The grain quality of wheat wild relatives in the evolutionary context

Key message We evaluated the potential of wheat wild relatives for the improvement in grain quality characteristics including micronutrients (Fe, Zn) and gluten and identified diploid wheats and the timopheevii lineage as the most promising resources. Abstract Domestication enabled the advancement of civilization through modification of plants according to human requirements. Continuous selection and cultivation of domesticated plants induced genetic bottlenecks. However, ancient diversity has been conserved in crop wild relatives. Wheat (Triticum aestivum L.; Triticum durum Desf.) is one of the most important staple foods and was among the first domesticated crop species. Its evolutionary diversity includes diploid, tetraploid and hexaploid species from the Triticum and Aegilops taxa and different genomes, generating an AA, BBAA/GGAA and BBAADD/GGAAAmAm genepool, respectively. Breeding and improvement in wheat altered its grain quality. In this review, we identified evolutionary patterns and the potential of wheat wild relatives for quality improvement regarding the micronutrients Iron (Fe) and Zinc (Zn), the gluten storage proteins α-gliadins and high molecular weight glutenin subunits (HMW-GS), and the secondary metabolite phenolics. Generally, the timopheevii lineage has been neglected to date regarding grain quality studies. Thus, the timopheevii lineage should be subject to grain quality research to explore the full diversity of the wheat gene pool.

Harnessing the Wild Relatives and Landraces for Fe and Zn Biofortification in Wheat through Genetic Interventions—A Review

Micronutrient deficiencies, particularly iron (Fe) and zinc (Zn), in human diets are affecting over three billion people globally, especially in developing nations where diet is cereal-based. Wheat is one of several important cereal crops that provide food calories to nearly one-third of the population of the world. However, the bioavailability of Zn and Fe in wheat is inherently low, especially under Zn deficient soils. Although various fortification approaches are available, biofortification, i.e., development of mineral-enriched cultivars, is an efficient and sustainable approach to alleviate malnutrition. There is enormous variability in Fe and Zn in wheat germplasm, especially in wild relatives, but this is not utilized to the full extent. Grain Fe and Zn are quantitatively inherited, but high-heritability and genetic correlation at multiple locations indicate the high stability of Fe and Zn in wheat. In the last decade, pre-breeding activities have explored the potential of wild relatives to develop Fe and Zn rich wheat varieties. Furthermore, recent advances in molecular biology have improved the understanding of the uptake, storage, and bioavailability of Fe and Zn. Various transportation proteins encoding genes like YSL 2, IRT 1, OsNAS 3, VIT 1, and VIT 2 have been identified for Fe and Zn uptake, transfer, and accumulation at different developing stages. Hence, the availability of major genomic regions for Fe and Zn content and genome editing technologies are likely to result in high-yielding Fe and Zn biofortified wheat varieties. This review covers the importance of wheat wild relatives for Fe and Zn biofortification, progress in genomics-assisted breeding, and transgenic breeding for improving Fe and Zn content in wheat.

Genetic diversity, distribution and domestication history of the neglected GGAtAt genepool of wheat

Key message We present a comprehensive survey of cytogenetic and genomic diversity of the GGAtAt genepool of wheat, thereby unlocking these plant genetic resources for wheat improvement. Abstract Wheat yields are stagnating around the world and new sources of genes for resistance or tolerances to abiotic traits are required. In this context, the tetraploid wheat wild relatives are among the key candidates for wheat improvement. Despite its potential huge value for wheat breeding, the tetraploid GGAtAt genepool is largely neglected. Understanding the population structure, native distribution range, intraspecific variation of the entire tetraploid GGAtAt genepool and its domestication history would further its use for wheat improvement. The paper provides the first comprehensive survey of genomic and cytogenetic diversity sampling the full breadth and depth of the tetraploid GGAtAt genepool. According to the results obtained, the extant GGAtAt genepool consists of three distinct lineages. We provide detailed insights into the cytogenetic composition of GGAtAt wheats, revealed group- and population-specific markers and show that chromosomal rearrangements play an important role in intraspecific diversity of T. araraticum. The origin and domestication history of the GGAtAt lineages is discussed in the context of state-of-the-art archaeobotanical finds. We shed new light on the complex evolutionary history of the GGAtAt wheat genepool and provide the basis for an increased use of the GGAtAt wheat genepool for wheat improvement. The findings have implications for our understanding of the origins of agriculture in southwest Asia.

Characterization of Potential Candidate Genes for Grain Size in Wild Emmer Wheat Triticum Dicoccoides

There is an incessant need to address food security in staple crops, and the crop yield is positively correlated with grain weight. Grain size, determined by grain length and width, is an essential component of final grain weight in cereals. Wheat wild relatives are the goldmine to harness any trait of interest, including the component traits of grain size. It is crucial to understand the detailed mechanism of grain size formation and unravel underlying genes controlling grain size in these species for their proper utilization in wheat improvement. In this study, gene expression analysis was performed on developing grain in wild tetraploid progenitor Triticum dicoccoides (AABB) to identify candidate genes involved in determining grain size. Four T. dicoccoides accessions were selected, two (pau5228 and pau5322) with higher grain length and weight and two (pau14703 and pau14756) with comparatively smaller grains.Six genes out of the eight genes selected for expression study, viz., GL7, TaGL3, TaGS5, GS3, SRS3, and TaGASR7, were upregulated from 8 days post-anthesis (DPA) to 20 DPA in both the large grain accessions, while TaGW2 gene was upregulated in both small grain accessions. TGW6 was downregulated in all the accessions at all stages of grain development. The results indicated that the selected genes play an essential role in grain size formation by controlling individual morphometric components of grain length and width. Targeted introgression genes controlling grain size components will eventually aid in improving grains yield.

