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ThesisItem Open Access Study of bacterial leaf spot of betel vine- biochemical changes and control(Department of Plant Pathology, College of Agriculture, Vellayani, 1986) Koshi, Abraham; KAU; James, MathewThe bacterial leaf spot is one of the most serious diseases of betel vine in Kerala. The bacterium is one of the most serious disease of betal vine. Confidering the seriouness of the disease , studies were undertaken on the different aspects of the disease and to find out a suitable control /management practice.ThesisItem Open Access Varietal screening of banana against anthracnose disease(Department of Plant Pathology, College of Horticulture, Vellanikkara, 1984) Srinagesh, K L; KAU; Jose, P CLaboratory and field studies of the varietal screening of banana against anthracnose disease were conducted at the college of Horticulture. Vellanikkara and at Banana Research Station, Kannara respectively during 1981-1983. In the field the infection started at the distal end of the banana fruit and in course of time the infected fruit became blackened, shriveled and mummified. After Harvest, the symptoms appeared as small brown spots which enlarged quickly and coalesced forming larger patches. The affected areas were covered with orange to salmon pink coloured conidial masses. The detailed morphological studies of the fungus proved that the anthraemose disease of banana is caused by colletrichum cloeosporioides cooko and massee, the imperfect stage of glomerella cinoulata spauld and shrenk. Twenty five varieties of banana fruit were screened in vitro at different stages of development against anthracnose disease. The varieties showed different degrees of susceptibility at various developmental stages of the fruit. The pooled analysis of the data showed that the variety nendra padaththi followed by palayankodan, jurmani kunthali, boodida bontha bathes, peyan, kanchikela, pisang mas and kapok were found to be highly resistant. The varieties Zanzibar, adakka kunnan, klue teparod, chinia, nendran, venneettu mannan, koduppilla kunnan, hybrid sawai, poocha kunnan, red banana and boodles altafort were found to be resistant to the disease. The variety robusta was found to be susceptible. The varieties njalipoovan, pisang lilin, dwarf Cavendish, matti and gros Michel were found to be highly susceptible. The major chemical constituents of banana fruit viz. reducing sugars, total sugars starch, crude fibre, crude protein and tannin at different developmental stages of twenty five varieties were analysed. The reducing sugars and total sugar were found to increase steadily from immediately after female phase to ripened stage in all the varieties. The starch and crude fibre contents, though increased steadily upto full maturity. Declined sharply at the ripening stage. The crude protein and tannin contents were maximum at immediately after female phase but steadily decreased and were minimum at ripening phase. There was a significant positive correlation between reducing sugars, total sugars and per cent disease intensity at three fourth maturity. High sugars were responsible for susceptibility to the disease. A significant negative correlation was obtained between crude protein and per cent disease intensity at half maturity. A significant negative correlation was also obtained between tannin and per cent disease intensity at one fourth and half maturity stages. High crude protein and high tannin contents were responsible for resistance to the disease.ThesisItem Open 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 MLaboratory, 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.ThesisItem Open Access Studies on the seed borne diseases of rice in Kuttanadu(Department of Plant Pathology, College of Agriculture, Vellayani, 1986) Jose Joseph; KAU; Susamma PhilipSeveral fungi were isolated from the seeds of twelve varieties/cultivars of rice collected from different localities of Kuttanadu, the major rice growing tract of Kerala. Fungi were encountered extrenally as well as internally. Among the externally seed borne fungi, Aspergillus flavus was the most common with its occurrence on nine varieties followed by Bipolaris oryzae and Curvuleria lunata. Other fungi included Rhizopus stolonifer, Chaetomium gracile, Syncephalestrum racemosum, Fusarium moniliforms, Trichoderma virde, Sarocladium oryzae. Aspergillus niger, Alternaria padwickii, Fusarium gramineazum, Piricularia oryzae, A. fumigatus, A. quadrilineatus, Nigrospora oryzae and Penicillium spp. Among the varieties Jaya was found to harbour the maximum fungal population. The germination percentage was not found to be affected due to seed inoculationwith the predominant fungi viz. A. flavus, A. padwickii, B. oryzae, C. lunata and S. oryzae.ThesisItem Open Access Epidemiology and control of sheath rot disease of rice(Department of Plant Pathology, College of Agriculture, Vellayani, 1986) Krishnakumaran Nair, B; KAU; Chandrasekharan Nair, MStudies on symptomatology, epidemiology and control aspects of sheath rot disease of rice caused by Serocladium oryzae Cams & Hawksworth (= Acrocylindrium oryzae Saw.) were done in detail. The disease initiated as purplish-brown oblong lesions on the sheath of the flag leaf. At maturity lesions enlarged in size with grey -white centres and often covered the entire flag leaf sheath. Panicle often did not emerge but choked inside the affected sheaf itself. Artificial inoculation studies showed that under sufficient humid conditions the pathogen took an average five to eight days for initiation and 15 to 20 days for the complete development of the disease in rice plants. The pathogen was isolated from four naturally infected rice varieties, collected from three different culture (isolates viz., S1, S2, S3, S4, S5, S6 & S7) were selected based mainly on symptomatological variations and their comperative morphological characters were studied in detail. No appreciable differences were noticed in the morphological characters between isolates.ThesisItem Open Access Strain variation in Rhizoctonia solani Kuhn [Thanatephorus cucumeris (Frank) Donk] causing sheath blight of rice(Department of Plant Pathology, College of Agriculture, Vellayani, 1986) Vijayan, M; KAU; Chandrasekharan Nair, NSymptoms of sheath blight disease usually develop towards the tillering stage of the rice crop. Discolouration initially appearing on the sheath at or above the water level develop into ellipsoidal lesions. The lesions are light greenish gray in colour with dark brown margin. As the disease progress the lesions coalesce and become oblong to irregular in shape. In severe condition the lesions encircle the culm and cause rotting of the sheath. The disease then spreads to the leaves and such plants are killed. Sclerotia and silvery threads of the fungal mycelium appear on the affected regions under high humid conition. The casual organism was Isolated and identified as Rhizoctonia solani Kuhn. The hyphae branched near the distal septus with a costriction at the branch base. Hyphae were multinucleate and in culture showed brown pigmentation. Nature sclerotia were subglobose with rough regular surface.ThesisItem Open Access Effect of application of plant protection chemicals on the survival of Rhizoctonia solani Kuhn(Department of Plant Pathology, College of Agriculture, Vellayani, 1986) Lulu Das; KAU; Chandrasekharan Nair, MIn Kerala, the incidence of sheath blight of rice is endemic causing great economic loss. The present investigation was undertaken to make a critical assessment of the efficacy of various palnt protection chemicals, viz., fungicides, insecticides and herbicides on the incidence and intensity of sheath blight of rice and on the survival of the pathogen. The organism was isolated from naturally infected rice fields and its pathogenicity proved. Studies on the viability of sclerotia revealed that they sclerotia remained viable upto 210 days in all the different types of soils namely sandy, clayey and loamy. The organism could survive on straw bits upto 180th ady only.ThesisItem Open 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, MMushrooms 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.ThesisItem Open Access Properties, host-range and control of cowpea mosaic virus(Department of Plant Pathology, College of Agriculture, Vellayani, 1987) Sreelakha, L; KAU; Balakrishnan, SStudies 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.
