Molecular identification,characterization and transmission of phytoplasmas associated with sesame phyllody in Turkey

Phyllody is a destructive disease of sesame in Turkey. The disease has been causing significant economic losses by stunting the plants and altering their floral parts into leafy structures with no capsule and hence no seeds in sesame fields of the country. This research was undertaken to examine symptomatology, etiology, taxonomy and transmission of two recently discovered phyllody phytoplasmas infecting sesame in Turkey. Direct and nested PCR amplifications of 16S rRNA gene with the phytoplasma-specific universal primers P1/P7 and R16F2n/R2, respectively were employed for identification of the phytoplasmas associated with sesame phyllody. Phytoplasma-specific PCR amplicons of 1.8 kb and 1.2 kb were amplified only from symptomatic sesame plants and insect vector samples. Sequencing of the PCR amplicons and computer simulated restriction fragment length polymorphism analysis allowed classification of the phytoplasmas with pigeon pea witches’-broom (16SrIX-C) and peanut witches’-broom (16SrII-D) groups. The sequence homology and phylogenetic analyses further confirmed this classification. Among the insects collected from the sesame fields, the leafhopper Orosius orientalis Matsumara (Syn: O. albicinctus Distant) was the only vector proven to transmit the sesame phyllody phytoplasmas from diseased to healthy sesame plants in transmission assays. The results demonstrated that the 16SrIX-C and 16SrII-D group phytoplasmas were the agent of sesame phyllody and O. orientalis was the vector insect of the disease in Turkey.