A subgroup 16SrIII-X phytoplasma is associated with small leaf proliferation in goldenrod plants

Solidago microglossa (goldenrod) is a species with medicinal properties, generating products of estimable economic value, which are commercialized as medicines and cosmetics. Plants of S. microglossa exhibiting intense proliferation of small leaves, producing a compact canopy, were found sparsely in a field. Since these symptoms are indicative of infection by phytoplasmas, a survey was performed in order to understand the etiological cause of observed symptoms. The total DNA extracted from the tested plants was used in nested PCR primed by P1/16S-SR followed by R16F2n/R16R2. Leaf veins were appropriately prepared for visualization in transmission electron microscopy. The presence of phytoplasma was revealed in symptomatic samples by amplification of genomic fragments of 1.25 Kb. In agreement, phytoplasma cells were observed in the phloem vessels of these plants. Nucleotide sequences from the phytoplasma were indistinguishable among themselves and shared 99.7% identity with sequences of phytoplasmas belonging to the 16SrIII group. Computer-simulated RFLP and phylogenetic analysis classified the S. microglossa phytoplasma as member of the 16SrIII-X subgroup. In addition, the present study revealed S. microglossa as an additional host species for this phytoplasma.