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Subject: Plant Pathology × Author: KAU × End date: 1987 × Start date: 1987 ×
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    ThesisItemOpen Access
    Management of sheath blight disease of rice in relation to the population of the pathogen in soil
    (Department of Plant Pathology, College of Horticulture, Vellanikkara, 1987) Shaji, Alexander; KAU; Rajan, K M
    Laboratory, pot and field experiments were carried out to study the role of various physical, chemical and biological factors on the management of sheath blight disease of rice caused by Rhizoctonia solani Kuhn. (Thanatephorus Cucumerlis (Frank) Donk). Populations of total fungi, bacteria and actinomycetes in soil were enumerated at different stages of growth of the crop in order to assess their role in reducing the intensity and incidence of sheath blight disease. Results of the investigation revealed that the pathogen can be managed by deeper ploughing followed by submergence of the soil for a minimum period of two months. Amendments like glyricidia leaves, rice husk, lime and non edible oil cakes of marotti, neem and punna were useful in reducing the severity and spread of the disease. Fungicides like carbendazim and ediphenphos and the herbicide benthiocarb were also efficient in managing the disease. Rotation of rice with crops like tapioca, banana and brinjal was also useful. It was seen that amendments stimulated the population of saprophytes like Trichoderma viride in soil which are antagonistic to R. solani resulting in a subsequent reduction in population of the pathogen. In spite of the reduction in severity and spread of the disease, grain and straw yields were not enhanced by the treatments. More elaborate field trials are to be undertaken before landing on any ultimate conclusion regarding the use of these practices as tools for disease management.
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    ThesisItemOpen Access
    Monographic studies on edible species of pleurotus and standardisation of the techniques for large scale cultivation
    (Department of Plant Pathology, College of Agriculture, Vellayani, 1987) Suharban, M; KAU; Chandrasekharan Nair, M
    Mushrooms have long been recognized as a food because of their nutritive value and flavour and hence are grown on commercial scale on many parts of the world. In recent years cultivation of Pleurotus species are becoming popular in many of the tropical areas. No effort has been made in the past to collect, identify, describe and catalogue the Pleurotus mushroom flora of Kerala and standardise the techniques for their large scale cultivation. The present study was therefore initiated to achieve the above objectives. Collection, identification and description of the Pleurotus flora naturally occurred in and around the College of Agriculture and parts of Trivandrum district were carried out with the help of a data sheet. Twenty species of Pleurotus properly identified were further subjected to detailed study. A key was constituted to enable easy identification of gill the twenty described species. Out of the twenty species described, eight species are new records for India. Among the common cultivable species of Pleurotus. P .sajor-caju was found to be the most suitable mushrooms for the warm humid climatic condition of Kerala. The optimum temperature for maximum growth of this mushroom was found to be between 15 to 50 *C. Comparative efficacy of various containers and substrates used for spawn production revealed that Maize and empty wine bottle were the best substrate and container respectively for spawn production. Trials on cultivation of P. sajor-caiu on logs of common trees revealed Mango tree log to be the best in getting higher yield. Polythene bag was found to be the best container in supporting maximum sporocarp formation. Straw of local varieties of rice were better than high yielding varieties of rice in supporting sporocarp, formation. Comparative efficacy of straw made into bits and small twists with six species of Pleurotus revealed higher yield of 775 g per kg of substrate with spawn of Pleurotus- sajor-caju establishing its superiority for cultivation in Kerala. Cultivation of P .saior-caju in different seasons of the year revealed that this mushroom can be successfully cultivated in Kerala all through the year on paddy straw.
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    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.
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    ThesisItemOpen Access
    Effect of inoculation of vesicular-arbuscular mycorrhiza on nodulation and phosphorus uptake in cowpea
    (Department of Plant Pathology, College of Agriculture, Vellayani, 1987) Meena Kumari, K S; KAU; Sasikumar Nair
    A study on the effect of inoculation of vesicular- arbuscular mycorrhiza and Rhizobium on nodulatlon, phosphorus uptake and yield in coupe a was conducted at College of Agriculture, Vellayani, Trivandrum during 1983-85. Three separate pot culture experiments were conducted during this Investigation; Initially, ten cowpea varieties were screened for the natural incidence of YA-mycorrhiza., There were significant differences between varieties in their mean mycorrhizal index; The infection was maximum in C-152 which had an average index of 1.19. This was significantly higher than that of varieties such as CG-11, HG-22, PTB-1, RC-25, S-488, IT-16 and V-38; The application of rock phosphate had a significant effect in enhancing the mycorrhizal infection in all varieties except in S-488. The cowpea variety which had the maximum mycorrhizal index under natural conditions m s further used to study the effect of age of host plant on mycorrhizal infection. This ms significantly higher on 45th day. The application of rock phosphate at the rate of 30 kg P2 O5/ha had a uniform significant effect in enhancing the mycorrhizal infection at different stages of plant growth. In the last part, a detailed study on the combined effect of VA-mycorrhiza and Rhizobium inoculation on nodulation, phosphorus uptake and yield in cowpea was conducted. Observations were taken at two stages of plant growth, on. 45th day and at the time of harvest. A uniform treatment effect on various plant characters studied was observed only at the time of harvest. The number of nodules formed per plant and their fresh (and dry weights were significantly higher in the treatment combination consisting of the standard culture of VA-mycorrhiza, Rhisobium inoculation and the application of rock phosphate at the rate of 30 kg P205/ha. The fresh and dry weights of plants and the mean mycorrhizal index were also maximum in this (MSR+RP) treatment.
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    ThesisItemOpen Access
    Post harvest deterioration of fruits by microbes and their control
    (Department of Plant Pathology, College of Agriculture, Vellayani, 1987) Anita Cherian, K; KAU; Susamma Philip
    Several fungi and bacteria was isolated from decayed fruits like banana, mango, pineapple and orange collected from the local markets of Trivandrum city over a period of six months, Among these Botryodiplodia theobromas was the most common fungus with its occurrence on all fruits. Other pathogenic fungi isolated from each fruit