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Subject: Agricultural Microbiology × Thesis Type: Ph.D ×
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Now showing 1 - 9 of 36
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    ThesisItemOpen Access
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    ThesisItemOpen Access
    Isolation, Characterization and Screening of Gluconacetobacter diazotrophicus From Various Crops and Their Influence on Growth and Yield of Maize (Zea Mays L.)
    (University of Agricultural Science, Dharwad, 2017-05) Rao, Hema C.; Savalgi, V.P.
    A total of 113 isolates of Gluconacetobacter diazotrophicus isolated from sugarcane, maize, pineapple and carrot roots through survey from Dharwad, Belagavi, Uttara Kannada, Haveri and Shivamogga districts of Karnataka during 2014, were characterized morphologically, physiologically and biochemically and subjected for in vitro nitrogen fixation which ranged between 14.01 to 147.1 µg mg-1. The highest N2 was fixed by the native isolate NFGS25 (147.1 µg mg-1). Twenty best isolates were screened for further functional characterization viz., P and Zn solubilization, phytohormone production, antagonistic activity and endoglucanase activity. The zone of solubilization of P and Zn (3.1 and 2.5 cm), IAA and GA production (11.54 and 10.1 µg ml-1) and endoglucanase activity (86 µg ml-1) were maximum in NFGS25. The highest per cent inhibition was exhibited by NFGS25 against Rhizoctonia bataticola (83.33%) and Exserohilium maydis (88.86%). Five best isolates (NFGS25, NFGS26, NFGM5, NFGM6 and NFGP7) were selected for screening of growth parameters and N uptake of maize in the pot trial. The results revealed that plant height, stem girth, root length, chlorophyll content, dry weight, per cent N and N uptake were significantly highest in the treatment inoculated with NFGM5 at 75 % RDN followed by NFGS25 at 75% RDN. The population of G. diazotrophicus was maximum in the treatment NFGM5 at 75 % RDN (7 x 104 cfu ml-1). Based on their performance in pot trial, two efficient isolates (NFGM5 and NFGS25) were selected for field trial and confirmed as G. diazotrophicus isolates by molecular characterization. The results of the field experiment conducted during kharif 2016 at MARS, Dharwad, revealed that all the growth and yield parameters (number of cobs, cob weight, grain yield per plant and test weight) were significantly highest in the treatment NFGM5 at 75% RDN followed by NFGS25 at 75% RDN. The maximum grain yield of 183.33 q ha-1 (15% higher than control) was observed in the treatment NFGM5 at 75 % RDN which was better than the reference strain Azospirillum ACD15 with 75% RDN. Thus it is evident that the inoculation of native isolates of G. diazotrophicus (NFGM5 and NFGS25) at 75% RDN promotes better growth, grain yield and saves nitrogenous fertilizer up to 25% of recommended dose in field condition.
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    ThesisItemOpen Access
    APPLICATION METHODS OF VA MYCORRHIZAL INOCULUM FOR CROPS IMPORTANT IN AGRICULTURE, HORTICULTURE AND FORESTRY
    (University of Agricultural Sciences, Dharwad, 1999) G, MAMATHA; BAGYARAJ, D J
    ABSTRACT NOT AVAILABLE
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    ThesisItemOpen Access
    SELECTION OF RHIZOBACTERIA ANTAGONISTIC TO Ralstonia solanacearum E.F. Smith CAUSING BACTERIAL WILT IN TOMATO AND THEIR BIOCONTROL MECHANISMS
    (University of Agricultural Sciences, Dharwad, 2000) JAGADEESH, K S; KULKARNI, J H
    "As many as 431 native rhizobacterial isolates of tomato were screened in vitro on KB medium for the inhibition of Ralstonia solanaceamm causing bacterial wilt disease. Of them, 38 strains were found to be potent antagonists with the zone of inhibition of the pathogen varying from 8-20 mm dia., and 23 of them were fluorescent pseudomonads. When assessed for mechanism of biocontrol, all the potent antagonists produced at least one antibacterial metabolite: antibiotics, siderophores, or HCN. Twenty-five strains were found to be antibiotic producers, 23 (only fluorescent pseudomonads) were siderophore producers, 12 were HCN producers, 13 were both antibiotic and siderophore producers, nine were both antibiotic and HCN producers, 12 were both siderophore and HCN producers and nine strains produced all the three metabolites. In the greenhouse experiment, Sid and Sid'' mutants obtained by the Tn5 mutagenesis of fluorescent Pseuodurnonas strains RBL 101 and RSI 125, failed to control the disease as much as their wild type did, thus confirming fluorescent siderophore production as the mechanism of biocontrol in these strains. The greenhouse experiments revealed that 27 antagonistic strains were found to be plant growth promoting (PGPR). The PGPR strains produced copious amounts of plant growth promoting substances viz., lAA and GA. Thirteen rhizobactcrial strains were found to be deleterious (DRB), producing unidentified gaseous metabolilcs. 