Abstract:

We extracted DNA from 20 infected plants and their healthy counterparts collected in China, amplified the phytoplasma 16S rDNA fragments by nested PCR.The primer pair R16F2/R16R2 amplified a 16S rDNA fragment (about 1.2kb) from each DNA sample prepared from 20 infected tissues but not from any DNA sample extracted from healthy tissues. We purified the nested PCR products and connected it into T-vector for storage.The 16S rDNA fragments amplified were compared through RFLP analysis. Based on the similarity of RFLP patterns, these 20 phytoplasmas could be classified into 4 distinct 16S ribosomal RNA groups, corresponding to: Aster yellows (Paulownia witches'-broom, Hackberry witches' - broom, Periwinkle witches'-broom, Fernleaf hedge bamboo witches'-broom, Hibiscus fasciated disease, Chinaberry tree witches'-broom, Chinese thorny bamboo witches' -broom, Tobacco witches' broom, Banana bunchy top, Everg reen chinkapin witches'-broom, Willow yellows, Mulberry yellow dwarf disease, Mulberry dwarf disease); Ash yellows(Cherry fasciated disease, Jujube witches'-broom); Peanut witches' -broom (Stylosanthes gracilis H. B. K. witches'-broom, Groundnut witches' -broom, Stylosanthes guianensis cv. Witches' - broom) and clover proliferation (Bishopwood witches'-broom, Cinnamon yellows).

Key words: Phytoplasma, 16S rDNA, Nested PCR, RFLP