1. KAUTIR (Kerala Agricultural University Theses Information and Retrieval)

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    Properties, host-range 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 (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.
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    Yellow vein mosaic disease of pumpkin in Kerala
    (Department of Plant Pathology, College of Agriculture, Vellayani, 1984) Jayasree, P K; Balakrishnan, S
    Yellow vein mosaic disease of pumpkin ( Cucurbita moschata Dutch. ex Poir) caused by a virus, was investigated which was prevalent in Vellayanl and nearby localities. The symptoms appeared as faint yellowing of finer veins which later on develop into characteristic vein yellowing. In advanced stages of infection, chlorotic areas were seen on the leaf lamina along with vein yellowing symptoms. The size of the leaves was reduced markedly.The growth of infected plants was severely retarded. The infected plants produced less female flowers and when Infected at a later stage produced undersized fruits. Histopathological studies showed a reduction in thickness of the chlorotic portions of the infected leaves and the palisade cells were shortened and loosely packed. The mesophyll cells contained only few chloroplasts. The virus was not sap transnissible. But it could be transnitted through grafting* The virus was hot found to be transmitted through seeds.
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    Studies on leaf curl disease of sesamum
    (Department of Plant Pathology, College of Agriculture, Vellayani, 1984) Jayasree, M; Balakrishnan, S
    Leaf curl disease of sesamum, its symptomatology, mode of transmission, vector-virus relationships, the pattern of spread under field conditions and the extent of loss caused by the disease were investigated. Major symptoms of the disease were abaxial curling of the leaves, thickening of the veins on the under surface of the leaves, leathery appearance of the leaves and reduction in the size of leaf lamina. The plants remained stunted and produced few flowers and pods when infection occurred during the early stages of the plant growth. When infection occurred during later stages there was production of flowers and pods hut to a limited extent. This particular virus could he transmitted by wedge and side grafting and by the whitefly Bemisia tabaci Genn. The minimum, acquisition feeding period was found to be 10 min and the minimum inoculation feeding period was 20 min. The vector required an incubation period of 28 h to become viruliferous. Even a single whitefly was found to be capable of transmitting the virus. Once the vector acquired the virus it would retain it till its death. Negative results were obtained in the case of sap and seed transmission showing that this particular virus was not sap and seed transmissible.
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    Transmission, physical properties and host range of brinjal mosaic virus
    (Department of Plant Pathology, College of Agriculture, Vellayani, 1996) Surendran, M; Rajagopalan, B
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    Properties, Hostrange and control of cowpea mosaic virus
    (Department of Plant Pathology, College of Agriculture, Vellayani, 1987) Sreelakha, L
    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.