PG Thesis
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Item Studies on the leaf blight disease of clove caused by Cylindrocladium sp.(Department of Plant Pathology, College of Agriculture, Vellayani, 1980) Sulochana, K K; Chandrasekharan Nair, NLeaf blight disease of clove caused by Cylindrocladium cuinqueseptatum Boedijn et Roitsma was investigated. The fungus infected clove leaves at all stages of maturity, but the seedlings were found to be more susceptible to the disease than mature plants. Injury of the host tissue was found to be a pre-requisite for successful infection by the fungus. The organism infected a wide variety of plants including some of the weed plants on artificial inoculation. Good growth and sporulation of the fungus was obtained on potato dextrose agar followed by Coon’s agar and Czapek’s agar. In liquid media, maximum dry weight of the mycelium was obtained on potato media, maximum dry weight of the mycelium was obtained on potato dextrose broth, followed by Czapeks’ broth. Maximum growth of the fungus was obtained on medium amended with gingelly oil followed by coconut and clove oils. In liquid media, maximum dry weight of the mycelium was obtained in the medium amended with gingelly oil followed by coconut clove oils. Optimum pH range for the growth of the fungus was found to be 7 to 9. Richards’ broth was found to be the best medium for the production of toxin followed by Czapek’s and Fries’ media. Exotoxin production was found to be more than endotoxin. The toxic metabolite is found to be thermostable. Diluting the culture filtrate to 4 times its volume showed a reduction in the toxic effect. However, the treatments did not completely eliminated the toxic effect of the preparation. The toxic effect of the culture filtrate translocated by defoliation on the cut twigs of plants. Culture filtrate of the fungus inhibited the spore germination of Colletotrichum glocosporioides and Curvularia sp. The culture filtrate as well as the mycelial extract produced lesions on clove leaves of different maturity, with pronounced effect on tender leaves. Spore germination of the fungus could be completely inhibited with all the eight fungicides in all concentrations on the first day of observation. Daconil-2767, Dithane M-45, Fytolan and Thride were able to cause 94,97,94 and 95 per cent inhibition of spore germination respectively upto 12th day at maxium concentration tested ( 3000 ppm). Growth of the fungus was completely inhibited with Bavistin 250, 500 and 1000 ppm, Dithane M-45 1000, 2000 and 3000 ppm; Mildothane 500, 1000 and 2000 ppm and thride 1000, 2000 and 3000 ppm; when tested in czapeks’ agar medium. In czapeks’ solution Bavistin, Difolatan, Dithane M-45 and Mildothane at all concentrations tested, there was complete inhibition of growth of the fungus. Bavistin at 250 ppm and Thiride at 1000 ppm were able to inhibit the growth of the fungus by 15 minutes immersion, when the culture dises were tested for the viability of the fungus, Mildothene and Dithane M-45 inhibited the growth of the fungus at 1000 and 2000 ppm respectively, When the culture discs were tested for the viability of the fungus after immersion for one hour in fungicidal solution. Fytolan and Difolaton were able to inhibit the growth of the fungus at the maximum concentration (both at 3000 ppm), only after 24 hours immersion in the fungicidal solution.Item Transition to organic agriculture in Kasaragod district: A multi dimensional analysis(Department of Agricultural Extension, College of Horticulture, Vellanikkara, 2016) Seenu Joseph; Jiju P AlexItem Studies on the effect of fungicides and silica in the control of sheath blight of rice caused by Corticium Sasakii (Shirai) Matsumoto(Division of Plant Pathology, College of Agriculture, Vellayani, 1975) Mathai, G; Paily, P VA field experiment to determine the effect of two fungicides under three levels of silica on the incidence and intensity of sheath blight of rice was conducted at the Agricultural College Farm, Vellayani during the crop season February to May 1974. The fungicides, hinosan and dithane M-45, were effective in reducing the intensity, per cent infection and rate of spread of the disease and thereby increasing the yield. Among the fungicides tried hinosan was significantly superior. Application of silica was found to have significant effect in reducing the intensity of the disease on the 75th day. However, the per cent infection, rate of spread and the intensity on the 85th day indicated that the effect of silica in imparting resistance to infection by the pathogen was not significant.Item Symptomatology etiology and control of sheath rot disease of rice caused by Acrocylindrium oryzae(Department of Plant Pathology, College of Agriculture, Vellayani, 1981) Balakrishnan, B; Chandrasekharan Nair, MSheath rot disease of rice caused by Acrocylindrium oryzae was investigated. The fungus was found to infect rice plants at boot leaf stage. The leaf sheath covering the panicle was found to be comparatively more susceptible to the fungus than the sheath of other leaves. Severe infection caused choising of the whole penicle insids the sheath itself before emergence. The pathogen was isolated from infected tissues of host plants and brought into pure culture. Comparative studies of air isolates of Acrocylindrium oryzae from four rice varieties and two weed hosts did not show much appreciable difference in their morphological characters except light variations in the hyphal thickness and smaller conidial size from those on weed hosts.Item Characterization and management of powdery mildew of yard long bean (vigna unguiculata subsp.sesquipedalis (L.) verdc.) under protected cultivation(Department of Plant Pathology, College of Horticulture, Vellanikkara, 2018) Rahila Beevi, M H; Sainamole Kurian, PYard long bean (Vigna unguiculata subsp. sesquipedalis (L.) Verdc.) is believed to be selected and developed from cowpea (Vigna unguiculata (L.) Walp.) for its long, succulent pods which are used as a vegetable. In Kerala, it is one of