Detection and identification of a novel subgroup 16SrII-V phytoplasma associated with Praxelis clematidea phyllody disease

Praxelis clematidea is a very vigorous non-native weed in tropical and subtropical regions of China. P. clematidea plants showing symptoms of phyllody disease were found in an orchard located in Hainan province, PR China. The presence of phytoplasmas was confirmed by PCR of 16S rRNA gene using phytoplasma universal primers R16mF2/R16mR1 followed by R16F2n/R16R2. According to 16S rRNA gene sequence similarity, the P. clematidea phyllody (PCP) phytoplasma is a 'Candidatus Phytoplasma australasiae'-related strain (99.5% similarity). The virtual RFLP pattern analyses of 16S rRNA gene sequences indicated that the PCP is a new subgroup within 16 Sr group II. The most similar RFLP pattern is the reference pattern of 16Sr group II, subgroup M, with a similarity coefficient of 0.94. These results were confirmed by phylogenetic analyses of the 16S rRNA gene. These findings suggest that P. clematidea phyllody disease is caused by a new phytoplasma considered to be a novel subgroup, 16SrII-V.