Thumbnail Image

Theses

Browse

1980 - 198110
Reset filters
Subject: Plant Pathology × Author: KAU × End date: 1981 × Start date: 1980 × Thesis Type: M.Sc ×
Reset filters

Search Results

Now showing 1 - 9 of 10
  • Thumbnail Image
    ThesisItemOpen Access
    Studies on the phyllosticta leaf spot of ginger
    (Department of Plant Pathology, College of Horticulture, Vellanikkara, 1981) Premanathan, T; KAU; Peethambaran, C K
    Laboratory and field experiments of “The studies on the Phyllosticta leaf spot of ginger” were conducted at the College of Horticulture Campus, Vellanikkara during 1979-1981. The first visible symptom of the disease was observed as chlorotic specks. Fructification was more during the later stages of crop growth. The detailed study on the plant and environmental factors influencing the disease development in the field revealed that the average number of leaves per plant has a significant positive correlation with the disease intensity. Koch’s postulate and morphological studies proved that the pathogen causing the disease is Phyllosticta zingiberi Ramakr. Uninjured leaves and first three leaves, even after injury, failed to exhibit the symptoms on inoculation. Conidia germinated by putting forth single or double germtubes. Sucrose solution (1,000 ppm) supported faster and maximum spore germination and the bipolar germination noted was maximum in this solution. The fungus entered the leaf by direct penetration of epidermal cells without appressoria formation. The pycnidiospores and mycelia of the pathogen were found to survive even after seven months in soil under different depths and moisture conditions. The type Maran was found to be the least susceptible followed by Karakkal and Bajpai, whereas type Vengara was the most susceptible one. Out of the 12 fungicides tried, one per cent Bordeaux mixture and 2,000 ppm Bayer 5072 gave cent per cent inhibition of the fungal growth in both solid and liquid media. Antracol 2,000 ppm and panolil above 500 ppm in solid medium; bavistin 2,000 ppm and cuman above 500 ppm in liquid medium gave cent per cent inhibition of fungal growth. In the field trial cuman, was found to be the most effective fungicide in controlling the disease, followed by Bordeaux mixture and panolil. Maximum rhizome yield was noticed in cuman treated plots followed by Bordeaux mixture.
  • Thumbnail Image
    ThesisItemOpen Access
    Studies on the control of soft rot of ginger
    (Department of Plant Pathology, College of Horticulture, Vellanikkara, 1980) Kurucheve, V; KAU; Peethambaran, E K
    The present investigation ‘Studies on the control of soft rot of ginger’ was conducted at the Instructional Farm, attached to College of Horticulture, Vellanikkara, Trichur during the year 1978-79. Two varieties of ginger viz. ‘Rio-de-janeiro’ and ‘Maran’ were used for the investigations. The objectives of the investigations were 1) to find out the causal organism of soft rot of ginger in the acid lateritic soils of Vellanikkara 2) to find out suitable control measures against the disease 3) to know whether the fungus could develop resistance against continuous application of fungicides and 4) to find out any adverse effect on the development of ginger rhizomes when the fungicides were applied for controlling the disease. The pathogen responsible for the disease was found to be Pythium aphanidermatum (Edson) Fitzpatrick. More than 90 per cent inhibition of the fungus was observed by agallol, thiride and difolatan at 500 ppm concentration in vitro. Hundred per cent inhibition of the fungus was possible only with 2000 ppm of Cheshunt compound or thiride and with 500 ppm of agallol in vitro. Among the different combinations of Cheshunt compound, agallol and thiride, 100 ppm of agallol plus 100 ppm of thiride was the most effective combination in inhibiting the mycelial growth of the fungus. Seed treatment with 0.25 per cent agallol solution alone was not effective in reducing the disease incidence in the field. The fungicides which were proved very effective in in vitro studies, were again tested under field conditions. They were Cheshunt compound, agallol and thiride. Soil drenching before planting with the above mentioned fungicides reduced the pre emergence rotting considerably. Single application of fungicides either in one, three