Jarret R L, Merrick L C, Holms T, Evans J, Aradhya M K
United States Department of Agriculture, Agricultural Research Service, Plant Genetic Resources, Griffin, GA 30223, USA.
Genome. 1997 Aug;40(4):433-41. doi: 10.1139/g97-058.
Simple sequence repeat length polymorphisms were utilized to examine genetic relatedness among accessions of watermelon (Citrullus lanatus (Thunb.) Matsum. & Nakai). A size-fractionated TaqI genomic library was screened for the occurrence of dimer and trimer simple sequence repeats (SSRs). A total of 96 (0.53%) SSR-bearing clones were identified and the inserts from 50 of these were sequenced. The dinucleotide repeats (CT)n and (GA)n accounted for 82% of the SSRs sequenced. PCR primer pairs flanking seven SSR loci were used to amplify SSRs from 32 morphologically variable watermelon genotypes from Africa, Europe, Asia, and Mexico and a single accession of Citrullus colocynthis from Chad. Cluster analysis of SSR length polymorphisms delineated 4 groups at the 25% level of genetic similarity. The largest group contained C. lanatus var. lanatus accessions. The second largest group contained only wild and cultivated "citron"-type or C. lanatus var. citroides accessions. The third group contained an accession tentatively identified as C. lanatus var. lanatus but which perhaps is a hybrid between C. lanatus var. lanatus and C. lanatus var. citroides. The fourth group consisted of a single accession identified as C. colocynthis. "Egusi"-type watermelons from Nigeria grouped with C. lanatus var. lanatus. The use of SSRs for watermelon germplasm characterization and genetic diversity studies is discussed.
利用简单序列重复长度多态性来检测西瓜（Citrullus lanatus (Thunb.) Matsum. & Nakai）种质资源之间的遗传相关性。对一个大小分级的TaqI基因组文库进行筛选，以检测二聚体和三聚体简单序列重复（SSR）的存在。共鉴定出96个（0.53%）携带SSR的克隆，并对其中50个克隆的插入片段进行了测序。二核苷酸重复序列（CT）n和（GA）n占测序SSR的82%。使用侧翼位于7个SSR位点的PCR引物对，从来自非洲、欧洲、亚洲和墨西哥的32个形态各异的西瓜基因型以及来自乍得的一个Citrullus colocynthis单份种质中扩增SSR。SSR长度多态性的聚类分析在25%的遗传相似性水平上划分出4个组。最大的组包含C. lanatus var. lanatus种质。第二大组仅包含野生和栽培的“香瓜”类型或C. lanatus var. citroides种质。第三组包含一个暂时鉴定为C. lanatus var. lanatus但可能是C. lanatus var. lanatus和C. lanatus var. citroides之间杂交种的种质。第四组由一个鉴定为C. colocynthis的单份种质组成。来自尼日利亚的“埃古西”型西瓜与C. lanatus var. lanatus聚类在一起。文中讨论了SSR在西瓜种质鉴定和遗传多样性研究中的应用。
