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2001 - 200712
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Subject: Plant Pathology × End date: 2009 × Start date: 2000 × Thesis Type: Ph.D ×
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Now showing 1 - 9 of 12
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    ThesisItemOpen Access
    Influence of VAM inoculation on nutrient uptake, growth, yield and bacterial wilt incidence in tomato (Lycopersicon esculentum Mill.)
    (Department of Plant Pathology, College of Horticulture, Vellanikkara, 2002) Raji, P; KAU; Sukumara Varma, A
    An investigation on the influence of VAM inoculation on nutrient uptake, growth, yield and bacterial wilt incidence of tomato (Lycopersicon esculentum Mill.) was carried out at the College of Horticulture, Vellanikkara during the period 1996 - 2000. The objectives of the study were to select an efficient VAM fungus for improving nutrient uptake, growth and yield of tomato, to explore the possibility of reducing the use of phosphorus fertilizer by VAM inoculation and also to study its influence on bacterial wilt incidence. The survey conducted revealed the natural occurrence of VAM association in tomato at different locations of Kerala. There was variation in VAM colonization and rihzosphere spore count among the locations. Predominant VAM fungi associated with tomato at the survey locations belonged to the genus Glomus. Out of the fifteen native isolates and four standard cultures, Glomus mosseae, Glomus fasciculatum, Glomus intraradices and Gigaspora margarita, the native isolate collected from Eruthempathi (Palakkad District) was found to be the best in improving nutrient uptake, growth and yield of tomato variety, Sakthi. Inoculation of this isolate resulted in increased root colonization, spore count, shoot and root biomass, root volume and yield. It induced seven days early flowering and increased the ascorbic acid content of the fruit. The uptake of nutrients particularly P, K and Ca was improved by the inoculation of this isolate. The pot culture experiment conducted to study the possibility of reducing phosphorus fertilizer due to VAM inoculation showed the superiority of VAM isolate collected from Eruthempathi in improving growth, P uptake and yield. With the increase in dose of P upto 50 per cent, there was a significant increase in root colonization, fresh weights and dry weights of shoot and root and also the yield. No further increase in these parameters was recorded with the increase in dose of P upto 100 per cent. The plants inoculated with the VAM isolates along with 50 per cent P recorded shoot and root biomass and yield significantly superior to that of these parameters recorded by the plants which received full dose of P alone. The results of the field experiment showed that the plants inoculated with VAM had higher root colonization and rihzosphere spore count compared to uninoculated plants. Irrespective of the form of P used the rihzosphere spore count and VAM colonization were less at higher doses of P compared to lower doses. Among the treatments involving super phosphate, the treatment T9 (VAM + FYM + N + 50% SP + K) was significantly superior in improving root colonization, spore count, fresh weight and dry weight of root, root length, shoot P content and yield compared to the package of practices recommendations (T2 - FYM + N + SP + K). Among the treatments involving mussorie rock phosphate, the treatment Tio (VAM + FYM + N + 75% MP + K) was significantly superior to the present package of practices recommendations in its effects on fresh weight and dry weight of shoot and root, root length, shoot P content and yield. The nutrient status of the soil with respect to P_ and K content was improved by the treatment T9 (VAM + FYM + N + 50% SP + K). No significant change in soil P content was observed by the VAM inoculation along with MP. The treatment Tio (VAM+FYM+75%MP+K) recorded the highest soil K content. The field experiment conducted in the wilt sick field revealed that inoculation of selected VAM fungi could reduce the bacterial wilt incidence. Among the three varieties tested viz., Sakthi, BWR-1 and Pusa Ruby, a significant reduction in bacterial wilt incidence due to inoculation of VAM fungi collected from Eruthempathi was recorded by the variety, Sakthi. The inoculated plants of BWR-1 showed only five per cent reduction in wilt incidence. No reduction in wilt incidence was observed in variety, Pusa Ruby.
