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Elucidation of drought tolerance mechanisms in South African Sorghum bicolor (L.) Moench landraces
Thesis (PhD (Biotechnology))--University of Pretoria, 2017.
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| Format: | Thesis |
| Language: | English |
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2026
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| _version_ | 1867613527387144192 |
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| access_status_str | Open Access |
| author2 | Crampton, BG |
| author_browse | Crampton, BG |
| author_facet | Crampton, BG |
| collection | Thesis |
| description | Thesis (PhD (Biotechnology))--University of Pretoria, 2017. |
| format | Thesis |
| id | oai:repository.up.ac.za:2263/110038 |
| institution | University of Pretoria (South Africa) |
| language | English |
| last_indexed | 2026-06-10T12:37:34.018Z |
| license_str | Not specified — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from UPSpace — University of Pretoria Institutional Repository |
| publishDate | 2026 |
| publishDateRange | 2026 |
| publishDateSort | 2026 |
| record_format | dspace |
| source_str | UPSpace — University of Pretoria Institutional Repository |
| spelling | oai:repository.up.ac.za:2263/110038 Elucidation of drought tolerance mechanisms in South African Sorghum bicolor (L.) Moench landraces Crampton, BG natrisha.devnarain@gmail.com O'Kennedy, M.M. Becker, JVW. Devnarain, Natrisha Sorghum Transcriptomics Landrace Drought tolerance Thesis (PhD (Biotechnology))--University of Pretoria, 2017. Drought continues to negatively impact agricultural productivity worldwide. A better understanding of important mechanisms that contribute to drought tolerance is essential to advance crop improvement initiatives. In this study, Sorghum bicolor (L.) Moench landraces were investigated as they are highly drought tolerant and adapted to the local climate of South Africa (RSA). In a preliminary seedling water deficit stress experiment, 14 landraces were screened together with a drought tolerant (P898012) and sensitive (ICSV112) genotype. Four selected landraces (LR5, LR6, LR35 and LR36) maintained higher absolute leaf water content (% LWC) than P898012, and consequently formed the basis for this study in which physiological, transcriptomic and metabolic investigations were conducted to identify potential mechanisms that underpin drought tolerance in sorghum. Physiological responses of the four landraces and P898012 were evaluated during progressive water deficit and after re-watering at growth stage II. Three treatments were imposed on plants with well-watered controls: mild (MS; four days) and severe (SS; six days) water deficit treatments, and a re-watered (RW) treatment during which plants were harvested 5 h after re-watering on day seven stress. Various physiological parameters (plant height profiles, % LWC, chlorophyll, carotenoid and proline contents) were measured and/or quantified. All five genotypes maintained % LWC comparably to controls and above 80% during MS and SS. For LR36 and LR35 at RW, % LWC was recorded within eight percent less in comparison to their controls, and proline content increased by 14- and 16-fold, respectively. All landraces maintained chlorophyll and carotenoid contents comparably with controls. During SS, significantly higher chlorophyll and carotenoid contents were recorded in LR6 and LR35 in comparison to the drought tolerant P898012. Transcriptomic analysis of leaf tissue from three selected landraces (LR5, LR6 and LR35) was conducted using sorghum cDNA microarrays comprising 35 899 transcript probes. Across the three landraces, significant differential expression of 1 797 genes, including 264 genes with currently unknown functions, were altered in response to water stress and rewatering. The modulated sorghum genes were associated with growth, regulation and protection. In LR6 during SS, Gene Ontology (GO) analysis identified significant enrichment of 26 genes involved in the „response to abiotic stimulus_ category. Quantitative RT-PCR validated the expression of a UNIVERSAL STRESS PROTEIN gene which responded to water stress and re-watering in all three landraces, and two genes associated with _-alanine betaine biosynthesis which responded to water deficit and re-watering in LR5 and LR6. Metabolite profiling of LR6 leaf extracts was conducted using 1H-NMR spectroscopy. The relative abundance of seven metabolites (alanine, glutamate, isoleucine, leucine, threonine, valine and iii _-alanine betaine) was significantly increased during severe stress in comparison to the wellwatered control. Importantly, 1H-NMR detection of _-alanine betaine supported the transcriptomic and quantitative RT-PCR findings for LR6. In conclusion, various mechanisms that contribute to drought tolerance at the physiological, transcriptomic and metabolic levels were identified in previously uncharacterised RSA sorghum landraces. Plant and Soil Sciences PhD (Biotechnology) 2026-05-15T17:26:08Z 2026-05-15T17:26:08Z 18/07/13 2017 Thesis http://hdl.handle.net/2263/110038 en application/pdf |
| spellingShingle | Sorghum Transcriptomics Landrace Drought tolerance Elucidation of drought tolerance mechanisms in South African Sorghum bicolor (L.) Moench landraces |
| title | Elucidation of drought tolerance mechanisms in South African Sorghum bicolor (L.) Moench landraces |
| title_full | Elucidation of drought tolerance mechanisms in South African Sorghum bicolor (L.) Moench landraces |
| title_fullStr | Elucidation of drought tolerance mechanisms in South African Sorghum bicolor (L.) Moench landraces |
| title_full_unstemmed | Elucidation of drought tolerance mechanisms in South African Sorghum bicolor (L.) Moench landraces |
| title_short | Elucidation of drought tolerance mechanisms in South African Sorghum bicolor (L.) Moench landraces |
| title_sort | elucidation of drought tolerance mechanisms in south african sorghum bicolor l moench landraces |
| topic | Sorghum Transcriptomics Landrace Drought tolerance |
| url | http://hdl.handle.net/2263/110038 |