DIFFERENTIATION OF TWO EGYPTIAN ISOLATES OF SPIROPLASMA CITRI BASED ON 16S RDNA, SPIRALIN GENES AND 16S/23S RDNA INTERGENIC SPACER REGIONAYMAN F. OMAR,HABBUDDIN H.KAMARUZAMAN SIJAM, ZANIAL A. M. AHMAD AND OM-HASHEM M. EL-BANNAAbstract Two Egyptian isolates of Spiroplasma citri (Fewa and Qualubia) were studied based on nucleotide sequences of their spiralin and 16S rDNA genes and 16S/23S rDN A in tergenic spacer region sequence. The '16S rDNA of the two isolates comprised 1529 nucleotides with a similarity between them at 99.80% where only two different nucleotides were observed. Both have more than 99.67% similarity to three published strains of S. citri, R.SA2HP, Car4 and Car6. Their 16S/23S rDNA intergenic spacer region has 305 nucleo tides, with a similarity of about 99.76%, where only one nucleotide difference was observed. The 16S/23S nucleotide sequence of Fewa isolate was identical to that of strains 169, Maroc and ATCC 27556. Five nucleotide differences were observed in spiralin gene sequences of the two isolates, which has 99.30% similarity. Both the two spiralins comprised 241 amino acids and only three amino acids differences were observed between them, and their amino acids similarity was about 98.75%. Our findings indicated that both Fewa and Qua lubia isolates have high similarity in the nucleotide sequences of their 16S rDNA, 16S/23S rDN A intergenic spacer region and the nucleotides and amino acids of spiralin gene. However, they were not identical and could be differentiated by using restriction enzyme Bfal that digested at the recognition site CTAG within their spiralin gene sequence.
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