Title page for ETD etd-10052005-123519

Document Type Master's Dissertation
Author Joubert, Carinne
URN etd-10052005-123519
Document Title Rhizobia associated with Australian Acacia species ( Acacia mearnsii, Acacia dealbata and Acacia decurrens ) in South Africa as determined by sodium dodecyl-sulphate polyacrylamide gel electrophoresis
Degree MSc (Microbiology)
Department Microbiology and Plant Pathology
Advisor Name Title
Prof P L Steyn Committee Chair
Mr S N Venter Committee Co-Chair
  • nitrogen fixation
  • acacia South Africa roots physiology
  • rhizobium
Date 2003-04-01
Availability unrestricted
The projected exponential growth of the human population necessitates a concomitant increase in food supplies, and by implication an increase in fixed nitrogen for crops and pastures. This can to a large extent be supplied by biological nitrogen fixation (BNF). However, to achieve this goal improved effectivity of the legume-rhizobium symbiosis is required, implicating improvement in the macro- as well as the micro symbiont. Therefore the search for more effective microsymbionts is a sine qua non to provide better matching and tolerance to stress conditions.

The aim of this study was to investigate the range of rhizobia associated with the exotic Australian Acacia species (A. meamsii, A. dealbata and A. decurrens) in South Africa and to determine whether these species could be useful to provide rhizobial strains for application in the South African inoculant industry in order to improve local existing biological nitrogen-fixing systems. Although these Acacia species are geographically widespread throughout South Africa, their root nodule bacteria have never been investigated in depth. Their widespread occurrence and presumed promiscuity suggested that they might form nitrogen-fixing symbioses with a wide range of indigenous rhizobial strains with different ecological adaptations.

In this study nodulated plants of the three Acacia spp. were collected from diverse geographic areas with diverse climatic conditions and different soil pH's. Isolates were obtained from root nodules, purified and the putative rhizobial isolates characterized with sodium dodecyl-sulphate polyacrylamide gel electrophoresis (SDS-PAGE), supplemented at the genomic level with 16S rDNA sequence data of selected isolates.

The majority of the isolates investigated were members of the genus Bradyrhizobium, whilst some isolates showed close relationships to the genera Agrobacterium, Mesorhizobium, Rhizobium and Sinorhizobium. As a result of their predominant association with the slow-growing strains of the genus Bradyrhizobium, the legume spp. A. meamsii, A. dealbata and A. decurrens as trap plants would not playa significant role as a source of diverse rhizobia for application in the South African inoculant industry.

2002 University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria.

Please cite as follows:

Joubert, C 2002, Simulation of a building heating, ventilating and air-conditioning system, MSc(Agric) dissertation, University of Pretoria, Pretoria, viewed yymmdd < http://upetd.up.ac.za/thesis/available/etd-10052005-123519/ >


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