Thumbnail Image

Theses

Browse

19872
Reset filters
Author: Sreelakha, L × End date: 1987 × Start date: 1984 × Type: Thesis × Thesis Type: M.Sc ×
Reset filters

Search Results

Now showing 1 - 2 of 2
  • Thumbnail Image
    ThesisItemOpen Access
    Properties, host-range and control of cowpea mosaic virus
    (Department of Plant Pathology, College of Agriculture, Vellayani, 1987) Sreelakha, L; KAU; Balakrishnan, S
    Studies were conducted on the cowpea mosaic virus disease commonly occurring in cowpea plants (Vigna unguiculata (L.) Walp) in Kerala The major symptoms caused by cowpea mosaic virus infection in cowpea plants were vein banding, inter- veinal chlorosis mosaic mottling and general stunting of the plants. Transmission studies showed that the virus could be transmitted through mechanical means, grafting, through seeds and by means of aphid vectors. The virus was found to be transmitted by the aphids, Aphis craccivora. Aphis gossvpii and Aphis malvae. Among the three species of aphids, Aphis craccivora was found to be the most efficient vector. The percentages of transmission obtained by A. craccivora, A. gossypii and A. malvae were 90,65 and 45 respectively. Studies on the physical properties of the virus revealed that the virus had a thermal inactivation pointbetween 50 and 55°C, dilution end point between 10“"* and —2 10 , longevity in vitro of 8 h at room temperature and24 h at 8°C. The minimum acquisition feeding and inoculation feeding period were found to be 30 s each. But the percentage of transmission was maximum when an acquisition feeding of 10 rain and inoculation feeding of 15 rain were given. Pre-acquisition fasting up to a period of 2 h increased the percentage of transmission, whereas the post-acquisition fasting decreased the efficiency of transmission. The vector was found to retain the virus for 1-2 h. Maximum percentage of transmission was obtained with 10 aphids and the symptoms appeared within 14 days after inoculation. Host-range studies revealed that the virus is restricted to the family Leguminosae and Chenopodiaceae. Varietal screening trial with ten different varieties of cowpea showed that all the ten varieties were susceptible to virus infection. C-152 was found to have the highest susceptibility of 100 per cent infection. C.G.104 showed some resistance with 13.33 per cent infection. In serological studies the cluster bean mosaic virus and sword bean mosaic virus were found to be related to cowpea mosaic virus. The antiserum titre and end point of virus in the present study were found to be between 1;1024 and 1:2048 and 1:512 and 1:1024 respectively. Studies on the effect of virus infection on growth of cowpea plants showed that there was significant reduction in height of the plant, number of pods produced and length of pods. Observations on natural incidence of cowpea mosaic virus indicated that cowpea mosaic virus is the major disease among the different virus diseases affecting t cowpea. Among the infected plants 57 per cent showed cowpea mosaic virus. The results of the experiments to find out the effect of leaf extract sprays on cowpea mosaic virus infection indicated that the disease could be effectively controlled by pre-inoculation sprayings with leaf extracts of Bougainvillea sp. and Eupatorium odoratum.
  • Thumbnail Image
    ThesisItemOpen Access
    Properties, hostrange and control of cowpea mosaic virus
    (Department of Plant Pathology, College of Agriculture, Vellayani, 1987) Sreelakha, L; Balakrishnan, S
    Studies were conducted on the cowpea mosaic virus disease commonly occurring in cowpea plants (Viena unguiculata (L.) Walp in Kerala. The major symptoms caused by cowpea mosaic virus infection in cowpea plants wars vein banding, inter- voinai cnlorosis, mosaic mottling and general stunting of the plants. Transmission studies showed that the virus could he transmitted through mechanical means, grafting,through seeds and by means of aphid vectors. The virus was found to be transmitted by the aphids, Aphis eracclvora. Aphis gossypil and Aphis rnalvae. Among the three species of aphids, Aphis craecivora was found to be the most efficient vector. The percentages of transmission obtained by A . craecivora, A. gossypii and A. malvae were 90,65 and 43 respectively.