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Theses

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1990 - 19917
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Subject: Plant Pathology × End date: 1991 × Start date: 1990 × Thesis Type: M.Sc ×
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Now showing 1 - 7 of 7
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    ThesisItemOpen Access
    Bio-deterioration of important cucurbitaceous seeds due to mycoflora
    (Department of Plant Pathology, College of Horticulture, Vellanikkara, 1990) Saleena George; KAU; Cheeran, A B I
    The study "Bio-deterioration of important cucurbitaceous seeds due to mycoflora" was conducted at College of Horticulture, Vellanikkara. The objectives of this study were to find out the role of seed borne mycoflora on the bio-deterioration of important cucurbitaceous seeds, the variation in the seed mycoflora in different periods of the year, to assess the role of different humidity levels on the viability of seeds and to evolve a suitable management practice to prevent the bio-deterioration of seeds. The study revealed that the unsterilised seeds were found associated with mycoflora throughout the period of investigation . Mycoflora associated with surface sterilised seeds was less than that of unsterilised seeds. The maximum fungal association was found on the seed coat, then in the endosperm and least in the embryo in all the three vegetable seeds. Twentyseven species of fungi were found associated with bitter gourd seeds . Ten of them were external contaminants. Twentyfive species of fungi were obtained from the cucumber seed of which 11 species were found to be externally seed borne fungi were Aspergillus sp., Pencillium sp. and Rhizopus sp. while among the internally seed borne fungi the predominant ones were Fusarium solani, Aspergillus flavus and Rhizopus stolonifer.
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    ThesisItemOpen Access
    Standardisation of food bases for selected antagonistic microflora against soil-borne pathogens
    (Department of Plant Pathology, College of Horticulture, Vellanikkara, 1990) Mini, S Nair; KAU; Nair, P V
    Techniques for mass multiplication and production of antagonistic microflora isolated from the forest soils of Kerala for the biocontrol of soil-borne pathogens viz., Rhizoctonia, Pythlum and Phytophthora were investigated. The antagonists used were Trichoderma harzianum, T, Ionqibrachiatum, Aspergillus terreus, Panicillium citrinum, P.simplicissimum and Bacillus subtillis. The food bases tried were rice, wheat bran, paddy straw, rice bran, cowpea, forest soil and soil + dried.cowdung. The growth and survive! of antagonists in various food bases were estimated in vitro. A pot culture experiment was laid out during the period from March to September 1989 at the College of Horticulture, Vellanikkara to assess the population dynamics of the Introduced antagonists in rhizosphere of crop plants end to find out the effect of carrier based antagonist in controlling collar rot of cowpea caused by Rhizoctonia solani, soft rot of ginger caused by Pythium myriotylum and quick wilt of black pepper caused by Phvtophthora palmivora. Milled rice was found to be the most promising food base for all the isolates tested. Wheat bran was also found good for all the Isolates except T. longibrachiatum, T. longibrachiatum as well as B. subtilis were found to grow well in rice broil. A. terreus and P. citrlnum exhibited good growth while moderate growth of T. longibrachiatum and P. simpliciasimum was observed with cowpea as a food base. In general paddy straw, forest soil and soil + cowdung was found to be poor substrates compared to other food bases. But in paddy straw, T. harsianum ,A. terreus. P. citrinum and B. subtilis survived better compared to other food bases.
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    ThesisItemOpen Access
    Bio-deterioration of important vegetable seeds due to mycoflora II
    (Department of Plant Pathology, College of Horticulture, Vellanikkara, 1991) Ambika, S; KAU; Jose, P C
    Bio-deterioration of important vegetable seeds due to mycoflora-II" was studied at the Department of Plant Pathology, College of Horticulture, Vellanikkara during the year 1988-89. Three vegetable seeds viz., bhindi (Abelmoschus esculentus (L.) Moench), cowpea Vlqna unquiculata (L.l Walp) and dolichos bean (Dolichos 1ablab L .) were used for the investigations. The objectives of the investigations were 1. To assess the role of seed-borne mycoflora and bio-deterioration of important vegetable seeds (bhindi, cowpea and dolichos bean)2. To study the influence of seasons on the association of seed-borne mycoflora of stored vegetable seeds 3. To assess the effect of relative humidity on the viability of vegetable seeds 4. To study the role of seed mycoflora on the germination of seeds and 5. To find out the effect of fungicides to minimise the fungal bio-deterioration of stored vegetable seeds.
