Phytoplasmas are known as plant-pathogenic agents that cause great losses in economical plants. Phytoplasma diseases in potato, including potato whitches' broom and potato purple top, are documented worldwide, but there is no information confirming the importance of these diseases in Iran . In 2006-2007, symptoms typical of phytoplasma induced diseases were observed in sprouted seed tubers and potato plants in fields surveyed over an areas of Isfahan, Tehran, Kermanshah, Hamedan, Chaharmahal-O-Bakhtiari and East Azarbaijan provinces. The diseases are characterized by stunting, slight purple top, discoloration of new growth, leaf curl, swollen nodes, broken auxiliary buds and formation of aerial tubers similar to potato purple top disease symptoms. The potato sprouts emerged from generated tubers of these plants were spidle or hairy. Planting these symptomatic tubers in green house, promoted to produce potato purple top symptoms in generated plants, except one of them which showed witches,-broom symptoms with general stunting, yellowing and proliferation of auxiliary shoots. To detect phytoplasmas associated with infected plants, extracted DNA from sprouts of collected tubers or midrib of foliages was used as the template for nested PCR assay primed by phytoplasma universal primers P1/P7 and P1/Tint in the first round amplification followed by R16F2n/R16R2 and fU5/rU3 for nested reaction. Except for few DNA samples, no DNA amplification was observed when the P1/P7 and P1/Tint primers were used in first round PCR. However when direct PCR products were employed in nested PCR using R16F2n/R16R2 and fU5/rU3 primer pairs, fragments sized approximately 1239bp and 879bp DNA fragment were amplified respectively. Characteristic banding patterns obtained from restriction analysis of PCR products using Alu I, Eco RI, Cfo I, Kpn I, Hin dIII, Mse I, Rsa I and Taq I endonucleases from positive samples confirmed significant genetic differences among fragments of samples amplified in nested-PCR assay, indicating that divergent strains of phytoplasma might be involved in promoting whiches' broom and purple top symptoms in potato growing areas of Iran . The representatives of strains with different PCR-RFLP patterns were subjected to DNA sequencing. Nucleotide sequence comparison and alignment of a DNA-base segment of 16S rRNA gene sequences revealed that contained nucleotide sequences from representative isolates have high-level similarity (98-99%) to 16S rRNA phytoplasma sequences that were previously reported. Sequences analysis of 16S rRNA gen
