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对GenBank中35547条甜瓜EST进行净化处理,得到总长度为2.5×107bp的无冗余EST34408条。从这些序列中发现2877个SSR,分布于2119条EST中,出现频率为8.36%,分布密度为1/8.72kb。单碱基、二碱基和三碱基重复是主导重复类型,分别占EST-SSR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12～20bp。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。
35547 melon ESTs in GenBank were purified to obtain 2.5 × 107bp non-redundant EST34408. 2877 SSRs were found from these sequences, distributed in 2119 ESTs, with a frequency of 8.36% and a distribution density of 1 / 8.72kb. Single base, two base and three base repeats are dominant repeat types, accounting for 16.61%, 22.49% and 46.09% of the total EST-SSR respectively. A / T, AG / CT and AAG / CTT were the dominant repeat units of single base, two base and three base respectively, accounting for 15.88%, 16.02% and 28.61% respectively. Of all EST-SSRs, 69.10% had 4 to 10 repeats and 51.34% had 12 to 20 bp. Thirty pairs of EST-SSR primers were designed and 33 melon inbred lines were amplified by PCR. Twenty-four pairs of primers were able to amplify the expected bands and 22 pairs of primers showed polymorphism. The average primer- 2.73 alleles were detected. These primers can be more accurately melon materials into different categories. Of the 24 pairs of primers, 19 pairs, 16 pairs and 15 pairs were common in cucumber, watermelon and cucurbit. The above results show that the development of SSR markers from Melon EST is a simple and feasible way.