GENOMIC-ASSISTED BREEDING FOR BIOFORTIFIED SPRING WHEAT (TRITICUM AESTIVUM. L)

Aichatou Djibo Waziri

doi:10.7273/000007909

Biofortified wheat targeted for low-and-middle income countries has yielded considerable economic and social success. However, most of the research effort has been undertaken at research institutions in Asia and the International Maize and Wheat Improvement Center. Thus, the mainstreaming of biofortification is essential in other major cereal producing areas, especially those that export wheat, like the U.S. Wheat grown in the U.S contributes to the diet of many people prone to micronutrient deficiency worldwide. Mainstreaming has been defined as the selection for increased essential micronutrients in all germplasm and breeding pipelines in production areas where it represents a value addition. This project aimed to initiate the development of biofortified hard red spring wheat, through genomic breeding, adapted to the Pacific Northwest of the U.S. Chapter 1 delivers a brief overview of malnutrition and agricultural interventions against it, from the beginning of the 20th century to the modern era. In chapter 2, a mapping review study was conducted to complement Quantitative Trait Loci (QTL) meta-analysis. Data from QTL mapping studies, genome-wide association studies (GWAS), and candidate gene expression studies were graphically summarized to identify key genomic regions associated with iron (Fe) or zinc (Zn) grain content. The results highlighted interesting genomic regions, not reported in previous meta-analyses, with high potential for marker-assisted selection. Chromosomes 7A and 7B harbored most of those findings. Furthermore, the popular grain protein content gene GPC-B1 on chromosome 6B, also associated with increased Zn content, mapped in a QTL cluster suggesting its usefulness in various genetic backgrounds. In chapter 3, the genetic architecture of six grain nutritional traits (Zn, Fe, calcium (Ca), copper (Cu), manganese (Mn), protein content (GPC)) and two agronomic traits (plant height (PH) and thousand kernel weight (TKW), was investigated with GWAS in a collection of elite spring wheat cultivars. The results revealed stable MTAs for all the traits, except Zn. Three pleiotropic MTAs were detected on chromosomes 1A, 5A and 6B, between Cu – Mn, Ca – PH, Cu – Zn, respectively. Furthermore, pyramiding of MTAs showed a positive linear relationship between the number of favorable alleles and the trait value. Chapter 4 tackles the use of genomic prediction models to identify the most favorable genotypes and crosses to facilitate a genomic recurrent selection approach for improved concentrations of all minerals mentioned above. In the same study, the prediction of a set trait with the best predictive ability for indirect selection was also investigated. Interestingly, grain Zn concentration alone could be used to predict all the other traits. Superior parents were selected from among the training panel for recurrent selection for improved mineral nutrition. Lastly, chapter 5 proposed a protocol for a scoping review intended to understand the various ways biofortification research is being conducted, which could help researchers develop a unanimous definition of the term. This work was foundational in increasing the concentration of mineral nutrients of North American Spring wheat.

GENOMIC-ASSISTED BREEDING FOR BIOFORTIFIED SPRING WHEAT (TRITICUM AESTIVUM. L)

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