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Subject: Plant Pathology × Author: Abhilash Dinkar × End date: 2012 × Type: Thesis × Thesis Type: M.Sc ×
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    ThesisItemOpen Access
    Viral diseases of Vanilla(Vanilla planifolia Andrews) in Kerala
    (Department of Plant Pathology, College of Agriculture, Vellayani, 2006) Abhilash Dinkar; KAU; Joseph, P J
    Preliminary survey conducted in Kottayam and Idukki districts of Kerala indicated the incidence of three virus diseases in vanilla and were categorized as those producing a) Symptom Type No.1 b) Symptom Type No.2 and c) Symptom Type No.3. The most widely occurring virus disease was the one which produced Symptom Type No.1, the characteristic symptoms of which were mosaic pattern on leaves up on which necrotic spots developed later with leaf crinkling, distortion, and leaf size reduction. The virus is named as Vanilla mosaic virus disease (VMVD). The disease was prevalent in the two districts surveyed. The mean per cent disease incidence varied from 6.683 to 8.205 during summer season. The mean disease index varied from 2.553 to 2.976 during summer season .The virus was not sap transmissible to vanilla test plants but was easily transmissible to Chenopodium amaranticolor, exhibiting chlorotic local lesions in which highest per cent transmission was obtained using 0.1M sodium phosphate buffer (pH7.2). The disease was not transmitted by insects such as Aphis gossypii, A. craccivora and Bemisia tabaci. Hundred per cent transmission was obtained when infected cuttings were used as planting material. The virus was found to be transmitted to vanilla test plants by wedge and approach grafting and budding even though perfect graft and bud union did not establish. The virus has a dilution end point between10-4 and10-5, thermal inactivation point between 60and 65oC and longevity in vitro at room temperature between 24 and 48 hours and under refrigerated conditions between 48 and 72 hours. The virus could be transmitted only to Nicotiana glutinosa systemically and to C.amaranticolor with local lesions. Drastic reduction in total chlorophyll, chlorophyll a, chlorophyll b and total carbohydrate were observed in virus infected plant samples while total soluble protein and phenol content were greatly enhanced. Peroxidase, polyphenol oxidase and phenylalanine ammonia lyase activities were found to be increased in response to virus infection. SDS PAGE analysis revealed the presence of an additional major polypeptide band of 37 KDa in infected samples in addition to the identical bands. The virus was partially purified and antiserum was successfully produced with a titre between 1:500 and 1:1000. A rapid method of diagnosis of vanilla mosaic virus disease was developed employing microprecipitin and DAC- ELISA tests.