| Abstrakt: |
Phyllody associated with the presence of ‘CandidatusPhytoplasma’ strains is the most important disease, severely affecting sesame plants, either partially or completely. Seven species of sesame, namely Sesamum alatum, S. indicum, S. malabaricum, S. mulayanum, S. radiatum, S. laciniatumand S. prostratumwere studied for their resistance or susceptibility to phyllody, symptomatology and identification of the phytoplasma involved in symptom development. Symptoms viz.,phyllody and flower virescence were recorded in all the seven species of Sesamumwith varying degrees of susceptibility. Some sesame species exhibited yellowing of leaves, stunted growth, little leaves, proliferation of axillary shoots, witches’-broom, and splitting of capsules. The lowest incidence of phyllody was found in S. alatum(0–6%), followed by S. laciniatum(11–17%) and S. prostratum(16–27%). The incidence of phyllody in S. indicum, S. malabaricum, S. mulayanumand S. radiatumwas between 44–68%. In the present investigation, two phytoplasma strains, 16SrI-B (‘CandidatusPhytoplasma asteris’) and 16SrII-D (‘CandidatusPhytoplasma australasia’) were identified in phyllody affected Sesamumspecies. The perennial species S. laciniatumand S. prostratum, found only in India, are at risk of extinction due to phyllody and pose a serious threat as inoculum source for the spread of the disease. In the future, focus on genome sequencing of ‘CandidatusPhytoplasma’ strains associated with phyllody in Sesamumspecies and identification of the insect vectors involved in phytoplasma transmission are essential to clarify the phytoplasma strain identity and understand the host–pathogen-vector relationship. |
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