Abstract
Phytoplasma diseases are threat to sesame and its wild relatives, but information on their occurrence in exotic
Sesamum
species is limited. During field evaluation,
Sesamum angolense
,
S. angustifolium
, and
S. latifolium
exhibited characteristic phyllody and witches' broom symptoms, including virescence, leafy floral organs, polysepalous calyx, polypetalous corolla, flattened stamens, shortened internodes, excessive shoot proliferation, and leaf twisting and curling. Molecular detection using universal phytoplasma primers P1/P7 and
tuf
gene-specific primers fTufAy/rTufAy amplified products of approximately 1.8 kb and 940 bp, respectively, from symptomatic plants. Sequence analysis of the 16S rRNA and
tuf
genes revealed 99–100% nucleotide identity with members of the
'Candidatus
Phytoplasma asteris
'
group. Phylogenetic reconstruction based on both loci consistently assigned the isolates to the 16SrI-B subgroup of
'Ca.
Phytoplasma asteris'. To the best of our knowledge, this is the first report of phytoplasma infection in
S. angolense
,
S. angustifolium
, and
S. latifolium
, characterized at the strain level using both 16S rRNA and
tuf
gene sequences. The findings expand the known host range of 16SrI-B phytoplasmas and demonstrate that these wild
Sesamum
species, which are valuable components of the tertiary gene pool of cultivated sesame, can serve as natural reservoirs of phytoplasma inoculum.