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Subject: Plant Pathology × Author: S.B.Mallesh × End date: 2018 × Type: Thesis × Thesis Type: Ph.D ×
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    ThesisItemOpen Access
    Plant growth promoting rhizobacteria , their characterization and mechanisms in the suppression of soil borne pathogens of coleus and ashwagandha
    (UAS, Dharwad, 2008) S.B.Mallesh; S.Lingaraju
    Major coleus and ashwagandha growing districts of Karnataka were surveyed for the prevalence of wilt/root-knot complex in these crops. Survey revealed the association of Fusarium chlamydosporum, Ralstonia solanacearum and Meloidogyne incognita with coleus and ashwagandha. As many as fifty native plant growth promoting rhizobacterial (PGPR) strains from healthy coleus and ashwagandha rhizospheres were isolated, maintained and screened in vitro against F. chlamydosporum, R. solanacearum and M. incognita causing wilt/root knot complex. Of them 19, 17 and 17 strains were respectively found to be highly potent antagonists: Among these strains seven highly effective strains commonly inhibitory to all the pathogens were selected and characterized as Pseudomonas spp. and used further. When assessed for their mechanism of biocontrol, these potent antagonists produced at least one antimicrobial antibiotic, siderophore, HCN, IAA, fluorescien, pyocyanin and volatile metabolites. Molecular variability through RAPD-PCR showed highest (84 per cent) similarity between rhizobacterial strains RB31 and RB50, though these were isolated from geographically diverse locations. A greenhouse experiment was conducted to assess the plant growth promotion and vigour index by potent antagonists in coleus and ashwagandha. Talc-based bioformulations were prepared for the promising strains and their efficacy was tested under pot and field conditions. Bioformulations containing PGPR strains were evaluated against species of Fusarium, Ralstonia and Meloidogyne (either individually or in combination) for their efficacy to reduce the disease incidence and induced systemic resistance in coleus and ashwagandha under glasshouse condition. Among the various bioformulations, strains RB50 and RB31 were found to be effective in increasing plant growth parameters, viz. plant height, number of branches, fresh and dry weight of shoot and root, length of root, yield of coleus and ashwagandha plants and also in decreasing number of galls (RKI) and disease incidence in glasshouse and field conditions.
  • Thumbnail Image
    ThesisItemOpen Access
    Plant growth promoting rhizobacteria , their characterization and mechanisms in the suppression of soil borne pathogens of coleus and ashwagandha
    (UAS Dharwad, 2008) S.B.Mallesh; S.Lingaraju
    Major coleus and ashwagandha growing districts of Karnataka were surveyed for the prevalence of wilt/root-knot complex in these crops. Survey revealed the association of Fusarium chlamydosporum, Ralstonia solanacearum and Meloidogyne incognita with coleus and ashwagandha. As many as fifty native plant growth promoting rhizobacterial (PGPR) strains from healthy coleus and ashwagandha rhizospheres were isolated, maintained and screened in vitro against F. chlamydosporum, R. solanacearum and M. incognita causing wilt/root knot complex. Of them 19, 17 and 17 strains were respectively found to be highly potent antagonists: Among these strains seven highly effective strains commonly inhibitory to all the pathogens were selected and characterized as Pseudomonas spp. and used further. When assessed for their mechanism of biocontrol, these potent antagonists produced at least one antimicrobial antibiotic, siderophore, HCN, IAA, fluorescien, pyocyanin and volatile metabolites. Molecular variability through RAPD-PCR showed highest (84 per cent) similarity between rhizobacterial strains RB31 and RB50, though these were isolated from geographically diverse locations. A greenhouse experiment was conducted to assess the plant growth promotion and vigour index by potent antagonists in coleus and ashwagandha. Talc-based bioformulations were prepared for the promising strains and their efficacy was tested under pot and field conditions. Bioformulations containing PGPR strains were evaluated against species of Fusarium, Ralstonia and Meloidogyne (either individually or in combination) for their efficacy to reduce the disease incidence and induced systemic resistance in coleus and ashwagandha under glasshouse condition. Among the various bioformulations, strains RB50 and RB31 were found to be effective in increasing plant growth parameters, viz. plant height, number of branches, fresh and dry weight of shoot and root, length of root, yield of coleus and ashwagandha plants and also in decreasing number of galls (RKI) and disease incidence in glasshouse and field conditions.