PhD Thesis

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End date: 1989Subject: search.filters.subject.Plant Pathology

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Now showing 1 - 6 of 6
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    Deterioration of oil cake by fungi
    (Department of Plant Pathology, College of Agriculture, Vellayani, 1989) Naseema, A; Wilson, K I
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    Study of bacterial leaf spot of betel vine- biochemical changes and control
    (Department of Plant Pathology, College of Agriculture, Vellayani, 1986) Koshi Abraham; James Mathew
    The 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.
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    Studies on certain chemical constituents of banana leaves in relation to incidence of leaf spot diseases: A note on the fungi occurring on banana
    (Division of Plant Pathology ,Agricultural College and Research Institute ,Vellayani, Trivandrum, 1966) Chandrasekharan Nair, M K; Sam Raj, J
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    Studies on the burrowing nematode radopholus similis (cobb,1893) thorne 1949 on pepper(Piper nigrum L.) and its role in slow wilt disease
    (Department of plant pathology, University of agricultural sciences, Bangalore ., 1976) Venkitesan, T S; Setty, K G H
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    Symbiosis of rhizobium and VA mycorrhiza in subabul
    (Department of Plant Pathology, College of Agriculture, 1989) Rajendran Pillai, M V; Sasi Kumar Nair
    A survey was conducted at 17 locations in four districts of Kerala for natural nodulation and VA mycorrhizal infection in subabul. The survey revealed that natural nodulation and VA mycorrhizal infection were poor compared to inoculated plants. When all the 17 isolates of rhizobia and four cultures of VA mycorrhizal fungus were tested for effectiveness, the rhizobial isolate R8 and V AM fungus M2 were emerged as most efficient rhizobial and mycorrhizal cultures respectively. An in vitro study conducted revealed that in an acid PH of 6, the rhizobial isolate R8 survived better than other cultures. At pH 8, growth of another isolate R5 was found maximum. However, in an in vivo study, there was not much significance for the soil pH ranging from 6 to 7.1 in influencing various biometric parameters of subabul. In both the pH of 6 and 7.1, the performance of rhizobial isolate R5 and mycorrhizal culture M2 was best. Serological studies revealed that the exotic strains R18 R20 and and isolate from Mimosa indica had serological similarities with the best selected local isolate R8. Fine structure studies of nodules clearly showed the morphological differences between the uninfected nodular tissues and the infected central nodular tissue. The rhizobial infection transformed the normal cells into irregularly shaped cells within which numerous rhizobial cells were visible. In another observation, it was found that subabul plants starts to form nodules only from 15 days of sowing. There- after, the nodule number increased steadily attaining the peak at 70 days of growth and then remained more or less steady. Among various methods of inoculation of the microsymbionts tested, inoculation of both the microsymbionts at the time of sowing in polybag was found good for the better establishment of the plants in the field. In a field study, it was found that inoculation of the local isolate of Rhizobium R8 and mycorrhizal fungus M2 had great influence in increasing all the growth parameters. Standard mycorrhizal culture and local isolate performed equally well. Maximum forage yield was obtained when plants were inoculated with the selected local rhizobial isolate R8 and mycorrhizal fungus M2. Maximum mycorrhizal infection was also seen in the same treatment. Dual inoculation also had significant influence in increasing the leaf protein content. An important observation was that both rhizobial and mycorrhizal inoculation reduced the mimosine content of leaves. However, fertilizer nitrogen increased mimosine content. In short, dual inoculation by Rhizobium and VA mycorrhiza was found necessary for better establishment, growth and low mimosine content of subabul.
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    Studies on purple top roll (PTR) of potato in Karnataka
    (Department of Plant Pathology, University of Agricultural Sciences, Bangalore, 1983) Sreedharan, A; Reddy, H R
    1. Survey for the incidence of potato purple top roll revealed that the disease was present in Bangalore, Belgaum, Dharwad, Hassan and Kolar districts of Karnataka. The average percentage of incidence varied from 8.94 to 50.07. The survey also indicated that there was low incidence of the disease in summer and high incidence in kharif and rabi. 2. The pathogen was transmissible by wedge, side and core grafting. 3. The disease was transmitted through dodder, Cuscuta chinensis Lam. 4. The disease was not transmissible through sap and aphids Myzus persicae Sulz. And Aphis gossypil Glov. 5. The etiological agent was transmitted by the leafhopper, Orosius albicinctus Distant and not by Hishimonus phycitis Distant. 6. The vector, O. albicinctus could acquire the pathogen in two hr and inoculate to healthy plants in 30 min. The percentage of active transmission was 35 – 40 and the minimum incubation period in the plant was between 20 and 25 days. Maximum percentage of transmission was obtained on 40th day after inoculation. 7. Characteristic symptoms of the disease was inward rolling of basal parts of top leaflets, purple/pink pigmentation, smalling of leaves, excessive proliferation of axillary buds, erect appearance, production of purple coloured, aerial tubers and stunting and dwarfing of plants. 8. The etiological agent infected tomato, tree tomato, Datura stramonium and D. metel by grafting. 9. The pattern of spread of the disease in the field was from external source in the beginning and later the spread was within. 10. The vector population was correlated with the disease incidence in the field. The increase in the incidence of the disease followed the increase in the vector population. 11. The leafhopper vector, O. albicinctus Distant was high in the months from late June to December and low from January to early June. 12. The high population of leafhoppers was correlated with low temperature and high humidity and low population was correlated with high temperature and low humidity. 13. The disease appeared 40 days after planting in the field and then it gradually increased reaching the peak by 90th day. 14. The pathogen was transmitted through tubers for two successive generations but to a lower percentage in the second generation. 15. Of the 36 cultivars/varieties of potato tested under field conditions, none were found to be resistant, However, the vars. JF 542, JF 4612, JG 676, JG 900, JC 750 and JE 812 had less than five per cent infection. Kufri Chandramukhi and Kufri Jyoti were highly susceptible having 48.3 and 47.6 per cent incidence, respectively. The highest average incidence of PTR in these cultivars in farmer’s fields was 35.85 and 26.03 per cent, respectively. 16. There was considerable loss in yield in many cvs. Viz., JC 750, BS/F 100, JC 182 and EM/F 2120. 17. The weight of tubers produced by the infected plants was always less than the tubers obtained from the adjacent healthy plants. The infected plants produced more number of smaller tubers which aggregated close to the main stem attached on short stolons. 18. Complete remission was obtained at 500, 1000 and 2000 ppm, incomplete remission at 100 and 250 ppm and no remission at 50 ppm of tetracycline given alternatively for 20 days.