Division of Crop Protection, Indian Institute of Spices Research, Marikunnu, Calicut-673012, Kerala.
Abstracts of the papers presented at the 16th Annual Convention and International Symposium of Indian Virological Society on “Management of Vector-Borne Viruses” at International Crops Research Institute for the Semi-Arid Tropics (ICRISAT), Patancheru-502324, Hyderabad, India, February 7–10, 2006.
Vanilla (Vanilla planifolia Andrews) is an expensive spice cultivated for its highly priced beans. In India, viral diseases have become serious due to the recent intensive cultivation. Survey of vanilla plantations of Kerala and Karnataka showed occurrence of mosaic, leaf curl, stunting and necrosis diseases with an average incidence ranging from 0–5%. Many of the affected vines are at their pre-bearing period and incidence of the disease is expected to increase as the crop is propagated by vegetative means. Electron microscopy of leaf dip preparations of diseased plants revealed the presence of three kinds of flexuous particles resembling Potexvirus, Potyvirus and Closterovirus and an isometric particle. Of these the isometric virus was identified to be a strain of Cucumber mosaic virus (CMV) belonging to subgroup IB on the basis of biological, serological and coat protein (CP) nucleotide sequence properties. Sequence analyses with other CMV isolates revealed the greatest identity with black pepper isolate of CMV (99%) and the phylogram clearly showed that CMV infecting vanilla belongs to subgroup IB. The Potexvirus infecting vanilla was identified as strain of Cymbidium mosaic virus (CymMV) based on coat protein nucleotide sequence relationships. An identity of 92.3 to 97.3% was seen with different CymMV isolates from India while with available partial CP sequences of CymMV isolates infecting vanilla from French Polynesia and Reunion Island, identity ranged from 98.2 to 99.4%. The Potyvirus infecting vanilla has been isolated, purified and further characterization is underway. As vanilla is clonally propagated through stem cuttings, ELISA and RT-PCR based methods were standardized for the reliable detection of viruses in planting materials to check spread of the virus.
