‘Candidatus Liberibacter’ in four indigenous Rutaceous species from South Africa

Show simple item record

dc.contributor.advisor Pietersen, Gerhard
dc.contributor.coadvisor Steenkamp, Emma Theodora
dc.contributor.postgraduate Viljoen, Ronel
dc.date.accessioned 2014-07-30T07:40:27Z
dc.date.available 2014-07-30T07:40:27Z
dc.date.created 2014-04-09
dc.date.issued 2014 en_US
dc.description Dissertation (MSc)--University of Pretoria, 2014. en_US
dc.description.abstract Greening disease in South Africa is associated with a phloem-limited member of the Alphaproteobacteria known as ‘Candidatus Liberibacter africanus’ (Laf). Spread of this bacterium is assisted by the flight and feeding activities of its triozid vector, Trioza erytreae. In addition to Laf, ‘Candidatus Liberibacter africanus subsp. capensis’ (LafC) has been described from this country. LafC is widely associated with Calodendrum capense, an indigenous Rutaceous species. This dissertation aims to determine (i) whether reservoir hosts exist for Laf amongst indigenous rutaceous species that also act as native hosts to T. erytreae and (ii) whether LafC can be transmitted vertically through Ca. capense seeds. To achieve the first aim, a total of 234 Clausena anisata, 289 Vepris lanceolata and 231 Zanthoxylum capense specimens were assessed for the presence of Liberibacter by making use of a Liberibacter generic real-time PCR assay. Positive samples were further characterized by using a multi-gene phylgenetic approach based on the nucleotide sequences for the 16S, rplJ and omp genes, which respectively encode the 16S ribosomal RNA (rRNA) subunit, 50S ribosomal subunit protein L10 and the outer membrane protein. The tree host species from which Liberibacter sequences were obtained were DNA barcoded using standard procedures. Of the trees tested, 33 Cl. anisata, 17 V. lanceolata, 9 Z. capense and 1 Zanthoxylum davyi, tested positive for Liberibacter. Phylogenetic analysis of the rplJ and omp gene regions, revealed unique Liberibacter clusters associated with each tree species. Phylogenetic analysis of 16S data indicated that the strains detected in V. lanceolata and Cl. anisata were grouped with LafC, while those from Zanthoxylum species grouped separately. The presence of these bacteria in indigenous Rutaceous species should be further investigated to determine whether they are capable of being transmitted to and causing disease on commercial citrus species. To address the second aim of the study, seeds of Ca. capense were collected from two mother trees with known LafC infection. Following total DNA extraction from the midribs of leafs grown from these seeds, a LafC directed real-time PCR system was used to detect the bacterium. However, none of the samples had Ct values <35, the positive/negative threshold. From this study, no indication of seed-transmission was obtained within the limited number of samples which could be tested. The lack of vertical transmission of both Laf and LafC is seeminly a characteristic shared amongst African Liberibacter species. en_US
dc.description.availability unrestricted en_US
dc.description.department Microbiology and Plant Pathology en_US
dc.description.librarian gm2014 en_US
dc.identifier.citation Viljoen, R 2013, ‘Candidatus Liberibacter’ in four indigenous Rutaceous species from South Africa, MSc dissertation, University of Pretoria, Pretoria, viewed yymmdd <http://hdl.handle.net/2263/41009> en_US
dc.identifier.other E14/4/318/gm en_US
dc.identifier.uri http://hdl.handle.net/2263/41009
dc.language.iso en en_US
dc.publisher University of Pretoria en_ZA
dc.rights © 2013 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. en_US
dc.subject African Liberibacter species en_US
dc.subject Greening disease en_US
dc.subject South Africa en_US
dc.subject Candidatus Liberibacter africanus’ (Laf) en_US
dc.subject Indigenous rutaceous species en_US
dc.subject UCTD en_US
dc.title ‘Candidatus Liberibacter’ in four indigenous Rutaceous species from South Africa en_US
dc.type Dissertation en_US


Files in this item

This item appears in the following Collection(s)

Show simple item record