Abstract:The full-length cDNA of flavonoid-3,5-hydroxylase gene (F3,5H) was cloned by RT-PCR from blue color pedal of Petunia hybrida (GenBank Accession EF371021). Bioinformatics analysis showed that the gene sequence was highly consistent with previously reported F3,5H genes, such as GenBank Accession D14588, Z22545, and DQ352142. The encoded amino acid sequence was highly homology with that of GenBank Accession BAA03438.1 (Petunia hybrida), BAC10997.1 (Nierembergia sp. NB17) and AV85470.1 (Solanum tuberosum) at 99%, 88% and 87%, respectively. A novel vector pBIN19-PchsA-F35H was constructed from plasmids of pBIN19, pBluescript SK(+) and pMD18-PchsA, which was driven by flower-specific promoter of chalcone synthase A gene (PchsA). Furthermore, the vector was successfully transformed into the wild-type Agrobacterium rhizogenes K599. The hairy roots of Dendranthema morifolium were induced by K599 harboring pBIN19-PchsA-F35H with the frequency of 30.7%. The results provided an important foundation for blue flower breeding by gene engineering technique.