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Subject: Plant Pathology × End date: 2009 × Start date: 2009 × Type: Thesis × Thesis Type: Ph.D ×
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    ThesisItemOpen Access
    Variability and Management of Charcoal Rot of Sorghum Caused By Macrophomina phaseolina(Tassi) Goid
    (UAS Dharwad, 2009) Virupaksa.H.Prabhu; S.S.Adiver
    Charcoal rot of sorghum caused by Macrophomina phaseolina, is a severe disease particularly in rabi season grown crop. Thirty five infected sorghum stalk samples were collected from Karnataka, Maharashtra and Andhra Pradesh to assess the variability. Based on colony pigmentation, the cultures were assigned to four major groups on PDA and three groups on Czapek’s medium. Studies on toxin variability showed the symptoms such as drooping of leaves, blackening of leaves which was initiated at four hours and continued upto fourteen hours, thus revealing the existence of variation among the isolates. The sensitivity of isolates to copper sulphate at three different levels of concentrations found to differ to various concentrations tested. But with Carbendazim, the growth of all isolates were completely inhibited. Highest growth was observed in 7.0 pH, closely followed by 6.5 pH indicating preferential range to be between 6.5 and 7.00 pH. Peroxidase and Polyphenoloxidase enzyme analysis indicated that there was significant variation among the 35 isolates of M. phaseolina. RAPD data distinguished the 35 isolates into three major clusters. Management of charcoal rot of sorghum revealed that the seed treatment with carbendazim and seed treatment with T. harzianum + P. fluorescens showed superior results. Sixty four germplasm lines of sorghum screened. Charcoal rot was least in Dagadi Solapur, followed by GRS-1 and BCR-9. None of the genotypes showed resistant reaction. Employment of new source of resistance sources like local genotypes mentioned above can be effectively employed in resistance breeding programme to manage charcoal rot of sorghum.
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    ThesisItemOpen Access
    Epidemiology and management of bacterial blight of pomegranate caused by Xanthomonas axonopodis pv. punicae (Hingorani and Singh) Vauterin et al.
    (UAS Dharwad, 2009) S.T.Yenjerappa; V.B.Nargund
    Considering the magnitude and resultant losses due to bacterial blight in pomegranate, investigations were undertaken on disease, pathogen, environment and management aspects. Survey revealed the highest disease incidence in Chitradurga, Anantapur and Koppal districts and lowest incidence and severity was recorded in Bellary district. The bacterium was rod shaped, gram negative and capsulated. It was positive to starch hydrolysis, gelatin, liquefaction and H2S production. Modified D-5 medium was found superior in supporting the growth of the pathogen. Cultural variability among the 20 different isolates revealed the variability in growth and colony characters. The isolates exhibited 100 per cent polymorphism for OPA20, OPB03, OPF07 and OPF10 primers showing significant molecular variability. Among the different seasons, mrigbahar was found most vulnerable and hastbahar was found relatively safe in avoiding the disease. Rainfall for a longer period, maximum temperature between 29.4-35.60C and minimum temperature between 19.5 to 27.30C, RH of 63-87 per cent were found favourable for the disease development and spread. Pathogen survived upto 20 to 22 and 18 to 20 weeks in the infected residues buried in sterilized and unsterilized soil conditions, respectively. Neem, tridax and achyranthes were the alternate hosts for the pathogen. Bordeaux mixture 1% spray was very effective in reducing the initial inoculum of the pathogen. In vitro and in vivo evaluation of bactericides indicated that bronip (0.05%) + COC (0.2%) was highly effective in managing the disease with higher yield levels. In biological control, Bacillus subtilis, Pseudomonas fluorescens and garlic extract (10%) were significantly effective in reducing the disease. Application of multinutrients (1%) recorded the lower incidence and severity of the disease. The IDM strategy evaluated was found successful and feasible in managing the disease than farmers’ method of disease control.
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    ThesisItemOpen Access
    Epidemiology and integrated management of Anthracnose of greengram
    (UAS Dharwad, 2009) Sunil A.Kulkarni; V.I.Benagi
    major diseases of greengram. Survey work revealed that, the disease severity was found more in Bidar (49.43%) and least in Bijapur (23.86%) districts. The observations on loss estimation revealed that comparatively lower disease index and maximum BCR was recorded in plots receiving two sprays of carbendazim. The average grain yield loss of 40.18% and stalk yield loss of 46.90% was noticed due to anthracnose in unsprayed plots. The maximum mycelial weight was observed after 15 days of incubation. Solid medium like potato dextrose agar, liquid medium like Richard’s medium, temperature of 300C, RH of 95%, pH 6.5 and alternate cycles of light and darkness were found best for the growth and sporulation of C. truncatum. The spore load was maximum during last week of July and first week of August. The correlation studies between spore load, PDI and weather parameters indicated a negative correlation with temperature, while positively correlated with relative humidity and rainfall. The greengram crop sown on 4th June showed least disease severity. C. truncatum was survived upto 360 days in infected seeds and also in infected leaves stored under freeze condition. The flowering stage was found susceptible to the disease development. In host range studies only blackgram and horsegram had shown infection. The genotypes TM-96-2 and TARM-18 were found resistant to anthracnose. Further, comparatively lesser sugar and higher phenol content were observed in these varieties than in susceptible variety. In vitro evaluation revealed that, propiconazole, carbendazim, thiophanate methyl, benomyl, hexaconazole and carbendazim + mancozeb were found effective. Among botanicals azadirachtin was effective. Among bioagents and ITKs Trichoderma harzianum and cow urine respectively were most effective. In the management study hexaconazole was found to be effective in control of the anthracnose with maximum BCR
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    ThesisItemOpen Access
    Investigations on mild strains and transformation of PRSV-CP gene in papaya
    (UAS Dharwad, 2009) Mallikarjun.Y.Kenganal; A.S. Byadgi
    Management of PRSV using pathogen derived resistance and cross protection was attempted. Roving survey was conducted in entire Karnataka and parts of Maharashtra to know the incidence of PRSV and for collection of mild strains under natural conditions. Northern Karnataka witnessed high range of PRSV incidence compared to southern. The average of all the districts ranged between 1.42 to 92 per cent. Other than Kodagu incidence was recorded in all the districts. In Maharashtra incidence ranged between 35.50 to 86.17 per cent. During survey 16 mild strains were collected and evaluated for cross protection ability but, none of them proved as mild. Mutation of local PRSV-UASD strain using UV irradiation, sodium salts, sodium azide and EMS was also unsuccessful. Coat protein of PRSV-UASD CP gene (864bp) was cloned in Agrobacteruim tumefaciens for plant transformation. An in vitro regeneration in papaya was attempted by direct regeneration and somatic regeneration. Neither the explants nor the growth regulators in any treatments were successful. Embryo culture was attempted using embryos excised from immature seeds formed after 95 to 115 days of anthesis developed highest callus induction. Shoots regenerated from callus clump but, did not survive further. The PRSV-CP gene was cloned in Agrobacterium and cocultivated with papaya callus. It regenerated in to putataive transformants on kanamycine selective medium but, did not elongate further. Construct of PRSV-UASD-CP was finally transformed in to tobacco. In PCR and one step RT-PCR, amplicon of 864bp was evident of expression of transgene at transcriptional level. The PCR positive tobacco plants were challenged with PRSV-UASD strain. They remained healthy for 70 days without any viral symptoms, indicating successful expression of PRSV-UASD-CP gene conferring resistance to PRSVUASD inoculation.