• Organism

Wheat

Common wheat is a grass grown by farmers for the cereal grain, which is used as the source of flour, breads, livestock feed and alcoholic fermentation.

Overview.

Growing area: 220.4 million hectares (2014)

Scientific name: Triticum aestivum (common/bread wheat)

Average height: 0.8 - 1.2m

Habitat: Native to the Mediterranean region and southwest Asia, now grown worldwide in temperate regions

Wheat refers to the Triticum genus of grass which contains many species of wheat, the most commonly cultivated one being common wheat (Triticum aestivum), which can be further divided into cultivars. These are plant varieties that have been produced in cultivation via selective breeding. Wheat is grown for its cereal grain which is a staple of human food, being a vital source of carbohydrates and the leading vegetal protein source of the world. It is the second most-produced cereal in the world with an estimated yearly production of 750 million tons, which is predicted to increase throughout the 21st century. Wheat is a polyploidy plant, containing more than two sets of chromosomes; most eukaryotes are diploid and contain two sets of chromosomes (including humans) but most wheat species can be tetraploid (4 sets of chromosomes), or hexaploid (6 sets of chromosomes). For example, common wheat (Triticum aestivum) is hexaploid.

Common wheat is traced to the Fertile Crescent from over 10,000 years ago and gradually developed into its modern form, which is a mix of Inkorn wheat (Triticum urartu), Aegilops speltoides (an edible grass) and Aegilops tauschii (a goat grass species). Farmers would artificially select ‘mutant’ strains with desirable traits, and over time wheat developed distinct characteristics from its wild grass ancestors. These traits include larger seed grains and a tougher rachis which is hard to shatter, thus preventing seed dispersal. Specific wheat species would have undergone further evolution via artificial selection into different varieties, as farmers in different regions would select for wheat characteristics best suited to their region. Another key change occurred in the mid 20th century during the Green Revolution called dwarfing. This meant growing wheat with shorter stems, which prevented lodging - the collapse of the stem from it growing too high. Therefore, chemical fertiliser could be utilised to grow more grain and increase yield.

The range of modern wheat cultivation.

Modern wheat cultivation range map

Scientific significance.

As previously mentioned, wheat is a staple crop in many diets around the world with production having been tripled in the last 60 years and projected to increase further by the middle of the 21st century. As the human population grows in the century to an estimated 10 billion people, wheat will be key to our planet’s food security.

Though great success has been enjoyed in increasing yield since the Green Revolution in the 1960s, the rate of yield increase has been in decline since the 1990s. For governments to be able to deliver food security, it is necessary that yields continue to increase, and tackling the complex issues that will hamper this. Alongside an increase in demand due to population growth and social mobility, global climate change, limitations in available land/water/nutrients and rising energy costs raises new barriers in producing sufficient wheat to feed everyone. By improving our understanding of wheat (through sequencing its genome), new venues to both improve crop growth/yield and to grow more effectively in a rapidly changing climate will be opened. This information will become indispensable for our future food security. 

Hundreds of millions of people depend on healthy wheat crops.

Harvesting wheat

Threats.

A major threat towards wheat crops is stem rust. The Puccinia graminas fungus is the causative agent and has a complex life cycle that requires 2 hosts, and has a sexual and asexual component. Past stem rust outbreaks have devastated farmers’ wheat crops, destroying over 20% of the US’ wheat crop in several epidemics between 1917 and 1935, and crops in North Africa, Middle East and West-South Asia remain vulnerable towards future epidemics due to new pathogenic strains.

A similar pathogen threat is wheat leaf rust. There are 3 funguses of the Puccinia genus which are the causative agents of wheat rust; P. triticina (black rust), P. recondita (brown rust) and P. striiformis (yellow rust). Wheat leaf rust will spread airborne in 5 different types of spores, 3 of which will attach, germinate and develop on wheat plants. The germination process begins at a temperature of 15-20°c in moist conditions, and after 14 days the infection will begin to form spores (sporulate), which is responsible for the rusty looking pustules on the leaf.

Wheat rust up close and personal.

Wheat yellow rust

What Earlham Institute is doing.

EI is working alongside the John Innes Centre (JIC), European Bioinformatics Institute (EBI) and Rothamsted Research (RRes) to unite the expertise of wheat genetics, genomics and bioinformatics and better understand protein sequence variation, global gene expression, and the systems-level analysis of biological functions of wheat. This will transform research into crop improvement. Common wheat is the central focus of this investigation, specifically the winter wheat cultivar (variety), but Zanduri wheat (Triticum timopheevii) and Triticale (a wheat/rye hybrid) are also studied. 

This project has several inter-related goals to focus on. These include: defining the complete sequence of all wheat genes [...], identifying and annotating key genome features (genes and repeats), developing cost-effective sequencing methods for multiple wheat varieties, create resources to help understand wheat gene function, create databases to exploit genomic resources for crop research/improvement and establish networks with breeders and international projects aimed at securing future wheat supplies.