Genetic dissection of grain zinc concentration in spring wheat for mainstreaming biofortification in CIMMYT wheat breeding

Abstract

Wheat is an important staple that acts as a primary source of dietary energy, protein, and essential micronutrients such as iron (Fe) and zinc (Zn) for the world’s population. Approximately two billion people suffer from micronutrient deficiency, thus breeders have crossed high Zn progenitors such as synthetic hexaploid wheat, T. dicoccum, T. spelta, and landraces to generate wheat varieties with competitive yield and enhanced grain Zn that are being adopted by farmers in South Asia. Here we report a genome-wide association study (GWAS) using the wheat Illumina iSelect 90 K Infinitum SNP array to characterize grain Zn concentrations in 330 bread wheat lines. Grain Zn phenotype of this HarvestPlus Association Mapping (HPAM) panel was evaluated across a range of environments in India and Mexico. GWAS analysis revealed 39 marker-trait associations for grain Zn. Two larger effect QTL regions were found on chromosomes 2 and 7. Candidate genes (among them zinc finger motif of transcription-factors and metal-ion binding genes) were associated with the QTL. The linked markers and associated candidate genes identified in this study are being validated in new biparental mapping populations for marker-assisted breeding.

Assessing Genetic Diversity to Breed Competitive Biofortified Wheat With Enhanced Grain Zn and Fe Concentrations

“…The resulting advanced lines were tested at CENEB, Cd. Obregon, Mexico in an Alpha lattice design with three replications yield trial, following which the high-yielding and high Zn lines were tested in second year with six artificially manipulated environments in Obregon ranging from early-sown to late-sown (heat stress) and severe drought to moderate stress by restricted irrigation systems (Velu et al, 2016) and parallel screening in multiple sites in target countries of India and Pakistan, one of the target environments for these nutrient-enriched wheat cultivars (Velu et al, 2012, 2016, 2018). Genotypes were identified that had significantly higher grain yield and grain Zn concentration across locations.…”

Enhancing the Nutritional Quality of Major Food Crops Through Conventional and Genomics-Assisted Breeding

“…The simple reason is that most of these traits are controlled by a large number of genes having a little effect individually in the expression of these traits. In bread wheat, the major QTLs for Zn content, namely, QZn2A and QZn7B, were each having only 11.9% genetic variance ( 19 ); therefore, introgression of these QTLs with MAS into an elite background is very difficult. In addition, genotype by environment interaction increases the complexity many folds in the transfer of target traits.…”

“…In wheat, various studies have reported QTL for high grain Fe and Zn concentrations on chromosomes 1A, 1D, 1B, 2A, 2B, 3B, 3D, 4B, 5A, 6A, 6B, 7A, 7B, and 7D in hexaploid wheat ( 16 , 18 , 20 – 24 ) and on chromosome 2 in barley ( 25 ) ( Table 1 ). Recently, Velu et al ( 19 ) evaluated the HarvestPlus Association Mapping panel across a range of environments in India and Mexico. GWAS analysis revealed two larger QTL regions on chromosomes 2 and 7 for large grain Zn content.…”

Editorial: Aegilops: Promising Genesources to Improve Agronomical and Quality Traits of Wheat

“…Aegilops has attracted further attention in relation to increasing the grain mineral content of wheat. In particular, to produce biofortified wheat with higher the contents of iron and zinc in order to alleviate deficiencies in these minerals which currently affect more than 2 billion people worldwide ( Cakmak, 2017 ; Black et al, 2013 ; Velu et al, 2018b ). Some Aegilops species have been reported to contain three to four-fold higher concentrations of Zn and Fe grain content than wheat, including A. longissima (Sl), A. kotschyi (US), A. peregrina (US), A. cylindrica (CD), A. ventricosa (DN) and A. geniculata (UM) ( Rawat et al, 2009 ).…”