ABSTRACT

Phytoplasmas are a diverse group of cell wall-less, pleomorphic fastidious prokaryotes linked to diseases in over a thousand species globally. A systematic survey was conducted across eight specific locations within Canara circle under the Western-Ghat part of Karnataka in collaboration with the Karnataka Forest Department. The witches’ broom affected Trichilia connaroides showed symptoms like chlorotic leaves, excessive shoot proliferation, reduced leaf size and bushy appearance of branches in two locations [Bhairumbe (Lat- 14.70296, Long- 74.82148) and Potoli cross (Lat- 15.18635, Lon- 74.55529). Rosette infected Ficus amplecissima showed apical rosette formation, small leaves, severe internodal shortening, pendulous twigs formations with upright growth in one location [Bhagwathi (Lat- 15.1541, Long- 74.7557)]. Ziziphus oenoplia exhibited little leaf symptoms which includes stunted branches, shortened internodes, narrow leaves and mild chlorosis in two locations [Bommanali (Lat- 14.68545, Long- 74.8284) and Bhagwathi (Lat- 15.16996, Long- 74.72024)]. While witches’ broom affected Xylia xylocarpa showed crowded branches, shortened internodes and reduced leaf size in three locations [Ganeshgudi (Lat- 14.98317, Long- 74.57772), (Lat-14.98302, Long-74.5767), (Lat- 14.98302, Long-74.5767)].
In disease calendar of Trichilia connaroides, disease progression was observed slow and influenced by climatic and seasonal factors. Electron microscopy of ultrathin sections from infected T. connaroides, Z. oenoplia, Toona ciliata and Dendrocalamus strictus revealed pleomorphic bodies within the phloem tissues. PCR using phytoplasma specific primers (P1/P7 and R162n F/R162n R) consistently amplified 1.8 kb and 1.2 kb fragments from symptomatic T. connaroides, T. ciliata, D. strictus and Z. oenoplia and 537 bp DNA fragments from F. amplecissima. Phylogenetic analysis revealed that the phytoplasma strain causing witches’ broom disease in T. ciliata and T. connaroides belongs to ‘Ca. P. asteris’ (16Sr I group), while Z. oenoplia is closely related to ‘Ca. Phytoplasma balanitae’ (16SrV) group.