or four months after planting was not adequate in controlling the disease. A minimum of two post emergence applications i.e. One month and three months after planting either with cheshunt compound or agallol, in addition to pre planting soil drenching were necessary for controlling the disease as well as for getting good yield. P. aphanidermatum did not develop any resistance against the fungicides when they were applied continuously in the field. Adverse effect on the development of ginger rhizomes was not noticed when the fungicides were applied for controlling the soft rot of ginger. The present investigation showed that extent of control varied with the sequence and number of fungicidal applications. Treatments agallol – cheshunt compound, cheshunt compound – cheshunt compound and cheshunt compound – agallol in two times application; cheshunt compound – cheshunt compound – cheshunt compound ; cheshunt compound – agallol – thiride and cheshunt compound – thiride – agallol in three times application and cheshunt compound – cheshunt compound – cheshunt compound – cheshunt compound; agallol – agallol – agallol – agallol and cheshunt compound – thiride – agallol – cheshunt compound in four times application showed a better disease reduction compared to other treatments. The post emergence rotting started appearing from July and peak infection was noticed during August. The variety ‘Maran’ was more resistant to the disease. There was a direct correlation between the disease incidence and continuous rainfall.
  • Thumbnail Image
    ThesisItemOpen Access
    Studies on the leaf blight disease of clove caused by Cylindrocladium sp.
    (Department of Plant Pathology, College of Agriculture, Vellayani, 1980) Sulochana, K K; KAU; Chandrasekharan Nair, N
    Leaf 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.
  • Thumbnail Image
    ThesisItemOpen Access
    Seed mycoflora of some vegetables in Kerala
    (Department of Plant Pathology, College of Agriculture, Vellayani, 1981) Naseema, A; KAU; Balakrishnan, S
    The survey of the seed mycoflora of vegetable seeds revealed the presence of a number of seed-borne fungi. Storage fungi like Aspergillus flavus, Aspergillus niger Penicillium sp. and Rhizopus stolonifer were found to be externally as well as internally seed-borne , in almost all the vegetable seeds taken for the study. A part from these , other fungi like Curvularia lunsta. Fusarium equlecti and Myrothecium roridum from amaranthus , Botryodiplodia theobrease from bhindi, bitter gourd and cowpea, Fusarium oxysporum and Eectria haemtococca from bhindi, Achaetonium macrosporum and Collstrotrichum lagenarium from bitter gourd, Drechalera rostrata from cowpea, Cephaliophora irregularis and Fusarium solani from pumkin were obtained. The seed-borne fungi were found to cause inhibitory effect on the germination of the seeds , from which they were isolated , Maximum inhibition in the germination was found to be caused by storage fungi like Aspergillus flavus, Aspergillus niger. Penicillium sp. and Rhizopus stolonifer . Rotting of the seedlings was caused by Fusarium equiseti on amaranthus, Prechslera rostrata on cowpea . Aspergillus niger and Rhizopus stolonifer on tomato.
  • Thumbnail Image
    ThesisItemOpen Access
    Etiology and control of bacterial leaf blight of rice caused by Xanthomonas oryzae (Uyeda and Ishiyama) Dowson
    (Department of Plant Pathology, College of Agriculture, Vellayani, 1980) Mary, C A; KAU; James Mathew
    The bacterial leaf blight of rice, incited by Xanthomonas oryzae (Syeda and Ishiyama) Dowson is one of the most serious disease of economic importance in India and several other rice growing countries of the world. This disease was first reported in India by Sreenivasan et. al. (1959) from Maharashtra and a serious epiphytetic was reported by Srivastava and Rao (1963) from Bihar. In Kerala , eventhough severe epiphytotics of this disease have not been reported so far, the disease is endemic in the major rice growing areas of Kuttanad and Palghat. The pathogen was identified as Xanthomonas oryzae (Uyeda and Ishiyama) Dowson based on its morphological , cultural , physiological and biochemical characters together with its pathogenicity. For laboratory studies and mass culturing of the organism, Glucose Yeast extract Agar and Glucose Agar were found to be the best solid media and Glucose Yeast extract chalk broth and potato Sucrose Peptone broth were the best liquid media. The pathogen was found to survive in infected seeds for a period of 90 days , in infected debris in soil for a period of 28 days and in infected soil for less than a week indicating that the infected seeds and infected plant debris in soil play an important role in the epidemiology of the disease.
