Characterisation of EMS mutagenic bread wheat (Triticum aestivum l.) lines to investigate their water deficit stress tolerance and adaptability

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dc.contributor.advisorBotha-Oberholster, Anna-Mariaen_ZA
dc.contributor.advisorVan der Vyver, Christellen_ZA
dc.contributor.authorKayaga, Helen Ninsiimaen_ZA
dc.contributor.otherStellenbosch University. Faculty of Agrisciences. Dept. of Genetics.en_ZA
dc.date.accessioned2023-02-26T18:39:24Z
dc.date.accessioned2023-05-18T07:01:51Z
dc.date.available2023-02-26T18:39:24Z
dc.date.available2023-05-18T07:01:51Z
dc.date.issued2023-03
dc.descriptionThesis (PhDAgric)--Stellenbosch University, 2023. en_ZA
dc.description.abstractENGLISH ABSTRACT: Wheat is a staple food for 2.5 billion people worldwide and is the second most important cereal grain grown in South Africa. Water deficit stress has adverse effects on wheat productivity in the world. This is exacerbated under current unpredictable climatic patterns due to global warming. In 2017, most of the wheat production areas in South Africa were lost to alternate crops due to prevailing drought conditions. This created a need to develop water deficit stress tolerant wheat lines using ethyl methanesulfonate (EMS) because currently, no officially released varieties in the country carry such a trait. This study aimed to characterise newly developed mutagenic water stress-resilient bread wheat lines. The agro-morphological traits of three wild types and ten M3 lines were determined based on wheat descriptors in a randomised experiment with three replicates in a greenhouse. The chemical properties of flour were measured using the Inframatic 9500 NIR Grain Analyser machine, and the sedimentation tests of flour were quantified using the AACC International Method 56-60.02. The M3 lines were screened for tolerance to water deficit stress in a split-plot (3x5 factorial) experimental design that induced stress at the following growth stages: stress at seedling growth (emergence), tillering (forty days after planting), anthesis (flowering), milk development stage (seed set), and control (well-watered), and 13 subplots (bread wheat lines). Results from the analysis indicated a variation in the agro- morphological traits (18 traits) of mutants from the wild types (WTs) aside from ten traits that were similar across all bread wheat lines. Baking quality analysis showed that mutant Big 8.3 had the most desirable moisture content percentage of flour, a high protein, and wet gluten. Hence its dough has good elasticity and extensibility. The mutants performed better than WTs under water deficit stress. Big 395.1 was the most tolerant at emergence and forty days after planting, while Big 8.1 and Big 8.3 were most tolerant to water deficit stress at flowering and seed set, respectively. Previously identified drought-related genes, Sal1 (an inositol polyphosphate 1- phosphatase encoding gene) and Era1 (enhanced response to Abscisic acid 1), were analysed for single nucleotide polymorphism (SNPs) variants induced by chemical mutagenesis through sequencing complementary DNA (cDNA) of the genes and aligning them to the reference wheat genome of “Chinese Spring” available on the National Centre for Biotechnology Information (NCBI) web-based platform. I could not attain results from the Era1 sequences, and alignment results showed no differences between the Sal1 sequences of the mutant lines to that of reference genome “Chinese Spring”. In conclusion, chemical mutagenesis increased the genetic diversity of the parental bread wheat lines through induction of point mutations resulting in desirable new mutant lines like Big 8.3 with a desirable agrotype, baking quality characteristics, and high tolerance to water deficit stress at seed set.en_ZA
