PHYTOPLASMA-SPECIFIC PCR PRIMERS BASED ON SEQUENCES OF THE 16S-23S RIBOSOMAL-RNA SPACER REGION

In order to develop a diagnostic tool to identify phytoplasmas and cla ssify them according to their phylogenetic group, we took advantage of the sequence diversity of the 16S-23S intergenic spacer regions (SRs) of phytolplasmas. Ten PCR primers were developed from the SR sequence s and were shown to amplify in a group-specific fashion. Far same grou ps of phytoplasmas, such as elm yellows, ash yellows, and pear decline the SR primer nas paired with a specific primer from within the 16S r RNA gene. Each of these primer pairs was specific for a specific phyto plasma group, and they did not produce PCR products of the correct siz e from any other phytoplasma group. One primer was designed to anneal within the conserved tRNA(Ile) and, when paired with a universal prime r, amplified all phytoplasmas tested. None of the primers produced PCR amplification products of the correct size from healthy plant DNA. Th ese primers can serve as effective tools for identifying particular ph ytoplasmas in held samples.