Detection and molecular characterization of a phytoplasma associated with Cucumber (Cucumis sativus) and its first report from India

Cucumber (Cucumis sativus) plants exhibiting typical phyllody symptoms were collected from farmers field of Chintamani, Chickballapur districts of Karnataka (India). Disease incidence of phyllody was 2-3%. The etiology of the cucumber phyllody phytoplasma (CuPP) was confirmed by amplifying 16S rRNA gene from symptomatic plants using PCR followed by nested PCR using universal primers pairs P1/P7 and R16F2n/R16R2. After general detection the non-ribosomal SecY and rp (ribosomal protein) genes was amplified using specific primers. The PCR amplified products 16SrRNA (1.2 kb), SecY (1.6 kb) rp gene (1.2 kb) was cloned and sequenced. Sequence and phylogenetic analyses of 16S rRNA, secY and rp genes revealed that the detected phytoplasma is a member of the 16SrI group (Candidatus Phytoplasma asteris). Further on the basis of computer-simulated RFLP (= in silico RFLP) analysis of amplified F2n/R2 region of 16S rRNA gene indicates that, the detected phytoplasma was belongs to the subgroup X (16SrII-X). This is the first report on phytoplasma associated with phyllody disease of cucumber in India.