the most preferred vegetables having very high amount of protein, iron, calcium, vitamin A, Vitamin C and dietary fibre. It is considered as a remunerative crop under protected condition owing to its high market demand. However, incidence of diseases is a major setback hampering the production of yard long bean under protected conditions among which, powdery mildew is the most devastating one. In this background, the present study was undertaken to characterize the pathogen causing powdery mildew of yard long bean and to formulate a management strategy for the disease under protected cultivation. Purposive sampling surveys were conducted in seven locations of Thrissur district and the disease severity varied from 1.67 to 67.33 per cent. The results of the survey indicated that the severity of disease was more during pod bearing and harvesting stage. Since powdery mildews are obligate parasites, characterization was done based on the microscopic observation of pathogen present on the leaves. The fungi produced hyaline, branched and septate hyphae. The conidiophores were erect and cylindrical on which conidia were born in chains. Variability was observed regarding conidia and conidiophore characters of powdery mildew collected from different locations, based on which the isolates were grouped into two viz., PM 1 and PM 2. PM1 type was observed in all locations except Vellanikkara. Based on the morphological characteristics of conidia and conidiophores, it was identified as Erysiphe polygoni. PM 2 type obtained only from Vellanikkara in which conidia and conidiophore characters were similar to Podosphera sp. which is very rarely reported on legumes. Hence, its identity was further confirmed as Podosphaera xanthii by molecular characterization. The rRNA-ITS sequence was deposited in NCBI Genbank database with accession number MH645799. This is the first report of powdery mildew of yard log bean incited by Podosphaera xanthii. In-vitro evaluation of 17 treatments including fungicides, biocontrol agents and botanicals by spore germination technique revealed that all the treatments caused cent per cent inhibition of conidial germination. For taking forward eight promising treatments to the field experiments, they were tested in-vitro on detached leaves by artificial inoculation of conidia from infected leaves. Based on the per cent leaf area infected, two systemic fungicides, one contact fungicide, two biocontrol agents and one botanical were selected for field evaluation. Field experiments were conducted simultaneously inside polyhouse and rain shelter to evaluate the performance of selected fungicides, biocontrol agents and botanicals against powdery mildew. Among the treatments, low disease severity of 4.33 per cent and 7.67 per cent was recorded in T1- difenoconazole and T2 – tebuconazole respectively in polyhouse and these treatments were statistically on par. In rain shelter also, T1- difenoconazole and T2- tebuconazole recorded low disease severity of 7.67 per cent and 10.67 per cent respectively. The performance of wettable sulphur at lower and higher concentration did not differed significantly. All the four non-chemical treatments were equally effective in managing the disease both in polyhouse and rain shelter. Correlation analysis between the meteorological parameters and disease severity revealed that per cent disease severity was negatively correlated with temperature and relative humidity both in polyhouse and rain shelter. Analysis of population of phylloplane microflora showed that, there was a drastic reduction in the population of phylloplane fungi and bacteria after spraying chemical fungicides which is an indication of the toxicity and non-selectivity of these chemicals. Survival ability of biocontrol agents sprayed on the leaves were studied and found out that both Trichodema viride and Pseudomonas fluorescens survived on the leaves for seven days. Residue analysis of difenoconazole, the most effective chemical fungicide revealed that the compound with initial deposition of 0.21 mg kg-1 dissipated to 0.09 mg kg-1 after seven days in polyhouse whereas, the residue after seven days in rain shelter was 0.19 mg kg-1. The faster degradation of the chemical inside polyhouse may be attributed to the higher temperature prevailed during the experiment. Evaluating the results various experiments in the present investigation, it was found that, even though chemical fungicides provided best disease control, considering their toxic effect on beneficial non target microflora on the phylloplane and the residue left on edible pods, biocontrl agents such as Trichoderma viride and Pseudomonas fluorescens which exhibited consistent performance with moderate disease control and sufficient survival on the leaf surface would be ideal to control powdery mildew of yard long bean if applied at right time. Moreover, frequent application of systemic fungicides with single site action can result in the development of resistant strains of pathogens. So such chemicals should be adopted only if the disease severity is very high and cannot be managed with biocontrol agents.Item Identification and management of mycoflora associated with grain discolouration of rice (oryza sativa L.)(Department of Plant Pathology, College of Horticulture, Vellanikkara, 2018) Aswathi, M S; Raji, PItem Cataloguing, documentation and management of fungal diseases of strawberry (Fragaria x ananassa Duch.)(Department of Plant Pathology, College of Horticulture, Vellanikkara, 2017) Amrutha, P; Reshmy VijayaraghavanItem Characterization and management of fungal pathogens of cabbage (Brassica oleracea var. capitata L.) and cauliflower (Brassica oleracea var. botrytis L)(Department of Plant Pathology, College of Horticulture, Vellanikkara, 2017) Nusrath Beegum, C H; Yamini Varma, C KItem Post harvest deterioration of fruits by microbes and their control(Department of Plant Pathology, College of Agriculture, Vellayani, 1987) Anita Cherian, K; Susamma PhilipSeveral 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