First report of a 16SrII (Candidatus Phytoplasma aurantifolia) group phytoplasma associated with a bunchy-top disease of papaya in Cuba

Phytoplasmas of the 16SrII and 16SrXII groups were first reported to cause mosaic, yellow crinkle and dieback of papaya in Australia (Gibb et al., 1996). In Havana province (western) Cuba, papaya bunchy-top like-disease (PBT-like) is associated with Candidatus Phytoplasma caricae belonging to a new 16SrXVII group (Arocha et al., 2005). During September-October/2005, typical PBT-like symptoms were seen extensively in papaya plantations of Guantánamo, Santiago de Cuba, Granma, Camagüey and Holguín provinces of eastern Cuba. Leaf samples from 177 plants showing PBT-like symptoms, 53 apparently healthy (symptomless) and 67 Empoasca spp. (delphacid leafhopper) were collected and tested for the presence of phytoplasmas using universal phytoplasma rDNA primer pairs P1/P7 and R16F2n/R16R2. A 1250 bp fragment was amplified from each of 171 plants with symptoms, 63 Empoasca spp., but none of the symptomless plants. There was no sign of the new Candidatus Phytoplasma caricae (16SrXVII), previously identified in Havana, with RFLP analysis with restriction endonucleases HaeIII, RsaI and AluI giving typical patterns for 16SrII group phytoplasmas for all plant and insect samples. Two randomly selected P1/P7 PCR products from the 171 plants with symptoms and two from the 63 insect samples were directly sequenced. BLAST analysis of rDNA sequences showed their highest similarity (99%) to that of Polygalla phyllody phytoplasma (GenBank accession No. AY787140); a member of the 16SrII group (Candidatus Phytoplasma aurantifolia). Sequences were deposited in GenBank (Accession No. DQ286948, papaya and DQ286949, Empoasca spp.). This is the first record of a 16SrII phytoplasma in papaya and in a putative Empoasca spp. vector from Cuba, and indicates this is the most likely phytoplasma as the causal agent of PBT-like disease.