Wheat (Triticum aestivum) is one of the most important cereal crops worldwide and cultivated in a wide range of environments. The production of wheat, based on consumption and other demands, needs to be increased to meet the annual requirements for its domesticated uses. Wheat productivity is influenced by biotic and abiotic stresses. Therefore, appropriate, efficient and environmentally friendly control measures to lessen such stresses need to be applied.
Fungal diseases of wheat, including leaf rust, stripe rust, stem rust, powdery mildew and Fusarium head blight (FHB) can cause yield losses. The diseases result in a reduction in grain yield and affect grain quality negatively. The use of resistant cultivars is an effective, economical and environmentally safe approach to lower fungicide dependence and to reduce production losses due to foliar diseases. In this study, we combined rust and FHB resistance genes and/or quantitative trait loci (QTL) and molecular marker analyses were applied using polymorphic microsatellites (simple sequence repeats, SSR).
The aim of the study was to combine five rust resistance genes (against leaf, stem and stripe rust) and five FHB resistance genes/QTL for type I and II resistance into a single wheat genotype with the aid of both marker-assisted and phenotypic selection. Molecular markers used in the study are already being used in commercial breeding programmes in South Africa. The study was divided into two phases. Phase one was aimed at combining rust resistance genes/QTL into a single genotype using parental lines AvocetYrSp, Blade, Kariega and CSLr19-149-299 and to select the best lines based on the number and combination of homozygous genes/QTL present. The genes Sr2, Sr26, Lr19, Lr34/Yr18/Sr57 and QTL QYr.sgi-2B were sourced from parental lines and combined in a double cross breeding scheme followed by several rounds of selfing. Selection was done using marker-assisted selection (MAS). The two best rust resistant lines were selected. Line S16(7.3) contained QYr.sgi-2B.1, Lr34/Yr18/Sr57 and Lr19 in a homozygous state while line S726(3.2) contained Lr34/Yr18/Sr57 and Lr19 in a homozygous and Sr26 in a heterozygous state. Phenotypic screening furthermore indicated the presence of YrSp in line S726(3.2). FHB resistance QTL for the second phase of the project were sourced from Frontana (type I resistance) and CM-82036 (type II resistance). The FHB resistant lines were crossed with the two best rust resistant lines in a double cross breeding scheme and selection was done using molecular markers. The study was conducted over a period of three years.
A total of 954 individuals of a double cross population were screened with five markers associated with rust resistance genes/QTL and five markers associated with FHB resistance QTL. The following markers were used to screen for accumulated rust resistance genes/QTL: cssfr5 (Lr34/Yr18/Sr57), Gwm148 and Gwm501 (QYr.sgi-2B.1), STSLr19130 (Lr19) and Sr26#43 (Sr26). The markers DuPw227 (3A), Barc133 (3B), Gwm156, Gwm293 and Barc197.2 (5A), Gwm133 and Gwm644 (6B) and Gwm233 (7A) were used to identify individuals containing FHB resistance QTL. The number of resistance markers in the double cross family ranged between one to nine out of the 10 tested markers. The two best lines, 116.3 and 123.1, contained all markers except the marker linked to the minor FHB QTL on chromosome 7A. All tested lines contained Lr34/Yr18/Sr57 in a homozygous state while all other markers were segregating. The best lines will be self-pollinated for use in future breeding programmes.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:ufs/oai:etd.uovs.ac.za:etd-10282014-150202 |
| Date | 28 October 2014 |
| Creators | Senoko, Katleho Joyce |
| Contributors | Prof. L Herselman |
| Publisher | University of the Free State |
| Source Sets | South African National ETD Portal |
| Language | en-uk |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.uovs.ac.za//theses/available/etd-10282014-150202/restricted/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to University Free State or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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