甜瓜EST-SSR位点信息及标记开发

 对GenBank中35 547条甜瓜EST进行净化处理, 得到总长度为2.5 ×10⁷ bp 的无冗余EST34 408条。从这些序列中发现2 877 个SSR, 分布于2 119 条EST中, 出现频率为8.36% , 分布密度为1/8.72 kb。单碱基、二碱基和三碱基重复是主导重复类型, 分别占EST2SSR总数的16.61%、22.49%和46.09%。A /T、AG/CT和AAG/CTT分别是单碱基、二碱基和三碱基的优势重复基元, 分别占15.88%、16.02%和28.61%。在所有的EST-SSR中, 69.10%的重复次数为4～10次, 51.34%的长度为12～20 bp。设计了30对EST-SSR引物, 分别对33份甜瓜自交系进行了PCR扩增, 24对引物能够扩增出期望长度的条带, 22对引物产物表现多态性, 平均每对引物能检测到2.73个等位基因。这些引物能比较准确地将甜瓜材料聚为不同类别。24对引物中, 有19对、16对和15对分别在黄瓜、西瓜和葫芦中通用。以上结果说明, 从甜瓜EST中开发SSR标记是一条简便、可行的途径。

Information on EST-SSR Loci in Melon (Cucumis melo L.) and Marker Exploitation

A total of 35 547 melon ESTswere downloaded from GenBank (http: www.ncbi.nlm.nih.gov) and cleaned resulting in production of 34 408 non-redundant ESTs with a total length of 215 ×107 bp. From these sequences, 2 877 SSRs were sought out, distributing in 2 119 ESTs. The frequency of the EST2SSRs was 8.36% and mean distance was 8.72 kb in 34 408 ESTs. Mononucleotide, dinucleotide and trinucleotide repeats were major types, respectively accounting for 16.61% , 22.49% and 46.09%. A /T, AG/CT andAAG/CTT were most frequent motifs in mononucleotide, dinucleotide and trinucleotide, accounting for 15.88% , 16.02% and 28.61% , respectively. The frequency of the EST2SSRswith a repeat number of 4 -10 was 69.10% and 51.34% of them had a length of 12 - 20 bp. Thirty p rimer pairswere designed for partial EST-SSRs and used for PCR amp lification of 33 melon inbred lines. Among the p rimer pairs, 24 pairs gave distinct bands with expected length and 22 pairs generated polymorphic bands with 2.73 alleles per primer pair. With the primers, melon materials could be exactly divided into different groups, which accorded with the actual situation of the materials. Among the 24 p rimer pairs, 19 pairs could be transferable to cucumber and 16 pairs to watermelon and 15 pairs to gourd. All these results indicated that exp loitation of SSR markers from melon ESTs was convenient and p racticable.