A new phytoplasma associated with witches\u2019 -broom of Cassia italica in Oman.

In several Oman locations plants of Cassia italica exhibit witches\u2019 broom symptoms. Samples were collected from four locations, and examined for phytoplasma presence. PCR amplification using ribosomal phytoplasma primers followed by RFLP analyses indicates that the phytoplasmas present in these samples were undistinguishable from each other, but differed from those reported in the literature. RFLP and phylogenetic analysis of 16S rRNA gene plus spacer sequence confirmed that the closest phytoplasma relatives were members of the pigeon pea witches\u2019 broom phytoplasma ribosomal group (16SrIX), sharing a 93-97% sequence similarity. Nested PCR experiments using primers amplifying the gene coding for ribosomal protein S3 provided amplification from phytoplasmas detected in C. italica, after sequencing 600 bp in this gene the higher homology showed was 78% with phytoplasmas related to \u2018Candidatus Phytoplasma phoenicium\u2019 and 77% with phytoplasmas belonging to ribosomal group 16SrIX

\u2018Candidatus Phytoplasma omanense\u2019, a phytoplasma associated with witches\u2019 broom of Cassia italica (Mill.) Lam. in Oman.

Samples from plants of Cassia italica exhibiting typical witches\u2019-broom symptoms (Cassia witches\u2019-broom; CWB) were examined for the presence of plant pathogenic phytoplasmas by PCR amplification using universal phytoplasma primers. All affected plants yielded positive results. RFLP analyses of rRNA gene products indicated that the phytoplasmas detected were different from those described previously. Phylogenetic analysis of 16S rRNA gene sequences confirmed that CWB represents a distinct lineage and shares a common ancestor with \u2018Candidatus Phytoplasma phoenicium\u2019. Molecular comparison revealed that the 16S rRNA gene sequences of the four CWB strains (IM-1, IM-2, IM-3 and IM-4) identified in symptomatic C. italica samples were nearly identical (99.6\u2013100% similarity). The closest relatives were members of the pigeon pea witches\u2019-broom phytoplasma ribosomal group (16SrIX; 95\u201397% sequence similarity). On the basis of unique 16S rRNA gene sequences and biological properties, the phytoplasma associated with witches\u2019-broom of C. italica in Oman represents a coherent but discrete novel phytoplasma, \u2018Candidatus Phytoplasma omanense\u2019, with GenBank/DDBJ/EMBL accession number EF666051 representing the reference strain