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Subject: Plant Pathology × Author: Ayisha, R × Thesis Type: M.Sc ×
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    ThesisItemOpen Access
    Characterisation of a tospovirus causing necrosis disease of cowpea (vigna unguiculata (L.) walp.)
    (Department of Plant Pathology, College of Agriculture, Vellayani, 2005) Ayisha, R; KAU; Umamaheswaran, K
    Studies were conducted on the tospo virus causing necrosis disease of cowpea [Vigna unguiculata (L.) Walp.] in Kerala. This investigation was conducted to characterize the virus. The characteristic symptoms appeared as chlorotic spots, veinal and bud necrosis, distortion and reduction in leaf size. Host range studies were done and the virus was found to have its host range in the members of the families Chenopodiaceae, Solanaceae, Leguminosae, Amaranthaceae and Malvaceae. The virus was mechanically transmitted through sap extracted in 0.01M phosphate buffer (pH 7.2) containing 2mercapto ethanol. The virus could be efficiently transmitted by the aphid vector, Aphis craccivora and Thrips palmi. The virus could be transmitted through graft but not through seeds. Thermal inactivation point was 50-55oC, dilution end point, 10-2-10-3 and longevity in vitro for 4 h at room temperature (28±2oC) and 8 h under refrigerated conditions (8oC). The virus causing necrosis was identified as tospo virus by ELISA and DIBA. Virus was related to WSMV, a tospo isolate. Biochemical changes indicated a decrease in chlorophyll content in virus inoculated leaves compared to healthy control. There was no significant difference observed in carbohydrates. Increase in protein content was observed in inoculated cowpea plants. The phenol content was found more in inoculated leaves compared to healthy control. The level decreased during later stages. Peroxidase, polyphenol oxidase and phenyl alanine ammonialyase showed a decreasing trend with age in both inoculated and healthy plants. But it was comparatively high in inoculated plants. Native polyacrylamide gel electrophoresis performed for PPO and peroxidase revealed that there was four isoforms of PPO for both inoulated and uninoculated control. Only quantitative change in one of the isoform was observed in PPO. One isoform in peroxidase was observed in inoculated plant but no isoform was observed in healthy. PAGE analysis of proteins with samples extracted from diseased and healthy plants showed the presence of three novel proteins in diseased sample. One of the proteins molecular weight, 28 kDa co-relates with the N-Protein of TSWV reported earlier.