A collection of bread slices, cake and various wheat grains on a wooden surface

Wheat is a staple food for 35% of the world's population. Its global trade is the largest compared to all other crops. © National Institutes of Health/wiki

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Why you should care about scientists sequencing the wheat genome

Wheat is one of the most valuable food crops in the world, contributing about a fifth of the total calories consumed by humans every year.

Scientists are studying the genes of wheat varieties to understand how the plant has changed throughout history. It could help reduce agricultural pressures on the planet, and ultimately protect food security for future generations.

As a highly nutritious plant, wheat is one of the world's oldest and most important crops. Together with rice and corn, wheat feeds the world.

Humans have been changing wheat plants since the birth of farming. For thousands of years, farmers would take seeds from the biggest and strongest plants and grow them, improving the quality of crops over time. This is known as selective breeding.

Advances in technology in the eighteenth and nineteenth centuries allowed farmers to produce more crops than ever, but it was only in the early twentieth century when people started understanding genetics that modern farming changed in a big way.

Wheat was selectively bred on a global scale for high yields, greater resistance to diseases and better taste.

Dr Matthew Clark, a research leader at the Museum, is exploring how this selective breeding has changed the wheat plants we eat today. This is part of a large project in collaboration with partners around the world, including in Mexico and the UK.

'I am interested in learning about how we have selected for differences,' says Matt. 'People haven't always known as much about genetics as we do now. I think they may have inadvertently thrown away valuable information that could help us farm efficiently in a much more environmentally friendly way.'

In order to grow crops with desired traits, farmers would transfer the stamen from one variety to the flower of another before self-fertilisation took place
 

How humans have changed wheat

The wheat grown by early farmers reached over 160 centimetres, dwarfing people next to it. Its tall, willowy form allowed it to soak up sunlight and easily outcompete other plants.

However, this also meant wheat was susceptible to wind which would often knock them down and make them hard to harvest, even by hand.

The edible seeds would sometimes become damp and sprout, or get eaten by animals, so they would not make it to the human food chain.

Modern breeders started selectively growing short stemmed, disease-resistant wheat varieties, also known as semi-dwarves.

These were championed by Norman Borlaug, an American agronomist and the 1970 Nobel Peace Prize winner, who is often credited with saving a billion people from starvation.

While this has allowed the plant to withstand wind damage better and feed millions more people, it left the wheat vulnerable to competition for light.

Herbicide and fungicide were introduced into wheat farming to eliminate the competition, but this impacted the health of the soil by changing the balance of nutrients.

Farmers have long known that animal and human faeces contain a lot of nutrients that are good for plant growth, so have often used these as manure-based fertilisers.

Sea bird guano is especially rich in nitrogen and was used extensively in the nineteenth and early twentieth centuries, until they became scarce and artificial fertiliser was invented.

'Over time, we got better at cultivating crops because we changed the way we did things,' says Matt. 'We made the soil richer which allowed us to adjust what we were growing.'

But selective breeding has also resulted in the loss of genetic diversity. This means most of the wheat crops grown now are similar to each other, reducing their ability to adapt and decreasing their resilience to new diseases.

'Take somewhere like the mid-west of America where they grow fields of maize the size of UK counties,' says Matt. 'They are all genetically identical because they are grown by the same few companies, but all it takes is one pathogen to run through everything and create a massive pandemic - unless you spray with pesticides.'

This is worrying for everyone. If wheat crops were devastated by a disease, it would seriously threaten global food supplies.

So what can we do to prevent that from happening?

If two fungi from the same species meet, they mate and create fairy ring of toad stools. These fungi breaking down organic matter in the soil and return nutrients to create a healthy ecosystem. This is often by forming symbiotic relationships with plant root systems in the area, exchanging nutrients for sugars. © Henk Monster/wiki (CC BY 3.0)
 

The wheat genome was once considered too complex to sequence. That's because it is enormous - five times bigger than the human genome - and it is a hybrid of three different grass species.

But in 2018 it was finally achieved. More than 200 scientists all over the world - including Matt - contributed to the work.

Matt and colleagues have now sequenced about ten different modern wheat genomes from the UK and Europe, in addition to four that had been sequenced before.

They are now including samples from the Museum's collection in the study and will soon expand to wheat grown in other parts of the world such as South America and Asia to learn the differences.

'If you have the genome, it means you can design the markers that enable you to breed better crops,' explains Matt. 'And that might allow us to decrease the impacts of agriculture on the environment.'

It ultimately means we might be able to breed wheat that is bountiful, resistant to diseases and able to thrive in soil without artificial fertilisers.

The research is especially useful for developing countries where farmers might not be able to adopt the same industrialised approach, or organic farmers who don't want to put loads of chemicals on their produce.

'What we've achieved in farming has been incredible but there's been a cost in terms of energy use and environmental damage,' says Matt.

The overuse of fertilisers can damage plants, pollute the soil and leach into nearby rivers, upsetting the ecosystems there.

'Maybe we can reintroduce some of the things we have thrown away back into modern agriculture. It would be amazing if we could continue achieving what we have now but with less environmental impacts.'