Modelling predicts that heat stress and not drought will limit wheat yield in Europe

Global warming is characterised by shifts in weather patterns and increases in extreme weather events. New crop cultivars with specific physiological traits will therefore be required if climate change is not to result in losses of yield and food shortages. However, the intrinsic uncertainty of climate change predictions poses a challenge to plant breeders and crop scientists who have limited time and resources and must select the most appropriate traits for improvement. Modelling is, therefore, a powerful tool to identify future threats to crop production and hence targets for improvement. Wheat is the most important crop in temperate zones, including Europe, and is the staple food crop for many millions of humans and their livestock. However, its production is highly sensitive to environmental conditions, with increased temperature and incidence of drought associated with global warming posing potential threats to yield in Europe. We have therefore predicted the future impacts of these environmental changes on wheat yields using a wheat simulation model combined with climate scenarios based on fifteen global climate models from the IPCC AR4 multi-model ensemble. Despite the lower summer precipitation predicted for Europe, the impact of drought on wheat yields is likely to be smaller than at present, because the warmer conditions will result in earlier maturation before drought becomes severe later in the summer. By contrast, the probability of heat stress around flowering is predicted to increase significantly which is likely to result in considerable yield losses for heat sensitive wheat cultivars commonly grown in north Europe. Breeding strategies should therefore focus on the development of wheat varieties which are tolerant to high temperature around flowering, rather than on developing varieties resistant to drought which may be required for other parts of the world

Kafirin structure and functionality

The structural and functional properties of kafirins are reviewed. Three classes of kafirin: the a, ß and ? forms have been identified at the protein level and one, the d, has been identified only at the gene and transcript levels. All forms show high homology with the equivalent zein proteins. By analogy with the zeins it is believed that the a-kafirins probably have an extended hairpin structure in solution, comprising elements of a-helix, ß-sheet and turns folded back on itself. Kafirins are the most hydrophobic of the prolamins as shown by their solubility, and calculated hydration free energies. The proteins exhibit extensive cross-linking by disulphide bonds and on cooking form indigestible aggregates which are not solubilised by reduction of disulphide bonds. In spite of continuing studies, the reasons for the low digestibility of the protein remain uncertain and there may be several factors involved. Other research has shown that kafirins may have non-food uses and may be used to form films

Wheat glutenin subunits and dough elasticity: findings of the EUROWHEAT project

Detailed studies of wheat glutenin subunits have provided novel details of their molecular structures and interactions which allow the development of a model to explain their role in determining the visco-elastic properties of gluten and dough. The construction and analysis of near-isogenic and transgenic lines expressing novel subunit combinations or increased amounts of specific subunits allows differences in gluten properties to be related to the structures and properties of individual subunits, with potential benefits for the production of cultivars with improved properties for food processing or novel end user

Wheat grain proteins: past, present, and future

Research on wheat grain proteins is reviewed, including achievements over the past century and priorities for future research. The focus is on three groups of proteins that have major impacts on wheat quality and utilization: the gluten proteins which determine dough viscoelasticity but also trigger celiac disease in susceptible individuals, the puroindolines which are major determinants of grain texture and the amylase/ trypsin inhibitors which are food and respiratory allergens and are implicated in triggering celiac disease and nonceliac wheat sensitivity

Do ancient types of wheat have health benefits compared with modern bread wheat?

A number of studies have suggested that ancient wheats have health benefits compared with modern bread wheat. However, the mechanisms are unclear and limited numbers of genotypes have been studied, with a particular focus on Kamut (Khorasan wheat). This is important because published analyses have shown wide variation in composition between genotypes, with further effects of growth conditions. The present article therefore critically reviews published comparisons of the health benefits of ancient and modern wheats, in relation to the selection and growth of the lines, including dietary interventions and comparisons of adverse effects (allergy, intolerance, sensitivity). It is concluded that further studies are urgently required, particularly from a wider range of research groups, but also on a wider range of genotypes of ancient and modern wheat species. Furthermore, although most published studies have made efforts to ensure the comparability of material in terms of growth conditions and processing, it is essential that these are standardised in future studies and this should perhaps be a condition of publication

Can we increase the use of wheat and other cereals as sources of protein?

Wheat and other cereals are important sources of dietary protein and have the potential for exploitation to replace products based on animal proteins. However, grain protein contents are low, about 10–15%, compared to more protein-rich legumes and oilseeds. Grain protein content is determined by genetic and environmental factors, particularly nitrogen fertilisation, and is also inversely correlated with grain yield. Strategies to increase grain protein content are reviewed including exploiting genetic variation in the relationship between yield and protein content (grain protein deviation). The functional properties of cereal grains for processing are determined by the properties of the prolamin storage proteins, which include the gluten proteins of wheat. Understanding the structures and functional properties of these proteins will therefore facilitate their modification to generate a wider range of properties to extend the use of cereal proteins to replace animal proteins in food systems

The Contribution of Wheat to Human Nutrition and Health

Wheat provides 20% of calories globally but up to 50% in some regions. In addition to energy, it provides protein, dietary fibre, mineral micronutrients (iron, zinc and selenium), B vitamins and beneficial phytochemicals. However, grain composition varies between genotypes with strong effects of environment. In addition, beneficial components are concentrated in the embryo and outer layers which form the bran on milling. Hence their concentrations are depleted in white flour

Wheat

Wheat is the dominant crop in temperate countries being used for human food and livestock feed. Its success depends partly on its adaptability and high yield potential but also on the gluten protein fraction which confers the viscoelastic properties that allow dough to be processed into bread, pasta, noodles, and other food products. Wheat also contributes essential amino acids, minerals, and vitamins, and beneficial phytochemicals and dietary fibre components to the human diet, and these are particularly enriched in whole-grain products. However, wheat products are also known or suggested to be responsible for a number of adverse reactions in humans, including intolerances (notably coeliac disease) and allergies (respiratory and food). Current and future concerns include sustaining wheat production and quality with reduced inputs of agrochemicals and developing lines with enhanced quality for specific end-uses, notably for biofuels and human nutrition