  • Thumbnail Image
    ThesisItemOpen Access
    Etiology of the bacterial wilt of ginger incited by Pseudomonas solanacearum E.F. Smith and its control
    (Department of Plant Pathology, College of Agriculture, Vellayani, 1980) Marykutty Samuel; KAU; James Mathew
    The bacterial wilt of gingerincited by psuedomonas solanacearum E.P. Smith probably the most serious of all the disease recorded on this crop was first reported from India in 1978. The symptoms of the disease include loss of turgidity of leaves , rolling and yellowing of the leaflets, cropping and wilting of the plant and rotting of the rhizome . No variations in symptoms were observed with the different inclates of the pathogen. Nutrient agar and peptone ceramic acid were the best soild media for the growth of the bacterium . Slight variations in growth were observed among the isolates when grown on ECA medium. The pathogen was identified to be Pseudomonas solanacearum E.P. Smith , biotype -3 of Hayward, from its morphological , physiological and biochemical characters coupled with pathogenicity.
  • Thumbnail Image
    ThesisItemOpen Access
    Role of weeds in the perpetuation of virus diseases of vegetables and ornamental plants
    (Department of Plant Pathology, College of Agriculture, Vellayani, 1981) Mathew, A V; KAU; Balakrishnan, S
    Virus diseases affecting ten different weed plants and their possible role in the perpetuation of virus diseases of certain cultivated plants were investigated. These ten weeds were affected by 13 virus diseases. All the 13 viruses were transmitted by wedge grafting. Among the 13 viruses studied, 3 viruses, viz., mosaic of Amaranthus viridis yellow mosaic of Micrococca mercurialis and mosaic Stachytarpheta indica were transmitted by sap inoculation and by insect vectors. Eight viruses, viz., yellow vein mosaic of Ageratumconizoides, leaf curl of A. conizoides, yellow vein mosaic of Croton sparsiflorus and Sida cordifolia, yellow mosaic of Micrococca mercurialis, leaf curl of Stachytarpheta indica and Synedrella nodiflora and yellow mosaic mottle of Stachytarpheta indica var. jamaicensis were transmitted by the whitefly, Bemisia tabaci Genn.
  • Thumbnail Image
    ThesisItemOpen Access
    Role of the rice root nematode (Hirschmanniella oryzae) in the incidence of sheath blight disease of rice in Kerala
    (Department of Plant Pathology, College of Agriculture, Vellayani, 1981) Gokulapalan, C; KAU; Chandrasekharan Nair, M
    Rhizoctonia solani causing sheath blight of rice was found to infect a number of common weeds and crops raised in rice fallows in Kerala. The fungus was found to produce leaf and stem blight in groundnut plants. This is the first report of this fungus causing serial blight symptoms in adult groundnut palnts. On Sesbania aculeata (daincha), the fungus produce severe collar rot, this being the first record of this fungus on this crop in India. The occurrence of R.solani under natural conditions on the weeds, Anluda aristata and Monochoria vaginalis are reported for the first time.
  • Thumbnail Image
    ThesisItemOpen Access
    Studies on the bacterial leaf spot of betel vine incited by Xanthomonas betlicola Patel et al.
    (Department of Plant Pathology, College of Agriculture, Vellayani, 1980) Koshy Abraham; KAU; James Mathew
    The bacterial leaf spot of betel vine incited by Xanthomonas betlicola Patel et al. is one of the most serious diseases recorded on the plant and was first reported in the year 1951. The occurrence and severity of the disease in Kerala was reported from 1978 onwards. The symptoms of the disease is characterised by water soaked lesions, bacterial exudations, dark brown patches with yellow halo, marginal infection, shot hole type symptoms, defoliation, stem and petiole infection. Minor variations in the above symptoms were observed with different isolates of the pathogen.