'I'he unusual poor growth and biomass of tomato in the UIC plants was due to the predominance of twice deleterious histosphere bacteria (DHB). However, the PGPR strain fluorescent Pseuodurnonas RDV 108 inhibited DHB and nullified its inhibitory effect. The fluorescent Pseuodurnonas strain RDV 107 was found to be the best bio control agent with a percent disease control of 77.30 besides exhibiting good root colonization ability, plant growth promotion and siderophore and antibiotic production. "
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    ThesisItemOpen Access
    STUDIES ON Azospirillum ISOLATES OF ORNAMENTAL PLANTS AND THEIR EFFECT ON Gaillardia pulchella var picta Fouger
    (University of Agricultural Sciences, Dharwad, 1999) GADAGI, RAVI; KULKARNI, J H
    Investigations were carried out on the isolation, identification, genetic diversity, screening of Azospirillum and their inoculation effect on the growth and flowering of Gaillardia. Attempts were made to improve the nitrogen-fixing efficiency of Azospirillum through mutagenesis. From the present investigation, it can be concluded that Azospirillum is common inhabitant of roots of ornamental plants. From the 88 isolations made, 55 percent of isolate were Azospirillum lipoferum while Azospirillum brasilense represented 41.57 percent. The nitrogen fixation by Azospirillum isolates in the semi-solid medium ranged from 1.40 (OAD-36 and OAD-72) to 20.54 (OAD-2) mg gi of malate. Further, ability- to fix dinitrogen was also confirmed by acetylene reduction assay. Although all the Azospirillum isolates could produce variable quantity of IAA and GA, Strain OAD-57 produced the highest plant growth-promoting substances. Genetic diversity of Azospirillum isolates was analyzed through intrinsic antibiotic resistance, protein and plasmid profile. The isolates showed wide diversity with respect to intrinsic antibiotic resistance. However, using the protein finger printing the two definite groups of Azospirillum could discerned. All the isolates contained only one plasmid (22 kb). Seven efficient isolates were selected for further field study, based on preliminary screening of all the isolates under pot culture. From the field experiment, it can be concluded that OAD-2 can play an important role in the N-nutrition of Gaillardia pulchella. Further 25 AziR and EDAR mutants were obtained through NTG mutagenesis. TShese mutants had higher nitrogenase activity and in vitro N fixed g-1 malate. The AziR OAD-904 and EDAR OAD-209 performed better than their respective wild type, in pot cultures in augmenting plant growth and N-uptake of Gaillardia pulchella.
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    ThesisItemOpen Access
    MINERAL PHOSPHATE SOLUBILIZATION BY BACTERIA AND THE ROLE OF PYRROLO QUINOLINE QUINONE (PQQ)
    (University of Agricultural Science, Dharwad, 1998) Dinesh Kumar, T K; Siddrame Gowda, T K
    ABSTRACT NOT AVAILABLE
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    ThesisItemOpen Access
    INFLUENCE OF VA MYCORRHIZAL FUNGI, AND NITROGEN FIXING AND MYCORRHIZATION HELPER BACTERIA ON GROWTH OF NEEM (Azadirachta indica A. Juss.)
    (University of Agricultural Science, Dharwad, 1998) Sumana, D A; Bagyaraj, D J
    ABSTRACT NOT AVAILABLE
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    ThesisItemOpen Access
    EFFECT OF PAPER MILL EFFLUENT IRRIGATION ON SOME CHEMICAL AND MICROBIOLOGICAL PROPERTIES OF SOIL
    (University of Agricultural Science, Dharwad, 1997) Vishwanth, N R; Bagyaraj, D J
    ABSTRACT NOT AVAILABLE
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    ThesisItemOpen Access
    THE ROLE OF ASSOCIATIVE CYANOBACTERIA IN NITROGEN FIXATION BY Azolla spp.
    (University of Agricultural Science, Dharwad, 1995) Tilak, Minakshisundaram; Shivappa Shetty, K
    ABSTRACT NOT AVAILABLE