Association of the 16SrII-D phytoplasma with African Marigold (Tagetes erecta) Phyllody in Oman

The African marigold (Tagetes erecta L.) is an ornamental, herbaceous plant commonly found in Oman. In 2019, African marigold plants showing phyllody and virescence symptoms, which are typical symptoms of phytoplasmas disease, were found in at Sultan Qaboos University in Oman. Transmission electron microscopy of marigold leaf midrib from phyllody disease plants showed the presence of numerous phytoplasma bodies in the sieve tube of all of the symptomatic samples. DNA was extracted from asymptomatic and symptomatic marigold plant samples, followed by PCR of the 16S ribosomal RNA (rRNA) and imp genes. The PCR assays showed that the symptomatic plants are positive for phytoplasma. The DNA sequence analysis and phylogenetic trees showed that the 16S rDNA and imp gene sequences from all marigold phyllody strains shared 100% sequence identity to 16SrII-D subgroup sequences in the GenBank. This is the first report of a phytoplasma of the 16SrII-D subgroup associated with the African marigold (T. erecta) worldwide.