Phenotypic characterization of rhizobia isolates and distribution of Burkholderia rhizobia in the Core Cape Subregion
Master Thesis
2016
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University of Cape Town
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The Core Cape Sub-region is well known for its low nutrient, low pH soils which harbour a variety of alpha and beta- Proteobacteria associated with a diversity of legume species. Soil bacteria are important for ecological processes and are influenced mostly by edaphic factors such as salinity and pH, and climatic conditions such as temperature. Recent studies have shown that Burkholderia form nitrogen fixing molecular associations with members of, among others, tribes Crotalarieae, Podalyrieae and Indigofereae. Selected rhizobia that included Burkholderia and Mesorhizobia, the large genera in the isolated rhizobia, and representing beta- and alpha- Proteobacteria were phenotypically characterized to determine the tolerances of Cape isolates to abiotic conditions. In a second study, glasshouse trapping experiments were conducted using legume species Podalyria calyptrata and Indigofera filifolia grown in 13 soils collected from diverse localities of the CCR, to determine the phylogenetic distribution of Burkholderia species in diverse soils of the CCR. To phenotypically characterize rhizobia isolated from a previous study, 29 isolates from representative legume-nodules of 13 different localities were grown under laboratory conditions. Isolates were phenotypically characterized for colony morphology, growth temperature, carbon source, salinity and pH tolerance. Morphological results revealed that majority of the tested isolates were white opaque, rod shaped and fast growing. Exceptions were found in colour where five strains produced a milky pigment, two were watery translucent; observation of bacteriod-shape among six symbionts; and one isolate grew after 7 days.
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Sinyanya, K. 2016. Phenotypic characterization of rhizobia isolates and distribution of Burkholderia rhizobia in the Core Cape Subregion. University of Cape Town.