Bread wheat (Triticum aestivum L.) is an important cereal crop that provides >20% of the global calorie intake. Bread wheat contains micronutrients, and thus plays a significant role in nutritional and food securities especially in developing countries. However, its grains are inherently deficient in some micronutrients, particularly iron and zinc, which makes them important biofortification targets. Our objective was to investigate variations in micronutrients and their relationship with grain yield components in wheat under four environments in South Africa. A population of 139 doubled haploid lines derived from a cross between cvv. Tugela-DN and Elands was phenotyped for grain iron and grain zinc concentrations and grain yield components. Heat and drought conditions at Arlington resulted in higher grain zinc concentrations and lower yield component traits; the opposite trend was observed at Bethlehem and Harrismith for both micronutrients and yield components. All traits showed transgressive segregation. Grain iron and zinc concentrations were significantly positively correlated in all four environments. The correlations between these minerals and yield components were inconsistent and ranged from significant to insignificant depending on the environment, indicating that this relationship is non-genetic. The results demonstrate that biofortification of both grain iron and grain zinc can be included as part of the breeding objectives and will not necessarily have adverse relationships with grain yield components.
Grain yield is a quantitatively inherited complex trait that is strongly influenced by interacting genetic and environmental factors. The identification of major quantitative trait loci (QTL) for plant height (PH) and yield component traits (YCT) is important for improving yield potential through wheat breeding. We performed a QTL analysis for PH and YCT in the Tugela-DN × Elands doubled haploid (DH) population using a genotype-by-sequence single nucleotide polymorphism and a silicoDArT-based genetic map. Field trials were conducted under rain-fed conditions across five environments in the Free State Province of South Africa during the 2017–2018 and 2018–2019 cropping seasons. Analysis of variance revealed significant differences (p < 0.001) among DH lines and the environments. However, for G × E interactions, significant differences (p < 0.05) were only observed for spikelet number per spike. Broad-sense heritability estimates of all traits ranged between 0.44 and 0.81. Nine QTL, viz. QPh.sgi-6A.2 and QPh.sgi-4D for PH, QSl.sgi-6A.2 and QSl.sgi-7A for spike length, QGns.sgi-3B for grain number per spike (GNS), QGwps.sgi-7B for grain weight per spike (GWPS), QGw.sgi-2A and QGw.sgi-7A for grain width, and QGl.sgi-3B for grain length (GL), were identified on chromosomes 2A, 3B, 4D, 6A, 7A, and 7B, in two or more environments. Some of these QTL exhibited pleiotropic effects. The QPh.sgi-6A.2 QTL for PH and QGwps.sgi-7B for GWPS appear to be novel QTL, while the rest of the reported QTL validated previously identified QTL for PH and YCT. The study also reported a trade-off between GL and GNS. The findings of this study will be useful in elucidating the genetic architecture of yield component traits contributing to the development of new dryland wheat varieties with high and stable yield.
Wheat (Triticum aestivum L.) houses a wide range of nutritional components such as iron (Fe), zinc (Zn), vitamins and phenolic acids, which are important for plant metabolism and human health. The bioavailability of these nutritional components is low due to their interaction with other components and low quantity in the endosperm. Biofortiication is a more sustainable approach that could improve the bioavailability of essential nutritional components. Substantial progress has been made to improve nutritional quality through the application of conventional, technological and transgenic approaches. This has led to the discovery, cloning and introgression of the Gpc-B1 gene; the invention of online databases with minimally characterized biosynthetic, metabolic pathways and biological processes of wheat-related species; the establishment of genetic variation in grain Fe and Zn content and the biofortiication of wheat with Zn by the HarvestPlus organization. Nonetheless, the biofortiication of wheat with micronutrients and phenolic acids is still a challenge due to incomplete understanding of the wheat genome, biosynthesis and translocation of selected nutritional components into diferent wheat grain compartments. There is a need to integrate selected omics technologies to obtain a holistic overview and manipulate key biological processes involved in the remobilization and biosynthesis of nutritional components into desired wheat grain compartments.
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