RESUMO
The present study was carried out to determine if group 16SrIV phytoplasmas, causing lethal yellowing (LY) disease, are present in Haplaxius crudus Van Duzee (Hemiptera: Cixiidae) insects associated with palms in Yucatán, Mexico. Haplaxius crudus feral insects were captured from palm foliage at two locations (Chicxulub Puerto and CICY, Mérida, where LY-type diseases are active) and evaluated individually for the presence of phytoplasma DNA by a group 16SrIV-specific nested PCR assay. The results showed positive detection in H. crudus insects in a proportion of 2.7% (of the total 2726 analyzed) during a 3-year period of study. The percentage of detection was different for each site, 5.9% positive of 799 insects from Mérida and 1.7% of 1927 from Chicxulub Puerto. Positive detections were also obtained in extracts from 5.3 to 1.2% of males and females, respectively. Sequencing and in silico RFLP and phylogenetic analyses of PCR-amplified rDNA products indicated that H. crudus insects from Chicxulub Puerto harbored phytoplasma strains of subgroups 16SrIV-A or 16SrIV-D, whereas in insects from Mérida the strains found were 16SrIV-A, 16SrIV-D or 16SrIV-E. The diversity of subgroup strains detected in H. crudus coincided with strains previously identified in palms showing LY-type disease syndromes in Yucatán thereby implicating H. crudus as a candidate vector of 16SrIV phytoplasmas in this region of Mexico.
RESUMO
Mexican periwinkle virescence (MPV) phytoplasma was originally discovered in diseased plants of Madagascar periwinkle (Catharanthus roseus) in Yucatán, Mexico. On the basis of results from RFLP analysis of PCR-amplified 16S rRNA gene sequences, strain MPV was previously classified as the first known member of phytoplasma group 16SrXIII, and a new subgroup (16SrXIII-A) was established to accommodate MPV phytoplasma. Phylogenetic analysis of 16S rRNA gene sequences indicated that strain MPV represents a lineage distinct from previously described 'CandidatusPhytoplasma' species. Nucleotide sequence alignments revealed that strain MPV shared less than 97.5 % 16S rRNA gene sequence similarity with all previously described 'Ca.Phytoplasma' species. Based on unique properties of the DNA, we propose recognition of Mexican periwinkle virescence phytoplasma strain MPV as representative of a novel taxon, 'CandidatusPhytoplasma hispanicum'.