Improving wheat grain yield by employing an integrated biotechnology approach

Rhoda, Rayganah (2018-03)

Thesis (MSc)--Stellenbosch University, 2018.

Thesis

ENGLISH ABSTRACT: Wheat is a widely cultivated crop as it forms a significant part of the world’s diet, especially within developing countries. However, food insecurity is increasing at a rapid rate and to meet this demand, wheat yields need to increase by 50%, by the year 2050. To gain higher wheat yields, breeding efficiency needs to increase which can be done through employing biotechnological approaches that can aid in achieving increased yields. Yield, however, is quantitatively inherited and strongly influenced by the genotype x environment interaction. Therefore, yield-determining traits that have less genotype x environment interaction should be investigated to identify underlying inheritance of high yield, along with good husbandry practises that can result in increased wheat yield. The aim of this study was to assess high-yielding genotypes through validating yielddetermining traits using genotypic and phenotypic screening as well as the use of these highyielding genotypes as male crossing parents within the male-sterility marker-assisted mediated recurrent selection breeding (MS-MARS) scheme for the improvement of grain yield. The yield-determining traits as well as molecular markers associated to some of the yielddetermining traits were identified through literature. The molecular markers were validated through genotypic screening and each yield-determining trait was phenotypically screened for each genotype and statistically analysed. The validation of two mobile applications, SeedCounter and 1KK, that measures grain morphology was also executed. All molecular markers were validated as reliable diagnostic markers to be used in markerassisted selection (MAS) for identifying its specific yield-determining trait, except for one marker. The statistical analysis for the yield-determining traits displayed that three genotypes were better performing among this set of genotypes and therefore can be used as the male crossing parents within the next MS-MARS cycle. The association of the molecular marker with the yield-determining traits displayed negative correlations that suggests that the function of the high-yielding genes are different within this set of genotypes. Only the SeedCounter application was validated to be used as a future phenotyping tool for grain morphology and the MS-MARS cycles were successfully executed. Future studies should include the validation of more mobile applications, the identification of the relationship between yield and these molecular markers identified and QTL mapping to contribute to the understanding of the underlying genetic control of the desired phenotypes that contribute to higher grain yield.

AFRIKAANSE OPSOMMING: Koring is 'n wyd verboude gewas aangesien dit 'n belangrike deel van die wêreld se dieёt vorm, veral in ontwikkelende lande. Voedselonserkheid verhoog egter teen 'n vernuelde tempo en daarom moet die opbrengs van koring met 50%, teen die jaar 2050 verhoog. Om hoër koringopbrengste te behaal moet die effektiwiteit van die teling toeneem. Dit kan beruik word deur die gebruik van biotegnologiese tegnieke. Opbrengs is egter ‘n kwantitatief oorgeërfde eienskap en word beduidend beïnvloed deur genotipe x omgewing-interaksie. Daarom moet opbrengsbepalende eienskappe wat minder beïnvloed genotipe x omgewing-interaksie, ondersoek word om eienskappe te identifiseer, tesame met goeie verbouingspraktyke wat tot verhoogde koringopbrengste kan lei. Die doel van hierdie studie was om hoë opbrengs genotipes te evalueer deur opbrengsbepalende eienskappe te identifiseer deur gebruik te maak van genotipiese en fenotipiese sifting sowel as die gebruik van hierdie hoë opbrengs genotipes as manlike kruisingsouers binne die manlik steriliteits merker bemiddelde herhalende seleksie MS-MBHS-telingsskema vir die verbetering van graanopbrengs. Die opbrengsbepalende eienskappe sowel as molekulêre merkers wat geassosieer word met sommige van die opbrengsbepalende eienskappe is deur middel van literatuur geïdentifiseer. Die molekulêre merkers is deur genotipiese sifting bevestig en elke opbrengsbepalende eienskap is fenotipies gesif vir elke genotipe en is statisties ontleed. Die bevesting van twee mobiele toepassings, “SeedCounter” en “1KK” wat korrelmorfologie meet, is ook uitgevoer. Alle molekulêre merkers is as betroubare diagnostiese merkers bevestig om in merkerbemiddelde seleksie (MBS) gebruik te word om spesifieke opbrengsbepalende eienskap te identifiseer, behalwe vir een merker. Die statistiese analise vir die opbrengsbepalende eienskappe het getoon dat drie genotipes beter presteer as die ander en dus as die manlike kruisingsouers binne die volgende MS-MBHS- telingskema gebruik kan word. Die assosiasie van die molekulêre merker met die opbrengsbepalende eienskappe het negatiewe korrelasies vertoon wat daarop dui dat die funksie van die hoë opbrengs gene verskil in hierdie stel genotipes. Daar is bevestig dat slegs die SeedCounter-toepassing geskik is om as 'n toekomstige fenotiperingstoepassing vir korrelmorfologie gebruik te kan word en die MSMBHS siklusse was suksesvol uitgevoer. Toekomstige studies moet die bevestiging van meer mobiele-toepassings insluit, tesame met die identifisering van die verhouding tussen opbrengs en die molekulêre merkers wat geïdentifiseer was in kombinasie met QTL-kartering moet verder ondersoek word om die begrip van die onderliggende genetiese beheer van die gewenste fenotipes wat bydra tot hoër graanopbrengs beter te verstaan.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/103508
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