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    ThesisItemOpen Access
    Integrated management of sheath blight disease of rice
    (Department of Plant Pathology, College of Agriculture, Vellayani, 1990) Geogy Zacharia; KAU; Rajan, K M
    The present investigation was undertaken to evolve an economically feasible management strategy integrating biological and chemical aspects of control measures of sheath blight disease of rice. An attempt has been made to identify a potential biocontrol agent to combat sheath blight disease causing considerable loss to rice cultivation. Another important aspect of the programme was to develop and easy and cheap method of assaying the population of R. solani in paddy soil. Among different techniques screened, floatation sieving using both Fenwick can and glass cylinder were effective in selective recovery and the latter was further modified using different concentrations of salt. Among selective media mineral antibiotic media amended with Fosetyl-al and in studies using different baits autoclaved straw bits were superior. Among the microorganisms isolated from rice soils of Thiruvananthapuram, Kerala, thirteen species of fungi were found to be antagonistic to R. solani. Among the antagonists, Trichoderma harzianum was found to be the best biocontrol agent against sheath blight disease. This was followed by T. koningii. A field study incorporating various soil amendments viz., neem cake and lime, Carbendazim and T. harzianum, a combination of amendments with Carbendzim and T. harzianum reduced disease severity and increased yield of grain and straw. These combinations also showed higher fungal and bacterial population and reduced R. solani population. Negative correlation between total fungi/bacteria and R. solani was observed suggesting inoculums reduction of the pathogen in critical growth stages of the crop. From the economic point of view, lime alone was found to have highest cost- benefit ratio compared to other treatments. The above result is possibly due to poor disease pressure observed during the investigation
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    ThesisItemOpen Access
    Effect of 2-bromo-2-nitro propaine-1, 3-diol and cowdung extract on growth and virulence of Xanthomonas campestris pv. oryzae
    (Department of Plant Pathology, College of Agriculture, Vellayani, 1991) Sreekumar, C T; KAU; Sasikumar Nair
    The present investigation was taken up to assess the efficacy of two alternative control methods, spraying with bactrinol-100 and cowdung extract in controlling bacterial blight of rice. An attempt was also made to elucidate the factor present in cowdung extract responsible for the control of bacterial blight pathogen. The pathogen was isolated from an infected rice field in kuttanad and tested for sensitivity to antibiotics, bactrinol-100 and cowdung extract under vitro conditions. Under in vitro conditions, terramycin 500 ppm was found to be most efficient in checking the growth and virulence of the pathogen followed by 250 ppm terramycin and 500ppm bactrinol-100. Cowdung extract failed to produce a typical growth inhibition zone. Subsequently the pathogen was inoculated in T(N)1- rice plants raised in pots, the disease was induced and the plants were sprayed with antibiotics, bactrinol-100 and cowdung extract. Under pot culture conditions terramycin 500 ppm reduced the disease intensity to the maximum followed by 500 ppm bactrinol-100. Cowdung extract was found to be better than some of the chemical treatments like terramycin 100 ppm, streptocycline 100, 250 and 500 ppm and bactrinol-100 at 100 and 250 ppm. Under field conditions 500 ppm terramycin gave maximum disease control at both the locations after the first and second spray. The grain yield was found to be maximum after spraying with 500 ppm terramycin at both the locations. The increase in thousand grain weight was found to be maximum in plants sprayed with cowdung extract in jyothi variety and in plants sprayed with 500 ppm bactrinol-100 in C-153 rice variety. Maximum reduction in chaffy grains was achieved after spraying with 500 ppm terramycin at both the locations. Straw yield was maximum in plants sprayed with 100 g/1 of cowdung extract in jyothi variety and in plants sprayed with 500 ppm terramycin in c-153 variety. So it is evident that unless appropriate control measures for bacterial blight are taken in time, significant yield losses can occur in rice varieties like jyothi and c-153. Spraying cowdu ng extract may be very useful to control bacterial blight especially when the disease incidence is mild. It can also be given as a prophylactic spray which may reduce the severity of the disease. These hypotheses have to be proved conclusively by further filed trails. The mode of inhibition of x. campestris pv.oryzae appeared to be due to an overgrowth of the pathogen mainly by bacteria and probably by some fungi present in cowdung extract. On working out the economic aspects of controlling bacterial blight it was observed that economic return was maximum after spraying infected plants with 100 g/1 cowdung extract followed by 500 ppm bactrinol-100. So economically it appears, that the use of cowdung extract or bactrinol-100 would be ideal to control bacterial blight of rice.
