Thumbnail Image

Theses

Browse

1990 - 199629
Reset filters
Subject: Plant Pathology × Author: KAU × End date: 1996 × Start date: 1990 × Thesis Type: M.Sc ×
Reset filters

Search Results

Now showing 1 - 9 of 29
  • Thumbnail Image
    ThesisItemOpen Access
    Associative effect of azospirillum and bradyrhizobium on nodulation and growth of cowpea (viqna unquiculata (l.) walp,
    (Department of Plant Pathology College of Horticulture Vellanikkara, 1992) Sunitha, Menon S.; KAU; Rajendran, Pillai M .V
  • Thumbnail Image
    ThesisItemOpen Access
    Leaf blight of banana and its control
    (Department of Plant Pathology, College of Agriculture, Vellayani, 1993) Saj, KV; KAU; Sulochana, K K
    Survey conducted to study the fungal pathogens causing leaf blight disease in banana in the three agricultural subdivisions of Thiruvananthapuram district, yielded seven fungal pathogens viz., colletotrichum musae, Curvularia sp, Guignardia musae, khuskia oryzae, Nodulisporium gregarium, Pestalotiopsis versicolor and Phaeoseptoria sp. Among these, Curvularia sp, Khuskia oryzae and Nodulisporium gregarium are new reports. Morphological characters and pathogenicity tests of all the seven isolated cultures were studied and described. Detailed studies were conducted on five fungal pathogens viz., C. musae, G. musae, K. oryzae, N. gregarium and Phaeoseptoria sp., since severe infections could be noticed by these fungi. Studies conducted on the growth and sporulation of pathogens on different, media indicated that Richard’s medium was the best for C. musae and G. musae, potato dextrose medium for K. oryzae and Phaeoseptoria sp. In the case of N. gregarium, potato dextrose agar and Czapek (Dox) broth were found to be the best solid and liquid media respectively for its growth. Best growth of C. musae, N. gregarium and Phaeoseptoria sp was obtained with maltose as the carbon source, whereas G. musae and K. oryzae utilized maximum starch and sucrose for their growth. Maximum mycelial weight of C. musae was obtained with sodium nitrate as nitrogen source, G. musae and K. oryzae with potassium nitrate, N. gregarium with glutamine and Phaeoseptoria sp. with asparagine. Potato dextrose broth and Richard’s solution were found to be best media for the toxin production by C. musae K. oryzae , G. musae and Phaeoseptoria sp. produced maximum toxin in Richard’s solution and N. gregarium in potato dextrose broth. Host range studies of the pathogen (s) conducted indicated that they can infect a number of economically important plants like, clove, cocoa, colocasia, nutmeg and tapioca, but none of the pathogens could infect clerodendron. Dithane M-45, calixin and Bavistin were able to inhibit the growth of the leaf blighting pathogens under laboratory conditions and under field conditions Dithane M-45 (0.2%) was found to be the best. Varietal screening trials showed that variety Rasakadali was moderately resistant/tolerant among the four popular varieties screened, whereas Nendran was the most susceptible variety.
  • Thumbnail Image
    ThesisItemOpen Access
    Vascular streak dieback of cocoa and its management
    (Department of Plant Pathology, College of Horticulture, Vellanikkara, 1996) Ajay Kumar, K M; KAU; Koshy, Abraham
    Vascular streak dieback (VSD) is a destructive disease of cocoa. Corticium culture medium, Water agar, Potato dextrose agar gave promising results in isolation of the pathogen. Petiole and midrib gave maximum success in isolation. Potato dextrose agar and Corticium culture media supported the growth of the fungus. Fusarium sp. And Colletotrichum gloeosporioides were the major contaminants interfering in the isolation of VSD. The morphological characters of the pathogen were studied from the sporophores occurring on naturally infected cocoa plants. Based on these characters, the pathogen causing VSD was identified as Oncobasidium theobromae Talbot and Keane. The disease produced various typical symptoms on leaves and stems of infected plants like pale green colour of leaves and subsequent yellowing with green islets, defoliation, brown marks on the scars of fallen leaves, axillary bud growth of the infected stem, rusty discolouration of cambium, vascular streak, whitish sporophores on the leaf scar of fallen infected leaves and finally the death of the infected twig. Histopathological studies showed the presence of fungal mycelium in the xylem vessels. Transmission studies by grafting and budding revealed no establishment of buds or grafts. But there was vascular streaking. No seed transmission was observed. In general Kitazin and Bavistin as a seed treatment had an effect on the height of plant and leaf production. Evaluation of cocoa types planted at three seed gradens indicated that some of them possess resistance/tolerance against VSD. Variation in disease incidence and intensity of VSD was noted in germplasm VI. Calixin spraying had an effect in preventing the incidence of the disease in seedlings.
