Systematics, Specificity, and Ecology of New Zealand Rhizobia

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dc.contributor.advisor Susan Turner (University of Auckland) en
dc.contributor.advisor John Young (Landcare Research) en
dc.contributor.advisor Warwick Silvester (Waikato University) en Weir, Bevan en 2007-04-01T21:59:52Z en 2007-04-01T21:59:52Z en 2006 en
dc.identifier.citation Thesis (PhD--Biological Sciences)--University of Auckland, 2006. en
dc.identifier.uri en
dc.description.abstract This research investigated the rhizobia that are associated with New Zealand legume plants. Rhizobia are a diverse group of bacteria that live in symbiosis with legumes in root nodules. Rhizobia fix Nitrogen from the atmosphere and provide this nutrient to the plant. The objectives of this research were to: 1) Determine the identity of the rhizobial species nodulating the native legumes of New Zealand: Sophora (kowhai), Carmichaelia (NZ broom), and Clianthus (kakabeak); and the identity and origin of rhizobial species nodulating invasive exotic legumes in New Zealand: Ulex (gorse), Cytisus (broom), and Acacia (wattles). 2) Determine the specificity and nitrogen fixing capacity of both groups of rhizobia. 3) Investigate the possible exchange of transmissible symbiotic genetic elements. A polyphasic strategy was used to determine the identity of bacterial isolates. The 16S rRNA, atpD, recA, and glnII genes were PCR amplified and sequenced, then analysed by maximum likelihood and Bayesian methods. Phenotypic characters were also assessed by use of the Biolog and FAME techniques. Nodulation and fixation ability was assessed by inoculating legume seedlings with rhizobial strains, then determining nitrogenase activity after ten weeks by gas chromatography, and examining roots for nodules. A gene involved in symbiosis, nodA, was sequenced from rhizobial strains to determine if transmission between strains had occurred. The results of the experiments showed that the native legumes were predominately nodulated by diverse Mesorhizobium spp. that contain three different nodA genotypes (two of which are novel) that have transferred between rhizobial strains. The Mesorhizobium spp. showed little nodulation specificity and could nodulate an exotic legume Astragalus (milk vetch), but not the invasive weed legumes. Rhizobium leguminosarum was also found to nodulate native legumes, albeit ineffectively. The exotic invasive woody legumes of this study were nodulated by diverse Bradyrhizobium spp. that had nodA genotypes typical of Australian and European species. The origins of these bacteria can not be categorically determined. However the evidence is presented to suggest that nodulating Mesorhizobium spp. arrived with the ancestors of the native legumes, while Bradyrhizobium spp. nodulating Ulex and Cytisus arrived recently from Europe. Bradyrhizobium spp. nodulating Acacia may be recently introduced, possibly from Australia, although further work is required to confirm these hypotheses. en
dc.description.sponsorship This study was supported by a grant from the Marsden Fund of the Royal Society of New Zealand, under contract 97-LAN-LFS-002, and a grant from the Non-Specific Output Fund of Landcare Research. en
dc.language.iso en en
dc.publisher ResearchSpace@Auckland en
dc.relation.ispartof PhD Thesis - University of Auckland en
dc.relation.isreferencedby UoA1707492 en
dc.rights Items in ResearchSpace are protected by copyright, with all rights reserved, unless otherwise indicated. en
dc.rights.uri en
dc.subject rhizobia en
dc.subject native legumes en
dc.subject microbiology en
dc.subject mesorhizobium en
dc.subject bradyrhizobium en
dc.subject kowhai en
dc.subject sophora en
dc.subject rhizobium en
dc.title Systematics, Specificity, and Ecology of New Zealand Rhizobia en
dc.type Thesis en Biological Sciences en The University of Auckland en Doctoral en PhD en
dc.subject.marsden Fields of Research::270000 Biological Sciences::270400 Botany en
dc.rights.holder Copyright: The author en
pubs.local.anzsrc 06 - Biological Sciences en Faculty of Science en

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