Origin of black glume color in the Triticum aestivum lines with introgressions from wheat wild relatives

ABSTRACT Dark color of a glume in Triticinae is a known morphological marker with studied genetic control. However, the pigments that provide the color development, molecular basis of their biosynthesis, and mechanisms of its regulation are still unknown. Dark color of glumes is a common trait in the Triticum aestivum lines with alien introgressions. To find out the basis of this trait, we studied nature of the compounds that color the glumes by analyzing the total phenolic content (TPC) in the dark glumed introgression lines (ILs) and comparing it to their parents. TPC in the dark ILs was found to be higher than in their parents and in the light lines. All studied genotypes were screened for the expression of eight genes encoding the flavonoid biosynthesis pathway enzymes. Expression of three flavonoid genes in the pathway were changed in the ILs compared to their parents. Firstly, the expression of F3’H and FNS was absent in the lines with introgressions from Aegilops spp. The expression of three genes, F3’H, FLS, and FNS, was found to be altered in the light lines with introgressions from A. muticum. No expression of the F3’H was detected in the T. aestivum / A. muticum lines with light and dark plants, and the other genes of the pathway were found to be expressed at the parental levels. No correlation between the expression profiles and the phenotype was found in the T. aestivum / A. muticum lines. So we hypothesized that other undetected changes are present in these lines.

Special Issue: Breeding Towards Agricultural Sustainability - Invited

Wheat yields are stagnating around the world and new sources of genes for resistance or tolerances to abiotic traits are required. In this context, the tetraploid wheat wild relatives are among the key candidates for wheat improvement. Despite of its potential huge value for wheat breeding, the tetraploid GGAtAt genepool is largely neglected. Understanding the population structure, native distribution range, intraspecific variation of the entire tetraploid GGAtAt genepool and its domestication history would further its use for wheat improvement. We report the first comprehensive survey of genomic and cytogenetic diversity sampling the full breadth and depth of the tetraploid GGAtAt genepool. We show that the extant GGAtAt genepool consists of three distinct lineages. We provide detailed insights into the cytogenetic composition of GGAtAt wheats, revealed group-, and population-specific markers and show that chromosomal rearrangements play an important role in intraspecific diversity of T. araraticum. We discuss the origin and domestication history of the GGAtAt lineages in the context of state-of-the-art archaeobotanical finds. We shed new light on the complex evolutionary history of the GGAtAt wheat genepool. We provide the basis for an increased use of the GGAtAt wheat genepool for wheat improvement. The findings have implications for our understanding of the origins of agriculture in southwest Asia.

Genetic diversity, distribution and domestication history of the neglected GGAtAt genepool of wheat

BackgroundWheat yields are stagnating around the world and new sources of genes for resistance or tolerances to abiotic traits are required. In this context, the tetraploid wheat wild relatives are among the key candidates for wheat improvement. Despite of its potential huge value for wheat breeding, the tetraploid GGAtAt genepool is largely neglected. Understanding the population structure, native distribution range, intraspecific variation of the entire tetraploid GGAtAt genepool and its domestication history would further its use for wheat improvement.ResultsWe report the first comprehensive survey of genomic and cytogenetic diversity sampling the full breadth and depth of the tetraploid GGAtAt genepool. We show that the extant GGAtAt genepool consists of three distinct lineages. We provide detailed insights into the cytogenetic composition of GGAtAt wheats, revealed group-, and population-specific markers and show that chromosomal rearrangements play an important role in intraspecific diversity of T. araraticum. We discuss the origin and domestication history of the GGAtAt lineages in the context of state-of-the-art archaeobotanical finds.ConclusionsWe shed new light on the complex evolutionary history of the GGAtAt wheat genepool. We provide the basis for an increased use of the GGAtAt wheat genepool for wheat improvement. The findings have implications for our understanding of the origins of agriculture in southwest Asia.

Molecular breeding for improving aluminium resistance in wheat.

This chapter aims at describing the main physiological mechanisms associated with aluminium (Al) resistance in wheat and how the research about these mechanisms has evolved to its current status. Practical aspects of phenotyping and using the molecular basis to increase Al resistance, which can be easily introduced in breeding programmes, are detailed. This chapter discusses the reliability of methods to screen root growth under Al stress, the allelic variation of genes associated with the main Al resistance mechanism in wheat, the quantitative trait loci and genomic regions that might contain minor Al tolerance genes, the use of wheat wild relatives, the uncertainties of developing transgenic wheat for greater Al resistance and the development of Al-resistant lines of durum wheat (Triticum turgidum subsp. durum).