  • Thumbnail Image
    ThesisItemOpen Access
    Combatibility of certain fungicides and insecticides used for the control of major diseases and insect pests infesting the rice crop
    (Department of Plant Pathology, College of Horticulture, Vellanikkara, 1992) Kalpana, T A; KAU; Sally Mathew, K
    The efficacy of four fungicides and four insecticides alone and in combination was studied at different concentrations recommended, three-fourth and half the recommended concentrations against two major diseases of rice namely, rice blast caused by Pyricularia oryzae Cavara and sheth blight caused by Rhizoctonia solani kahn. And two major insect-pests namely, leaffoldar Cnaphalocrocis medinalis medinalis Guen. And brown planthopper Nilaparvatha lugens stal. At tillering, panicle initiation and flowering stage of the crop. The experiment was conducted in vivo and in vitro conditions during 1989-91, at the college of Horticulture, Vellanikkara, Thrissur. In general combind application of fungicides and insecticides controlled the diseases and insect-pests more effectively than the treatments given separately. At tillering stage, a synergistic effect of fungicide was observed, when it was sprayed along with insecticides. Among different combinations tried, tridemorph (o.1 per cent) + monocrotophos (0.0375%) and carbendazim (0.075 ) + guinalphos (0.025 per cent) were the best combinations against blast and sheath blight respectively. In the case of leaffolder and brown planthopper, quinalphos was found to be the best insecticide, when used alone and also in combination with fungicides. At panicle initiation stage, combined sprays of higher concentrations of carbendazim and monocrotophos was the best combination in controlling both R. solani and N. lugeas. But ediphenphos-phosphamidon combination was found to be the superior against N. lugens. When combind spraying was given at flowering stage, captafol (0.225 per cent) + quinalphos (0.0375 per cent, and carbendazim (0.075 per cent) + monocrotophos (0.0375 per cent) were found to be the best combinations against P. oryzae and R. solani respectively. But, combination of recommended doses of quinalphos with tridemorph and ediphenphos and, phosalone with ediphenphos were the effective treatments in controlling C. medinalis and N. lugens respectively. In in vitro studies, a total inhibition of the test organisms, viz.P. oryzae and R. solani were observed in all the treatments. Whereas, in the case of C. medinalis recommended doses of quinalphos in combination with ediphenphos and carbendazim and phosalone with tridemorph recorded highest mortality; while, highest dose of quinalphos with captafol and phosalone with ediphenphos were the superior combinations against N. lugens. From the above findings it could be concluded that, the fungicides viz. ediphenphos, carbendazim, captafol and tridemorph are compatible with all the four insecticides tried viz. Phosphamidon, quinalphos, phosalone and monocrotophos in controlling the diseases, blast and sheath blight and insect pests leaffolder and brown planthopper.
