Abstract: In the present study， ITS sequences were cloned from 24 Dendrobium plants， and were analyzed by bioinformatics software to provide evidences for molecular identification and genetic diversity study. The full ITS sequences of 24 plants ranged from 634-646 bp in length. Sequences of 58S were conserved with the same length of 164 bp， while ITS1 and ITS2 were more variable with lengths of 226-235 bp and 241-247 bp， respectively. Variable sites were rich in ITS1 and ITS2 sequences， as there were 176 and 166 variable sites with 114 and 104 parsimony information sites， respectively， and many transitions， transversions， and deletions/insertions were observed. However， 58S sequences were more conserved， and there were 36 variable sites and 16 parsimony information sites. It was shown that ITS sequences could be used to distinguish all 24 Dendrobium plants studied here. The genetic distance of 24 Dendrobium plants ranged from 0007 to 0302. The smallest genetic distance was observed between D. chrysotoxum and D. chrysotoxum var. suavissimum revealing their closest relationship， while the largest genetic distance was determined between D. hookerianum and D. capillipes uncovering their distinct relationship.

Key words: Dendrobium, ITS sequence, cloning, molecular identification