2,4-D 抗性基因。因此，进行了一项研究，旨在从 5 种莴苣属植物的表达序列标签（EST）中开发 SSR 标记。在属于 5 种莴苣属植物的 57126 个 EST 组装中，共鉴定出 15970 个 SSR。含有 SSR 的 EST（SSR-EST）的范围为 6.23％至 7.87％，SSR 密度的范围为 5 种莴苣属植物的 EST 中的 1.28 至 2.51 kb（-1）。三核苷酸重复是本研究中检测到的最丰富的 SSR。作为代表性样本，选择了 45 个携带 I 类 SSR（≥20 个核苷酸）的 EST 用于设计引物，并在 dbEST 中搜索了 L. sativa 和 Helianthus annuus 的条目（≤10（-50）；得分≥100）。对 45 个 SSR-EST 的计算机分析表明，物种间有 82％的一致性，属间有 68％的一致性。为上述 45 个 EST-SSR 合成的引物对用于研究 22 个 L. serriola 生物型的遗传多样性。将所得的聚类图与同一亚组系进行表型评估所得到的聚类图进行比较，显示出有限的对应关系。总的来说，本研究报告了一系列对 L. serriola 有用的 SSR 标记，证实了这些标记在属内和属间的可转移性，并证明了它们在研究遗传多样性中的有用性。
