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Characterization of Exserohilum turcicum isolates from South African maize production areas
Dissertation (MSc)--University of Pretoria, 2021.
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| Format: | Thesis |
| Language: | English |
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University of Pretoria
2022
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| _version_ | 1867613704342732800 |
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| access_status_str | Open Access |
| author2 | Crampton, Bridget Genevieve |
| author_browse | Crampton, Bridget Genevieve |
| author_facet | Crampton, Bridget Genevieve |
| collection | Thesis |
| dc_rights_str_mv | © 2019 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. |
| description | Dissertation (MSc)--University of Pretoria, 2021. |
| format | Thesis |
| id | oai:repository.up.ac.za:2263/87907 |
| institution | University of Pretoria (South Africa) |
| language | English |
| last_indexed | 2026-06-10T12:40:22.637Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from UPSpace — University of Pretoria Institutional Repository |
| publishDate | 2022 |
| publishDateRange | 2022 |
| publishDateSort | 2022 |
| publisher | University of Pretoria |
| publisherStr | University of Pretoria |
| record_format | dspace |
| source_str | UPSpace — University of Pretoria Institutional Repository |
| spelling | oai:repository.up.ac.za:2263/87907 Characterization of Exserohilum turcicum isolates from South African maize production areas Crampton, Bridget Genevieve bridget.crampton@up.ac.za Barnes, Irene Haasbroek, Maria Petronella UCTD Dissertation (MSc)--University of Pretoria, 2021. Northern corn leaf blight (NCLB) is a yield-limiting foliar disease that results from infection with the fungal pathogen, Exserohilum turcicum (Pass.). Maize, sorghum and related grass species such as Johnson grass and Sudan grass serve as hosts for E. turcicum. NCLB is characterized by cigar-shaped lesions that are tan to grey in colour. In severe cases, lesions coalesce to blight the entire leaf surface, thereby reducing the photosynthetic potential of affected leaves and resulting in yield losses. The biology, life cycle and infection strategy of E. turcicum has been studied. The population structure and mode of reproduction in countries such as Kenya, Uganda, Mexico, China, and various locations in the United States of America and Europe have been investigated with random amplification of polymorphic DNA, amplified fragment length polymorphism or isozymes. The majority of previous studies performed crosses with tester strains to determine the mating type of isolates. In this dissertation, robust and reproducible simple sequence repeat (SSR) markers were developed to study the population genetic structure of E. turcicum in South Africa. In addition, a mating type multiplex PCR assay was designed to easily and rapidly determine the mating types of isolates. Of the 32 SSR primers identified from the available E. turcicum genome, thirteen markers amplified regions that were polymorphic between E. turcicum isolates from maize collected from regions within the Free State, Mpumalanga, North West, Gauteng, KwaZulu-Natal and the Northern Cape during 2005 – 2011. Screening of the markers on two isolates of sorghum collected from the Free State in 2011 revealed ten private alleles and two haplotypes unique to sorghum-infecting isolates. Three mating type PCR primers were designed from the available mating type idiomorph sequences and were successfully used in a multiplex PCR assay to determine the mating type of E. turcicum isolates. One SSR marker amplified in two isolates of E. rostratum. No amplification of E. rostratum isolates was observed with the mating type multiplex PCR assay, indicating that it may be useful to differentiate isolates of E. turcicum and E. rostratum. To study the population genetic structure of E. turcicum in South Africa, thirteen polymorphic microsatellite markers were screened on 268 E. turcicum isolates collected from maize during 2012 – 2013 from Machadodorp in Mpumalanga and four locations in the KwaZulu-Natal. The distribution of mating types was investigated among three E. turcicum populations from KwaZulu-Natal. Isolates collected from South Africa during 2012 – 2013 were grouped into three clusters based on STRUCTURE analyses, with isolates from different locations clustering together. The three groups may have resulted from multiple introductions of the E. turcicum into South Africa from other countries where it occurs. Gene and genotypic diversity was high in all populations analysed, suggesting sexual recombination events may occur among isolates from South Africa. Shared haplotypes were detected between isolates from different years and locations, although private alleles were also detected in isolates from each location. Mating type distributions revealed evidence for sexual recombination in one population from KwaZulu-Natal. The markers developed in this study will be useful in future global population genetic studies. Firstly, I would like to thank the funding bodies that made this project and my studies a reality: The National Research Foundation of South Africa (grant specific unique reference number (UID) 850760), the Maize Trust, and the University of Pretoria’s Research and Development Programme provided the financial supported needed to complete this project, The Genomics Research Institute provided me with a personal bursary in 2012, and the National research Foundation awarded me an Innovation Master’s Scholarship in 2013, which enabled my full-time studies. Secondly, I would like to extend my sincerest thanks to the people who have made this dissertation possible: Prof. Paulette Bloomer, Dr. Thierry Hoareau and Ms. Kerry Reid, for providing invaluable insight into STRUCTURE results before it was too late, Renate Zipfel and Gladys Shabangu, for patience and help in optimizing Genescan® runs and analysing results, Prof. Dave Berger, for asking the difficult questions, Members of the Molecular Plant-Pathogen Interactions (MPPI) Group and Cereal Foliar Pathogen Group (CFPG), for friendship, Dr. Maryke Craven, for providing the fungal cultures to start with, continual support throughout and who initiated this project, Dr. Irene Barnes, for helping to answer the difficult questions, providing immeasurable help in data analysis and whose work ethic and passion has been an inspiration, Dr. Bridget Crampton, for all the help in troubleshooting, valuable feedback which made chapters out of drafts, and for all the support during this project, Charl and Linda Human, who have made me a part of their family, the dinners and companionship were always excellent and greatly appreciated, My parents, Deon and Tinka Haasbroek, whose love and support has made all of my studies a possibility, thank you for all the opportunities and your unwavering belief in me, you have always been my greatest fans, Lastly, to Dirk, for making me feel loved, cherished and happy, you kept me going through difficult and trying times. I love you. Plant Science MSc Unrestricted 2022-10-24T08:54:49Z 2022-10-24T08:54:49Z 2014 2014-07 Dissertation * M14/9/165 https://repository.up.ac.za/handle/2263/87907 en © 2019 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. application/pdf application/pdf application/pdf application/pdf application/pdf application/pdf University of Pretoria |
| spellingShingle | UCTD Characterization of Exserohilum turcicum isolates from South African maize production areas |
| title | Characterization of Exserohilum turcicum isolates from South African maize production areas |
| title_full | Characterization of Exserohilum turcicum isolates from South African maize production areas |
| title_fullStr | Characterization of Exserohilum turcicum isolates from South African maize production areas |
| title_full_unstemmed | Characterization of Exserohilum turcicum isolates from South African maize production areas |
| title_short | Characterization of Exserohilum turcicum isolates from South African maize production areas |
| title_sort | characterization of exserohilum turcicum isolates from south african maize production areas |
| topic | UCTD |
| url | https://repository.up.ac.za/handle/2263/87907 |