First report of ‘Candidatus Phytoplasma asteris’ strains associated with phyllody of Rudbeckia in Türkiye

During field surveys conducted in 2024, Rudbeckia species plants (Asteraceae) exhibiting symptoms of phyllody, virescence, axillary shoot proliferation, and stunting were observed in public gardens in Istanbul, Türkiye. To investigate possible phytoplasma presence, symptomatic plants were analyzed by polymerase chain reaction (PCR) using universal primers targeting ribosomal 16S rRNA gene. All symptomatic samples tested positive and PCR with primer pair P1/P7 followed by nested PCR with R16F2n/R16R2, consistently yielded amplicons of the expected size (1.25 kb). Sanger sequencing of the 16S rRNA gene and BLASTn analysis against the NCBI database revealed 99.30–99.44% sequence identity with ‘Candidatus Phytoplasma asteris’ and other members of the aster yellows group (16SrI). Phylogenetic analysis further confirmed that the sequences clustered within phytoplasma strains enclosed in subgroup 16SrI-B. This study provides the first evidence of phytoplasma infection in Rudbeckia species in Türkiye and expands the documented host range of phytoplasmas in this region of Türkiye.