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Characterization of Diuraphis noxia diversity and host response
Dissertation (MSc (Genetics))--University of Pretoria, 2015.
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| Format: | Thesis |
| Language: | English |
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2026
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| _version_ | 1867613490629312512 |
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| access_status_str | Open Access |
| author2 | Botha-Oberholster, Anna-Maria |
| author_browse | Botha-Oberholster, Anna-Maria |
| author_facet | Botha-Oberholster, Anna-Maria |
| collection | Thesis |
| description | Dissertation (MSc (Genetics))--University of Pretoria, 2015. |
| format | Thesis |
| id | oai:repository.up.ac.za:2263/110170 |
| institution | University of Pretoria (South Africa) |
| language | English |
| last_indexed | 2026-06-10T12:36:58.812Z |
| 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:2263/110170 Characterization of Diuraphis noxia diversity and host response Botha-Oberholster, Anna-Maria nfvburger@sun.ac.za Venter, Eduard Burger, N. Francois V. Salivary expression Adaptive regulation Dissertation (MSc (Genetics))--University of Pretoria, 2015. Diuraphis noxia (Russian wheat aphid, Kurdjumov) (Hemiptera: Aphididae) is a phloem feeding insect pest of wheat, barley and other Bromus spp. which is responsible for millions of dollars in crop losses and control measures. Since its introduction into South Africa in late 1978, D. noxia has successfully invaded all wheat producing countries within a decade, with the exception of Australia. The adaptability of aphid effectors, illustrated by the prolific biotypification of D. noxia, has rendered most previous sources of host plant resistance unusable and is believed to be a major factor driving aphid biotypification. The study undertaken here attempted to elucidate the biotypic nature of D. noxia by first studying its spread and diversity internationally, after which salivary transcriptome data was collected for two closely related biotypes that were transferred between a wheat differential set consisting of 16 resistant and susceptible cultivars. Although it can be generally accepted that D. noxia introductions into a naive environment is facilitated through the transport of cereal grains, the reintroduction of aphids into previously colonised areas is difficult to trace, especially with the prevailing dogma insinuating that new biotypes preferentially stem from founder colonisations. Strong evidence has been provided in the current study to illustrate the continued movement of D. noxia biotypes between infested areas, by making use of conserved sequences in plasmids borne by the obligate endosymbiont B. aphidicola and available trade data for wheat. Data presented here indemnified D. noxia biotype SA1 as the initial catalyst for the global expansion of D. noxia experienced during the turn of the millennia and sowed doubt on the local biotypification of many US and South African Page | ii biotypes. Salivary expression profiles obtained from aphid heads when moved between preference and non-preference hosts has helped shed light on the modular nature of aphid saliva. It was found that the virulent D. noxia biotype SAM was able to selectively upregulate more transcripts when confronted with feeding on a naive host, than was the case with the less virulent D. noxia biotype SA1, suggesting increased genomic plasticity when coping with a stressful or changing environment. Host genotype also appears to determine the efficacy of R-genes in that the less virulent D. noxia biotype SA1 reacted more consistently to host genotype than to the R-gene it was faced with, as opposed to D. noxia SAM biotype whose regulation appeared to be temporally mediated. Collectively the observed changes corroborate earlier observations that changes in host induces significant changes in the proteome of phytophagous hemipterans. The data generated here suggests that highly specialized hemipterans possess the ability to regulate their salivary transcriptome in a realtime manner to adapt to their feeding environment, thus countering plant compounds through inducible salivary transcripts with resulting protein biosynthesis. Taken together, results from this study implicates that future conventional breeding efforts in isolated environments must contend not only with endemic D. noxia biotypes, or with others appearing as a result of continued and frequent movement of D. noxia, but also with an aphid salivary cohort that stretches the limit of adaptation Genetics MSc (Genetics) 2026-05-15T17:26:33Z 2026-05-15T17:26:33Z 15/07/14 2015 Dissertation http://hdl.handle.net/2263/110170 en application/pdf |
| spellingShingle | Salivary expression Adaptive regulation Characterization of Diuraphis noxia diversity and host response |
| title | Characterization of Diuraphis noxia diversity and host response |
| title_full | Characterization of Diuraphis noxia diversity and host response |
| title_fullStr | Characterization of Diuraphis noxia diversity and host response |
| title_full_unstemmed | Characterization of Diuraphis noxia diversity and host response |
| title_short | Characterization of Diuraphis noxia diversity and host response |
| title_sort | characterization of diuraphis noxia diversity and host response |
| topic | Salivary expression Adaptive regulation |
| url | http://hdl.handle.net/2263/110170 |