RESUMEN

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'.

Asunto(s)

Catharanthus/microbiología , Filogenia , Phytoplasma/clasificación , Enfermedades de las Plantas/microbiología , Técnicas de Tipificación Bacteriana , ADN Bacteriano/genética , México , Phytoplasma/genética , Phytoplasma/aislamiento & purificación , Polimorfismo de Longitud del Fragmento de Restricción , ARN Ribosómico 16S/genética , Análisis de Secuencia de ADN

RESUMEN

Symptoms of abnormal proliferation of shoots resulting in formation of witches'-broom growths were observed on diseased plants of passion fruit (Passiflora edulis f. flavicarpa Deg.) in Brazil. RFLP analysis of 16S rRNA gene sequences amplified in PCRs containing template DNAs extracted from diseased plants collected in Bonito (Pernambuco) and Viçosa (Minas Gerais) Brazil, indicated that such symptoms were associated with infections by two mutually distinct phytoplasmas. One phytoplasma, PassWB-Br4 from Bonito, represents a new subgroup, 16SrIII-V, in the X-disease phytoplasma group ('Candidatus Phytoplasma pruni'-related strains). The second phytoplasma, PassWB-Br3 from Viçosa, represents a previously undescribed subgroup in group 16SrVI. Phylogenetic analyses of 16S rRNA gene sequences were consistent with the hypothesis that strain PassWB-Br3 is distinct from previously described 'Ca. Phytoplasma' species. Nucleotide sequence alignments revealed that strain PassWB-Br3 shared less than 97.5 % 16S rRNA gene sequence similarity with previously described 'Ca. Phytoplasma' species. The unique properties of its DNA, in addition to natural host and geographical occurrence, support the recognition of strain PassWB-Br3 as a representative of a novel taxon, 'Candidatus Phytoplasma sudamericanum'.

Asunto(s)

Passiflora/microbiología , Filogenia , Phytoplasma/clasificación , Enfermedades de las Plantas/microbiología , Brasil , Datos de Secuencia Molecular , Phytoplasma/genética , Phytoplasma/aislamiento & purificación , Reacción en Cadena de la Polimerasa , Polimorfismo de Longitud del Fragmento de Restricción , ARN Ribosómico 16S/genética , Alineación de Secuencia

RESUMEN

A previously undescribed phytoplasma, Erigeron witches'-broom phytoplasma, was detected in diseased plants of Erigeron sp. and Catharanthus roseus exhibiting symptoms of witches'-broom and chlorosis in the state of São Paulo, Brazil. On the basis of restriction fragment length polymorphism (RFLP) analysis of 16S rDNA amplified in the polymerase chain reaction (PCR), Erigeron witches'-broom phytoplasma was classified in group 16SrVII (ash yellows phytoplasma group), new subgroup VII-B. Phylogenetic analysis of 16S rDNA sequences indicated that this phytoplasma represents a new lineage that is distinct from that of described strains of ash yellows phytoplasma. Erigeron witches'-broom phytoplasma is the first member of the ash yellows phytoplasma group to be recorded in Brazil.

RESUMEN

Corn stunt disease is a major limiting factor in production of corn (Zea mays) in the Americas. To develop a polymerase chain reaction (PCR) assay specific for detection of the causal agent, Spiroplasma kunkelii, PCR primers were designed on the basis of unique regions of the nucleotide sequence of the S. kunkelii spiralin gene. DNA was amplified in PCRs containing template DNAs derived from laboratory strains of S. kunkelii and from naturally diseased corn plants collected in the field. No DNA amplification was observed in PCRs containing template DNAs derived from other Spiroplasma species tested or from healthy corn or corn infected by maize bushy stunt phytoplasma. The availability of a sensitive and specific PCR for detection and identification of S. kunkelii should facilitate studies of the ecology of this pathogen, as well as its influence in the incidence, spread, and severity of corn stunting diseases.