APS Abstracts of Presentations
Phytoplasma typing based on PCR of 16S rDNA and genetic sequences. E. TUMBAN, J. Rascoe, and M. Shaw. Department of Life Sciences, New Mexico Highlands University, Las Vegas, NM. Phytopathology 92:S82. Publication no. P-2002-0594-AMA. Phytoplasmas have been difficult to classify and characterize because they cannot be grown in axenic culture. Formerly, classification was based entirely on biological characteristics, while current classifications are based almost entirely on 16S ribosomal DNA sequences, exemplified by RFLP analysis or sequencing. A few other genes from specific phytoplasmas have been identified and sequenced. To investigate whether similarities in other genes will confirm phylogenetic relationships based on 16rDNA sequence information, we have used PCR, with either published primers or primers constructed from sequences available in GenBank, to attempt to amplify products from periwinkle plants infected with one of several aster yellows isolates, beet leafhopper virescence agent isolates, or Spiroplasma citri isolates. Primer pairs R16F/ R16R (specific for phytoplasmas) and RPF1/ RPR1 (specific for aster yellows group phytoplasmas) have been used to classify phytoplasmas and were used as positive controls and to confirm group placement. Amplification with the tested primer pairs was generally consistent with group placements made from 16S data.
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