Wheat blue dwarf(WBD)is a disease caused by phytoplasma and only reported from China.A fragment about 1.3 kb in protein translocation gene,secY was amplified by PCR from the total DNA of di-seased wheat sample with primer pair secYF/secYR,which was designed based on secY gene sequence of known 16SrI group members.Nucleotide acid sequence analysis of amplified fragment indicated that the length was 1 240 bp.A phylogenetic tree based on secY gene sequences was constructed and showed that wheat blue dwarf phytoplasma was clustered into the Candidatus Phytoplasma asteris,subgroup 16SrI-C.Wheat blue dwarf phytoplasma showed high homology with clover phyllody phytoplasma strains based on sequence comparison and phylogenetic analysis.