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    ThesisItemOpen Access
    Plant growth promoting rhizobacteria mediated induced systemic resistance against bacterial wilt in ginger
    (College of Horticulture, Vellanikkara, 2007) Reshmy, Vijayaraghavan; KAU; Koshy, Abraham
    The pathogen causing bacterial wilt of ginger was isolated and identified as Ralstonia solanacearum biovar III based on its cultural, morphological and biochemical characters coupled with pathogenicity. Rhizosphere microflora of ginger from different locations of Thrissur, Waynad and Palakkad districts were isolated. Altogether, 163 rhizobacterial isolates were selected from these areas and their antagonistic activity against the pathogen assessed. Out of 163 isolates, only 45 showed antagonistic reaction. Further, study of these antagonists based on zone of inhibition resulted in selection of 20 isolates. The effect of these 20 isolates in promoting the growth of ginger was studied in pot culture in comparison with three reference cultures of P. fluorescens and B. subtilis. Result of this experiment revealed that only 11 isolates including the two reference cultures of P. fluorescens had growth promoting effect as evidenced in terms of yield and yield attributing characters of ginger. Factors which impart growth promotion in ginger by these isolates were assessed by estimating the inhibition zone, vigour index, hydrogen cyanide, indole acetic acid, ammonia production and ‘P’ solubilzation and based on that, PGPR index of the isolates was worked out. In addition to that, production of salicylic acid, antibiotics and siderphore by the isolates, the secondary metabolites which are known to play a role in disease suppression were assessed. The isolates varied in their ability to produce salicylic acid. Isolates RB-22 followed by RB-11, RB-144 and RB-66 produced more number of antibiotics which include pyoluteorin, pyrrolnitrin, 2,4DAPG etc. Similarly, isolate RB-22 and RB-11 produced maximum siderophores. The potential of these 11 rhizobacterial isolates in imparting resistance against the disease was assessed in another pot culture experiment by estimating phenol, proteins and amino acid content of ginger upon challenge inoculation. Here also, the isolates showed a profound effect on growth and yield of ginger especially by those plants bacterized with RB-11. There was no natural incidence of bacterial wilt in plants treated with RB-11 and RB-22. Upon challenge inoculation also, plants bacterized with RB-11 showed the least incidence. In general, rhizobacterial treated plants contained more amount of phenol, protein and amino acids than untreated ones. Upon challenge inoculation with the pathogen, the rate of increase of these compounds in rhizobacteria treated plants was more than that of control during different intervals of observations. A third pot culture experiment was conducted to assess the effect of rhizobacterial treatments on defense related enzymes of ginger upon challenge inoculation. Here, eight most promising ones including the reference cultures were used. In general, the study revealed more activity of peroxidase (PO), polyphenol oxidase (PPO) and phenylalanine ammonia lyase (PAL) in rhizobacterial treated plants that too after challenge inoculation. Native PAGE analysis revealed six isoforms of PO and four isoforms of PPO in a majority of the rhizobacterial treated plants whereas only three were noticed in control. Similarly, difference in the protein profile of rhizobacterial treated plants and control was noticed. Chlorophyll, NPK and oil and oleoresin content varied among treatments where the highest was observed in rhizobacterial treated plants. An attempt was made to elucidate the molecular mechanism of induced systemic resistance (ISR) in ginger by synthesizing cDNA and was subjected to RAPD assay. However, no conclusive evidence on ISR was observed. The compatibility of eight rhizobacterial isolates including the two reference cultures with antibiotics, fungicides, insecticides and fertilizers were assessed which revealed variation in their sensitivity. Moreover, mutual compatibility of the rhizobacterial isolates and compatibility with Trichoderma spp. were also studied and it was observed that all bacterial isolates were mutually compatible. However, Pseudomonas aeruginosa, P. fluorescens (RB-66) and the reference culture of P .fluorescens (P.f2) were found incompatible with the Trichoderma spp. The promising six rhizobacteria isolates were identified based on cultural, morphological and biochemical characters and also in comparison with that of reference culture of P. fluorescens. They were tentatively identified as Pseudomonas aeruginosa (RB-22), Pseudomonas fluorescens (RB-82, RB-66, RB-11) and the remaining two, RB-144 and RB-77, as non-fluorescent Pseudomonads.
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    ThesisItemOpen Access
    Management of pumpkin mosaic using selected medicinal plant extracts
    (Kerala Agricultural University;Thrissur, 2003) Louis, Vimi; KAU; Sukumara Varma, A
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    ThesisItemOpen Access
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    ThesisItemOpen Access
    Management of water hyacinth [Eichhornia crassipes (Mart.) Solms] using fungal pathogens
    (Kerala Agricultural University;Thiruvananthapuram, 2003) Praveena, R.; KAU; Naseema, A.
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    ThesisItemOpen Access
    Strain improvement and production technology of milky mushroom (Caiocybe indica P. and C.)
    (Kerala Agricultural University;Thiruvananthapuram, 2006) Heera, G; KAU; Suharban, M.
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    ThesisItemOpen Access
    Purification and immunodetection of banana bract mosaic virus
    (Kerala Agricultural University;Thiruvananthapuram, 2004) Dhanya, M.K.; KAU; Rajagopalan, B.
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    ThesisItemOpen Access
    Characterization, host range and management of sweet potato feathery mottle virus
    (Kerala Agricultural University;Thiruvananthapuram, 2001) Jeeva, M.L.; KAU; Balakrishnan, S.
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    ThesisItemOpen Access
    Disease management and growth improvement in chilli and tomato using Trichoderma spp. and fluorescent pseudomonads
    (Kerala Agricultural University;Thiruvananthapuram, 2005) Rini, C.R.; KAU; Sulochana, K.K.