OBJECTIVETo establish the EST-SSR marker system for Cordyceps by using ESTs of C. bassiana and C. militaris.

METHODThe ESTs of Cordyceps were downloaded from the public database of NCBI, and the redundant ESTs with low quality were removed. The EST-SSR primers were designed by Sequece Seiner 1. 2. And the primers were screened through PAGE-Electrophoresis.

RESULTThe 4 556 non-redundant ESTs which from C. bassiana with total length of 2 953 173 bp were selected. 718 EST-SSRs distributed in 616 ESTs were totally screened out, accounting for 15.8% of the non-redundant ESTs. It was discovered that the average distance of EST-SSSR was 1/4 096 bp in EST-SSRs distribution of C. bassiana. Trinucleotide repeats were the most abundant types with 419 repeated sequences. Regarding to C. militaris, totally 1 363 non-redundant ESTs were acquired, from which 1 117 EST-SSRs were screened, and rate of SSR sites in ESTs was 81.95%. The leading motif of SSR was nucleotide A. The 50 pairs of EST-SSR primers were designed according to the ESTs of C. bassiana, and preliminary test showed the 34 pairs of primers amplified clear fragments,accounting for 68% of all primers. Furthermore, the 39 of the 40 pairs of primers from the ESTs of C. militaris were found to be amplified as the clear fragments, accounting for 97.5%. The phylogenetic analysis revealed that different anamorph of Cordyceps spieces were divided into four branches.

CONCLUSIONThe EST-SSR of Cordyceps had comparably higher utility value. The EST-SSR markers developed from ESTs of C. bassiana and C. militaris had well transferability in Cordyceps. And it was suggested that the EST-SSR markers should be an easy and effective way to assay molecular genetic structure of Cordyceps.