  • Thumbnail Image
    ThesisItemOpen Access
    Etiology and control of seedling blight of cocoa
    (Department of Plant Pathology, College of Horticulture, Vellanikkara, 1995) Edwin Prem, E; KAU; Koshy, Abraham
    The seedling blight is a serious nursery disease of cocoa. The fungus causing seedling blight of cocoa was isolated and Koch’s postulates were established. On carrot agar medium, the fungus produced sparse, striate growth. The mature sporangia were near spherical to ovoid with round base, papillate, caduceus with an average L/B ratio of 1.74. Sporangia were borne terminally in a sympodial fashion. It had a short and thick stalk with an average length of 4.1µm. Based on these characters, the pathogen causing seedling blight of cocoa was identified as Phytophthora palmivora (Butler) Butler. For maximum growth of the fungus, oat meal and corn agar were the best. But, for maximum sporangial production, carrot agar and oat meal agar were good. Among the liquid media, oat meal and corn meal broth supported good growth of the fungus. The disease produced various type of symptoms on leaves and stem of seedlings and budded plants like water soaking, leaf blight, defoliation, black discolouration, cotyledonary infection, wilting and die back. Stem of budded plants were more prone to infection than that of seedlings. The seedlings blight pathogen infected plants such as Piper nigrum L., Cocos nucifera L., Hevea brasiliensis L., Bougainvillea sp. And Colocasia esculenta L. but did not infect Areca catechu L., Piper betle L. and Piper longum L. on artificial inoculation. The youngest seedlings of age group less than 18 days after germination were more vulnerable to infection. Similarly, the youngest budded plants of age group 45 days after budding showed maximum infection. Among the 62 cocoa types screened for host resistance the cocoa types GIV-36.6 (local), GVI-23 (P9 x P4), GIV-4.6 (local) and S-45.5 (local) showed minimum percentage of mortality. Among the different fungicides/antibiotics screened in in vitro, Fytolan, Captaf, Bordeaux mixture, Akomin and Ridomil at all concentrations and 0.3 per cent Foltaf and, Chloramphenicol and Terramycin each at 400 and 500 ppm completely inhibited the growth of the fungus. Indofil-M.45, Aureofungin and Amoxycillin exhibited less inhibitory effect. Foltaf, Fytolan and Akomin each at 0.3 per cent concentration showed better effect in cheching the lesion development on detached cocoa leaves. Result of the different in vivo control experiment indicated that, the fungicides like Akomin, Foltaf, Fytolan and Bordeaux mixture had promising effect in checking the incidence and severity of the disease.
  • Thumbnail Image
    ThesisItemOpen Access
    Symptomatology and etiology of little leaf disease of pepper (piper nigrum L.)
    (Department of Plant Pathology, College of Horticulture, Vellanikkara, 1995) Sree Kumari, P K; KAU; Sukumara Varma, A
    Symptomatology and etiology of little leaf disease of pepper (piper nigrum L.) was conducted at the department of plant pathology, College of Horticulture, Vellanikkara, Thrissur and at pulppally in Wayanad district during 1992-94. Based on the external symptoms of the disease a disease scoring chart (0 to 4) was perfected. The diseased plants had shorter main root and less number of feeder roots. Brown discoloration was noticed on diseased roots. Internodal length as reduced which give a bushy appearance to the plant. Leaves were distorted, downwardly curved, chlorotic, brittle with wire-net type vein lets. Enen though the size and shape were normal, the number of flowers per spike decreased and the aborted flowers increased. Proper maturity was obtained by very few berries. Disease was observed to attach all age group of plants, but the intensity increased with age. Variety karimunda was highly susceptible and punniyur-1 was observed to be tolerant though the disease attacked Arakkulam munda, Aimpiriyan and Vellananamban with lesser degree than karimunda. Application of zinc did not inhibit the symptoms. When 0.2% Dienes stain was used for the phloem portion of the roots, nodes and petioles of the diseased and healthy plants, only diseased plant parts stained blue indicating the presence of mycoplasma like organisms in them. Disease could not be transmitted by sap or dodder. It could be transmitted by cuttings and by wedge grafting using diseased root stock and healthy scion not vice versa. Transmission studies with insects Austroagallia sp. Manderan beta Owarokowska aand Liothrips Karnyi were not successful. Applications of oxytetracycline hydrochloride (OTC) by drenching, spraying, dipping and wick feeding were effective at concentrations more than 500 ppm for remission of disease symptoms. OTC at 250 ppm was not effective. Above 750 ppm, the treatment caused phytotoxicity. Among methods, wicks feeding was found to be the best, which prevented reappearance of symptom even after two years where as in all the other methods, the symptom remission lasted for less than 6 months. Yield was observed to be reduced with an increase in disease intensity. The study revealed the symptomatology of little leaf disease of black pepper and resulted in the identification of etiology as mycoplasma like organism.
