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Comparison of 16S rDNA and 16S/23S Intergenic Region Sequences Among Citrus Greening Organisms in Asia

Polymerase chain reaction was used to amplify and sequence the 16S ribosomal RNA gene (rDNA) and 16S/23S intergenic region of several isolates of citrus greening organism (GO) from Japan, the Philippines, Indonesia, and Thailand. The sequences of 16S rDNA were identical among all the isolates studied, very similar to the published sequences of Thai (99.4 to 100% identity), Nepalese (100% identity), and Indian (98.8% identity) strains, and less similar to an African strain (97.5% identity). The sequences of the intergenic region between 16S and 23S rDNA were also identical among the isolates examined as well as the reported Nepalese and Thai isolates. They were close to the sequences of reported strains of India and China (99.2%) and apart from those of the African strain (85.5%). These results suggested that some isolates of GO from Japan, the Philippines, Indonesia, Thailand, and Nepal constitute one strain, which is similar to Indian and Chinese strains and distinct from the African strain.