dc.description.abstractAFRIKAANSE OPSOMMING: Koring is 'n stapelvoedsel vir 2.5 miljard mense wêreldwyd en is die tweede belangrikste graangewas wat in Suid-Afrika verbou word. Watertekortstres het 'n nadelige uitwerking op koringproduktiwiteit in Suid-Afrika. Dit word vererger onder die huidige onvoorspelbare klimaatpatrone as gevolg van aardverwarming. Die meeste koringproduksiegebiede in Suid-Afrika het in 2017 weens alternatiewe gewasse weens die verlengde droogte toestande verlore gegaan. Dit het 'n behoefte laat ontstaan om stresverdraagsame koringlyne wat watertekorte kan oorleef, te ontwikkel. Dit is gedoen met behulp van etielmetaansulfonaat (EMS), aangesien daar tans geen amptelik vrygestelde variëteite in die land beskikbaar is wat so 'n eienskap dra nie. Hierdie studie was daarop gemik om nuut ontwikkelde mutant waterstres-weerstand verdaagsame broodkoringlyne se kenmerkte te bepaal. Die agro-morfologiese eienskappe van drie wilde tipes (WTs) en tien mutante M3-lyne is op grond van koringbeskrywers in 'n gerandomiseerde eksperiment met drie herhalings in 'n kweekhuis bepaal. Die chemiese eienskappe van meel is met die Inframatic 9500 NIR Graan Analyser-masjien gemeet, en die sedimentasietoetse van meel is volgens die AACC International Method 56-60.02-metode gekwantifiseer. Die M3-lyne is vir verdraagsaamheid teenoor watertekortstres getoets met behulp van 'n 5 x 13 faktoriese ontwerp met vyf behandelings wat bestaan het uit die kontrole (geen tekort aan water nie), en dan watertekortstres wat veroorsaak word in die volgende groeistadia, naamlik: spanning by saailing groei (emergence), bewerking (forty days after planting), antese (flowering), en die melkontwikkelingstadium (saadrang). Resultate van die studie dui op 'n variasie in die agro-morfologiese eienskappe van die mutante wanneer hulle met die wilde tipes (WTs) vergelyk word, afgesien van tien eienskappe wat oor alle broodkoringlyne ooreenstem. Uit die ontleding van bakkwaliteit is getoon dat die mutant Big 8.3 die mees gewenste voginhoud persentasie in meel, 'n hoë proteïen- en nat gluteninhoud het, en daarom het dit goeie deeg elastisiteit en rekbaarheid. Die mutante het beter gevaar as die WTs gedurende geïnduseerde watertekortstres, Big 395.1 was die mees verdraagsaam by emergence en forty days after planting, terwyl Big 8.1 en Big 8.3 die meeste verdraagsaam was teen watertekortstres by flowering en seed set, onderskeidelik. Voorheen geïdentifiseerde droogteverwante gene, Sal1 ('n inositol polifosfaat 1-fosfatase-koderende geen) en Era1 (verbeterde reaksie op Absisiensuur 1) is ook vir enkel-nukleotied polimorfisme (SNP)-variante ontleed wat veroorsaak is deur chemiese mutagenese deur die volgordes van komplementêre DNA (cDNA) van die gene te bepaal, en hulle in lyn te bring met die verwysingskoringgenoom van 'Chinese Spring' wat op die webgebaseerde platform van die National Center for Biotechnology Information (NCBI) beskikbaar is. Ek kon nie resultate vir die Era1- volgordes verkrei nie, terwyl basisvolgorde-inlynstelling geen verskille tussen die Sal1- volgordes en die verwysingsrekord van "Chinese Spring” getoon het nie. Ten slotte kon chemiese mutagenese die genetiese diversiteit van die ouerkoringlyne deur induksie van puntmutasies verhoog, wat oorsprong gegee het tot die nuwe mutantlyne soos Big 8.3 met 'n gewenste agrotipe, eienskappe van die bakgehalte en 'n hoë verdraagsaamheid teenoor watertekortstres tydens saadvorming.af_ZA
dc.description.versionDoctoralen_ZA
dc.format.extent206 pages : illustrations (some color)en_ZA
dc.identifier.urihttp://hdl.handle.net/10019.1/127050
dc.language.isoen_ZAen_ZA
dc.publisherStellenbosch : Stellenbosch Universityen_ZA
dc.rights.holderStellenbosch Universityen_ZA
dc.subject.lcshWheat (Triticum aestivum l.) -- South Africaen_ZA
dc.subject.lcshEthyl methanesulfonateen_ZA
dc.subject.lcshWheat -- Breeding -- Genetic engineeringen_ZA
dc.subject.lcshWheat -- Effect of stress onen_ZA
dc.subject.lcshBread wheat -- Effect of drought onen_ZA
dc.subject.lcshMutation breedingen_ZA
dc.subject.lcshWheat -- Drought toleranceen_ZA
dc.subject.nameUCTDen_ZA
dc.titleCharacterisation of EMS mutagenic bread wheat (Triticum aestivum l.) lines to investigate their water deficit stress tolerance and adaptabilityen_ZA
dc.typeThesisen_ZA
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