'Bunchy top symptom' of papaya in Cuba: new insights

Papaya is an important export crop in Cuba. A disease named Bunchy top symptom (BTS) was first observed in 2003 from Villa Clara province, but is now widespread throughout the country. A nested PCR assay with 16S rDNA phytoplasma primers P1/P7 and R16F2n/R2 was used to index more than 2200 papaya plants, weeds and insect samples collected between November 2005 and June 2006. RFLP patterns for all amplicons were identical with HaeIII, RsaI and AluI enzymes. No rickettsia-like bacteria were found in any of the samples. Phytoplasma rDNA was amplified from 1449 (89.7%) papaya plants with BTS symptoms. Phytoplasma rDNA was also detected in 331 apparently healthy papayas, and other plant species: Anoda acerifolia (57), Euphorbia heterophylla (73), Malvastrum coromandelianum (41) and Rynchosia minima (37) and 60/75 batches of Empoasca papayae. Sequences from the phytoplasma in papaya (DQ868531), A. acerifolia (DQ286950); E. heterophylla (DQ286951); M. coromandelianum (DQ286952); R. minima (DQ868533) and the leafhopper E. papayae (DQ868532) all showed 99% similarity to the phytoplasma associated with polygala phyllody, PPhy, (AY787140) belonging to the 16SrII group, ‘Candidatus Phytoplasma aurantifolia’. The discovery of the BTS phytoplasma in weed species and a putative vector Empoasca papayae suggests, that these plants and the leafhopper may have role in the spread of this disease.