Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, 88 Xuefu Road, Kunming 650223, PR China.
BMC Plant Biol. 2010 Dec 16;10:278. doi: 10.1186/1471-2229-10-278.
The castor bean (Ricinus communis L.), a monotypic species in the spurge family (Euphorbiaceae, 2n = 20), is an important non-edible oilseed crop widely cultivated in tropical, sub-tropical and temperate countries for its high economic value. Because of the high level of ricinoleic acid (over 85%) in its seed oil, the castor bean seed derivatives are often used in aviation oil, lubricants, nylon, dyes, inks, soaps, adhesive and biodiesel. Due to lack of efficient molecular markers, little is known about the population genetic diversity and the genetic relationships among castor bean germplasm. Efficient and robust molecular markers are increasingly needed for breeding and improving varieties in castor bean. The advent of modern genomics has produced large amounts of publicly available DNA sequence data. In particular, expressed sequence tags (ESTs) provide valuable resources to develop gene-associated SSR markers.
In total, 18,928 publicly available non-redundant castor bean EST sequences, representing approximately 17.03 Mb, were evaluated and 7732 SSR sites in 5,122 ESTs were identified by data mining. Castor bean exhibited considerably high frequency of EST-SSRs. We developed and characterized 118 polymorphic EST-SSR markers from 379 primer pairs flanking repeats by screening 24 castor bean samples collected from different countries. A total of 350 alleles were identified from 118 polymorphic SSR loci, ranging from 2-6 per locus (A) with an average of 2.97. The EST-SSR markers developed displayed moderate gene diversity (He) with an average of 0.41. Genetic relationships among 24 germplasms were investigated using the genotypes of 350 alleles, showing geographic pattern of genotypes across genetic diversity centers of castor bean.
Castor bean EST sequences exhibited considerably high frequency of SSR sites, and were rich resources for developing EST-SSR markers. These EST-SSR markers would be particularly useful for both genetic mapping and population structure analysis, facilitating breeding and crop improvement of castor bean.
蓖麻（Ricinus communis L.）是大戟科（Euphorbiaceae）单种属植物，为重要的非食用油脂作物，因其种子油中蓖麻酸（超过 85%）含量高，而在航空油、润滑剂、尼龙、染料、油墨、肥皂、粘合剂和生物柴油等领域具有较高的经济价值。由于缺乏有效的分子标记，蓖麻种质资源的群体遗传多样性和遗传关系知之甚少。为了在蓖麻中进行有效的品种选育和改良，需要开发更多高效、稳健的分子标记。现代基因组学的发展产生了大量公开可用的 DNA 序列数据。特别是表达序列标签（ESTs）为开发与基因相关的 SSR 标记提供了有价值的资源。
共评估了 18928 个公开的非冗余蓖麻 EST 序列，代表约 17.03Mb，通过数据挖掘共鉴定出 5122 个 EST 中的 7732 个 SSR 位点。蓖麻 EST 中 SSR 出现的频率较高。通过对来自不同国家的 24 个蓖麻样本进行筛选，从 379 对侧翼重复的引物中开发并鉴定了 118 个多态性 EST-SSR 标记。在 118 个多态性 SSR 标记中共鉴定出 350 个等位基因，每个位点 2-6 个（A），平均值为 2.97。开发的 EST-SSR 标记显示出中等的基因多样性（He），平均值为 0.41。利用 350 个等位基因的基因型研究了 24 个种质资源之间的遗传关系，显示出基因型在蓖麻遗传多样性中心的地理模式。
蓖麻 EST 序列中 SSR 位点出现的频率较高，是开发 EST-SSR 标记的丰富资源。这些 EST-SSR 标记将特别有助于遗传图谱构建和群体结构分析，为蓖麻的选育和品种改良提供便利。
