'Candidatus Phytoplasma graminis' and 'Candidatus Phytoplasma caricae', two novel phytoplasmas associated with diseases of sugarcane, weeds and papaya in Cuba.

ABSTRACT

During 2003, surveys of sugarcane yellow leaf disease and papaya bunchy top-like disease were carried out on plantations in Havana province, Cuba, to determine the roles of weeds and Auchenorrhyncha insects in the epidemiology of these diseases. More than 250 plant and insect samples were collected and indexed by using a nested PCR for phytoplasma 16S rDNA with the generic primer pairs P1/P7 and R16F2n/R16R2. The PCR products were further characterized by restriction fragment length polymorphism using HaeIII, AluI, Sau3AI, Tru9I, HhaI, HpaII and TaqI endonucleases, giving patterns that distinguished them from those of the other reference phytoplasmas analysed. Phylogenetic analysis of 16S rRNA gene sequences identified the phytoplasmas present in sugarcane (Saccharum officinarum L.), Cynodon dactylon L., Conyza canadensis L. Cronq., Sorghum halepense L. Pers., Macroptilium lathyroides L. Urb., Saccharosydne saccharivora (Westwood) and Cedusa spp., and those in papaya (Carica papaya L.) and Empoasca papayae, as two novel provisional phytoplasma species. We propose that these phytoplasmas should be given Candidatus status, as 'Candidatus Phytoplasma graminis' and 'Candidatus Phytoplasma caricae', respectively.