RESUMO
In symptomless plants of portulaca a potential new pospiviroid was characterized. Analysis by both double and return PAGE showed the presence of a circular RNA. RT-PCR and sequencing revealed a genome of 351 nt with properties characteristic of members of the genus Pospiviroid and with highest sequence identity (circa 80%) with iresine viroid 1 (IrVd-1). The circular RNA from portulaca was shown to replicate independently in its original host, thus showing that it is indeed a viroid. Based on its molecular characteristics, it should be considered a new species. However, since no biological differences have yet been found with its closest relative IrVd-1, the viroid from portulaca does not fulfil all criteria for species demarcation of the ICTV.
Assuntos
Doenças das Plantas/virologia , Portulaca/virologia , Viroides/isolamento & purificação , Sequência de Bases , Dados de Sequência Molecular , Conformação de Ácido Nucleico , Filogenia , RNA Viral/química , RNA Viral/genética , Viroides/classificação , Viroides/genética , Viroides/fisiologia , Latência ViralRESUMO
A southeastern European isolate of Alternanthera mosaic virus (AltMV-MU) of the genus Potexvirus (family Flexiviridae) was purified from the ornamental plant Portulaca grandiflora. The complete nucleotide sequence (6606 nucleotides) of AltMV-MU genomic RNA was defined. The AltMV-MU genome is different from those of all isolates described earlier and is most closely related to genomes of partly sequenced portulaca isolates AltMV-Po (America) and AltMV-It (Italy). Phylogenetic analysis supports the view that AltMV-MU belongs to a new "portulaca" genotype distinguishable from the "phlox" genotype.