  • Thumbnail Image
    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.
  • Thumbnail Image
    ThesisItemOpen Access
    Characterization and management of bacterial wilt of chillies caused by Pseudomonas solanaceasum E F Smith
    (Department of Plant Pathology, College of Horticulture, Vellanikkara, 1992) Jyothi, A R; KAU; Koshy Abraham
    Bacterial wilt is one of the most serious disease of chillies in Kerala. The pathogen was isolated from infected chilli plants and its pathogenicity established. Ten isolates of the pathogen viz., five from chillies , two each from tomato and brinjal and one from ginger were used in the study and they werre characterized and identified as blovar III of Pseudomonas solanacearum (Smith) Smith based on the morphological, cultural, biochemical and physiological characters, coupled with its pathogenicity. Twentynine accessions/varieties of chillies were screened for host resistance against bacterial wilt and the study revealed that the variety 'Manjari' (KAU Cluster/CA 33) was resistant to the disease. The accessions CA 205 and CA 207 exhibited moderately resistant reaction. There was no significant correlation between environmental factors and wilt incidence of all the accessions/varieties except CA 408, for which a positive correlation was noticed between soil moisture and wilt incidence.
  • Thumbnail Image
    ThesisItemOpen Access
    Compatibility of certain fungicides and insecticides used for the control of major diseases and insect pests infesting the rice crop
    (Department of Plant Pathology, College of Horticulture, Vellanikkara, 1992) Kalpana, T A; KAU; Sally, K Mathew
    The efficacy of four fungicides and four insecticides alone and in combination were studied at different concentrations (Recommended, three-fourth and half the recommended concentrations) against two major diseases of rice namely, rice blast caused by Pyricularia oryzae Cavarn and sheath blight caused by R hizoctonia solani Kuhn, and two major insect-pests namely, leaffolder Cnaphalocrocis medinalis Guen. and brown planthopper Nilaparvatha lugens Stal. at tillering, panicle initiation and flowering stages of the crop. The experiment was conducted in vivo and in vitro conditions during 1989-'91, at the College of Horticulture, Vellanikkara, Thrissur. In general, combined application of fungicides and insecticides controlled the diseases and insect-pests more effectively than the treatments given separately. At tillering stage, a synergistic effect of fungicide was observed, when it was sprayed along with insecticides. Among different combinations tried, triaemorpV. (0.1 per cent) + monocrotophos (0.0375%) and Carbendazim TO. 07‘5 % ) -:- quinalphos (0.025 per cent) were the best combinations against blast and sheath blight respectively. In the case of leaffolder and brown planthopper, quinalphos was found to be the best insecticide, when used alone and also in combination with fungicides. At panicle initiation stage, combined sprays of higher concentrations of carbendazim and monocrotophos was the best combination in controlling both R. solani and N. lugens. But ediphenphos-phosphamidon combination was, found to be the superior against N. lugens. When combined spraying was given at flowering stage, captafol (0.225 per cent) + quinalphos (0.0375 per cent) and carbendazim (0.075 per cent) + monocrotophos (0.0375 per cent) were found to be the best combinations against P. oryzae and R. solani respectively. But, combination of recommended doses of quinalphos with tridemorph and ediphenphos and, phosalone with ediphenphos were the effective treatments in controlling C. medinalis and N. lugens respectively. In in vitro studies, a total inhibition of the test organisms, viz. P. oryzae and R. solani were observed in all the treatments. Whereas, in the case of C. medinalis recommended doses of quinalphos in combination with ediphenphos and carbendazim and phosalone with tridemorph recorded highest mortality; while, highest dose of quinalphos with captafol and phosalone with ediphenphos were the superior combinations against N. lugens. From the above findings it could be concluded that, the fungicides viz. ediphenphos, carbendazim, captafol and tridemorph are compatible with all the four insecticides tried viz.; Phosphamidon, quinalphos, phosalone and monocrotophos in controlling the diseases, blast and sheath blight and insect pests leaffolder and brown planthopper.