Abstract: Expressed Sequence Tags(ESTs) are a source of simple sequence repeats(SSRs) that can be used to develop molecular markers for genetic studies． The object of the present study is to develop EST-SSR markers from Cucurbitaand uses these markers in quickly purity testing of F₁hybrid seed． The availability of 1457 ESTs for Cucurbita，which documented in GenBank，provided a unique opportunity to develop EST-SSR markers，and 215 SSRs were identified among these non-redundant EST sequences． These SSRs contained 2-6 bp nucleotide motifs including 111 different motif types． The trinucleotide repeat is the dominant type，accounting for 40% with 86 motifs， a nd the frequency of occurrence of dinucleotide repeat is 28． 84% with 62 motifs． Among these motifs，CT motif (21，9 ． 77%) was the most common type，and then were TC and AAG motifs，accounting for 6． 05% and 5． 58%， respectively． A total of 215 primer pairs were designed and 43 of them were synthesized and used to determine their usability by amplification in 4 Cucurbitainbred lines． The results show that 28 of them could successfully amplify， accounting for 65． 12% of testing primer pairs． Then these primer pairs were used to test the F₁hybrid seed purity in Cucurbita． Seed genetic purity from 13 combinations ranged from 79． 2% to 100． 0%，which were in high accordance with those from field grow-out trials． Taken together， this study reported an effective and feasible approach to develop SSR markers for Cucurbita，and demonstrated their usefulness in purity testing of hybrid squash seed．

Key words: Cucurbita, EST-SSR, Marker development, Hybrid seed purity

CLC Number: 

• S642． 1