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    ThesisItemOpen Access
    Etiology and control of blight and fruit rot of brinjal
    (Department of Plant Pathology, College of Agriculture, Vellayani, 1991) Jenny John; KAU; Suharban, M
    The present investigation was undertaken to evolve an economically feasible management practice against the fruit rot and twig blight of brinjal. Infected plant parts of brinjal showing initial stages of infection were collected from different localities and symptomatology of the pathogen was studied in detail. The pathogen was brought into pure culture and sent to C.M.I. International Mycological Institute, U.K. for identification. It was identified to be Phomopsis vexans (Sacc. & Sydow.) Harter. Pathogenicity of the fungus was studied by inoculating the fruits and stems of the host plants and typical symptom similar to natural conditions were observed. Host range of the pathogen was studied by inoculating the different vegetables with the test fungus. Only carrot and tomato was found susceptible to the pathogen. The fungus grew well equally on potato dextrose host extract and oat meal media followed by Czapek’s and Richards’s media. Good sporulation of the fungus was also noticed in potato dextrose and host extract media, fair sporulation in oat meal and Czape’ks media and no sporulation in Richards’s media. In some cases wavy growth of the pathogen was noticed in potato dextrose agar. In liquid media good mycelia growth of the fungus was observed in potato dextrose, host extract and Czapek’s followed by oat meal and Richard’s media. Culture filtrate of the fungus caused drying of the leaves of the young seedling kept dipped in it and on leaves of matured plants it developed dark brown spots and these leaves dried up eventually. Seed treatment with culture filtrate exerted an inhibitory effect on germination of seeds of brinjal, chilli, tomato and greengram, whereas germination percentage was above 90 in seeds kept in sterile water. There was no difference in germination of seeds treated with culture filtrate fresh and that which was boiled for 10 minutes. The germination of seeds greatly reduced in seeds extracted from infected fruits both in blotter and sand method whereas the germination percentage of seeds extracted from healthy fruit was above 90 per cent. The seedlings raised from infected fruit showed damping off symptom after 2 weeks. Laboratory evaluation of different fungicides revealed that all the fungicides could inhibit the growth of the pathogen. Bordeaux mixture gave complete inhibition of growth of fungus at 750 ppm concertation while bavistin had the same effect at 500 ppm concentration. In field evaluation with different fungicides to control Phomopsis fruit rot it was found that spraying with CoC-50 at fortnightly interval was the best fungicide as the per cent infected fruits were minimum, that is 3.9, followed by Bordeaux mixture, dithane M-45, kavach, calixin, bavistin, and cumin L, with per cent infected fruits being 8.95, 10.7, 14.64, 15.35, 17.04, 20.56 respectively. Seeds of brinjal when soaked in spore suspension for 24 hours showed a reduction in germination compared to those seeds soaked in sterile water for the same period. Seed treatment with different fungicides showed that bavistin was the best fungicide in inhibiting the effect of the pathogen on seed germination followed by dithane M-45, and COC -50.
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    ThesisItemOpen Access
    Inhibitory effects of certain plant extracts on the incidence of cowpea mosaic
    (Department of Plant Pathology, College of Agriculture, Vellayani, 1990) Mallika Devi, S; KAU; Rajagopalan, B
    The inhibitory effect of certain plant extracts on the incidence of cowpea mosaic was studied. Preliminary screening of non-host plants for antiviral property against cowpea mosaic virus revealed that extracts of sixteen plants viz. Adenocalyma allicea, Azadirachta indica, Boerhaavia diffusa, Bougainvillea spectabilis, Calotropis gigantean, Clerodendron inflortunatum, Curcuma longa, Eupatorium odoratum, Ferrula indica, Mirabilis jalapa, Moringa Olifera, Phyllanthus niruri, Polyalthia longifolia, solanum indicum, Thespesia populnea and Vitex negundo inhibited the production of local lesions on the leaves of Chenopodium amaranticolor indicating that these extracts possessed antiviral property. The extracts of A. Indica, B. diffusa, B. spectabilis, C. gigantean, C. infortunatum, C. longa, M. jalapa, P. niruri, S. indicum, and V. negundo caused 100 per cent inhibition of the production of local lesions on C. amaranticolor even at five per cent concentration. The inhibitory effect of the plant extracts was found to be less pronounced when tested on the primary leaves of cowpea seedlings. Pre - inoculation application of plant extracts was found to be more effective than post-inoculation application in checking the incidence of cowpea mosaic. In insect transmission studies with Aphis craccivora cent per cent inhibition of disease incidence was obtained with the extracts of A. indicum, C. infortunatum, P. niruri and V. negundo. Studies on the effect of plant extracts on the acquisition and transmission of cowpea mosaic virus by A. craccivora revealed that the extract of P. niruri caused 100 per cent reduction over control. Maximum inhibition of disease development was obtained in plants inoculated with cowpea mosaic virus upto two days after the application of extracts of A. indica, P. niruri, V. negundo and C. infortunatum. Extracts of V. negundo and A. indica caused considerable reduction in the survival of A. craccivora on cowpea. The present studies indicated that, the extract of C. infortunatum had some systemic effect against cowpea mosaic virus. Repeated application of plant extracts on cowpea plants revealed that V. negundo had the maximum inhibitory effect on symptom development, in both sap and insect transmission trials. Height and weight of plants, number and weight of pods and root nodules of cowpea plants treated with plant extracts were found to be more than that of the control.