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Ten thousand years ago, people began cultivating wheat, after a wild grass had accidentally crossed with wild wheat to give us the ancestor of the modern variety.
A hundred years ago, a British botanist began gathering wheat cultivars from all over the world. This year, wheat yields in the UK and France have plummeted after months of exceptionally wet weather.
All these events are connected, as crop researchers race to capitalise on wheat’s past to ensure that it has a future.
A 10,000-year success story
Evolution relies on variation and selection, and modern wheat evolved when ancestral wild wheat hybridised with Tausch’s goatgrass (Aegilops tauschii).
“Rare crossing-events around 10,000 years ago combined variation from wild goatgrass with that already present in the primitive Emmer wheats, resulting in the precursor of what we now recognise as bread wheat – allowing it to be grown across a wider geographic range than any other crop,” explains Dr Philip Howell of the NIAB (formerly the National Institute of Agricultural Botany), the UK’s largest independent crop-science research organisation.
The result was spelt wheat, the progenitor of modern varieties of bread wheat, Triticum aestivum, which now accounts for 95% of all wheat crops.
Wheat is one of three main food grains and the source of 20% of the global population’s calories. It also provides a rich source of nutrients, fibre and protein. Today, according to the US Department of Agriculture, five countries grow over 50% of the world’s wheat, with the top 20 producers accounting for about 86% of global yields.
In the past decade, however, wars and climate change have highlighted fragility. “The Ukraine war gave us an inkling of how the system could collapse,” says Dr Simon Griffiths, head of crop science at the John Innes Centre (JIC) in Norwich.
For example, in the past year, France and the UK have endured exceptionally wet weather, depressing wheat yields. Along with Ukraine, both these countries are in the top 20 wheat producers.
Although wheat has adapted to multiple regions, the areas in which it can thrive are shifting and fluctuating, and climate change brings other risks such as drought, heatwaves and increased vulnerability to pests and diseases.
Wheat is adaptable to a point, but focused breeding programmes – especially during the past 50 years – mean that plant breeders have inadvertently created specialist varieties that are vulnerable outside their ideal regions. Therefore, climate modellers worldwide have been projecting how the growing zones could shift and change.
For example, researchers in Spain found that southern regions will become inhospitable to current varieties, but in contrast, northerly regions could shift in favour of others. Climate-modelling specialists elsewhere have also noted this likely shift; for example, a longer growing season with more warmth in the UK could benefit wheat, but there are uncertainties over extreme weather events and land-use policy.
Therefore, we need new cultivars adapted to these changes, and this is where older wheat varieties and especially goatgrass show promise.
Landrace collections
A century ago, the botanist Arthur E Watkins started a collection of bread-wheat varieties, known as landraces, from over 30 countries. Landraces are locally adapted crop varieties developed by farmers through a combination of natural and managed selection.
The Watkins collection of 827 varieties is housed at the JIC and is a capacious mine of untapped genetic potential.
So far, researchers have discovered invaluable traits in these landraces that can be used in plant breeding, such as resistance to diseases and pests, improved nutritional quality, a better tolerance to heat stress and drought, and a boosted nitrogen-use efficiency. For example, a sample of experimental wheat breeds that incorporated traits from wild varieties have up to 20% more growth under heat and water stress, when compared with current varieties.
The goatgrass comeback
Goatgrass is also experiencing a resurgence. Researchers are increasingly re-examining the potential of goatgrass and the impact of hybridisations.
“We know there is much more genetic variation in collections of goatgrass than we see across the genome of modern wheat,” says Howell.
“We and other research groups are recreating those rare crossing-events using sources of goatgrass that were not captured 10,000 years ago, and crossing these ‘resynthesised’ wheats with the best-performing modern varieties. The aim is to develop diversity-enhanced ‘pre-breeding’ lines that commercial wheat breeders can use in their own breeding work, ultimately leading to future varieties.”
Howell is optimistic about this work. “Goatgrass has grown in the wild for millions of years in some very harsh environments and should be a rich source of novel diversity for improving the climate resilience of wheat,” he says. “Colleagues at CIMMYT (the world centre for wheat and maize improvement) have shown that such diversity-enhanced wheat can exhibit important traits such as tolerance to heat and drought, and often find that this maps directly back to the novel goatgrass variants that they have bred into modern wheat.”
Professor Julie King of the University of Nottingham, whose team is working with Howell and Griffiths as part of a research programme called Delivering Sustainable Wheat (DSW), says: “To date, we have probably only utilised a small fraction of the genetic variation for agronomic traits available in Aegilops tauschii.” There are also wild relatives of wheat that could provide useful genetic variation, and King’s team are working with 10 varieties.
The DSW programme combines the synergistic skills and experience of five research centres and four universities.
“Fifteen years ago, we started working closely with wheat breeders, who previously did not have sufficient access to diverse genomes,” says Griffiths. DSW and the programmes that preceded it are building on this.
Political will
Despite the number of national and international research programmes for wheat breeding, there is an absence of political urgency to fully embrace the risks to wheat and the solutions we need. “The G20 Wheat Initiative was a good start, but we need policy direction and an overarching strategy. Wheat breeders and farmers need clarity,” says Griffiths.
He hopes that policymakers will enable plant breeders to adopt the DSW’s outputs, and adds that “breeders are starting to use the traits we need. For example, there are traits that confer resistance to insects, which means less need for pesticides. This benefits biodiversity”.
“There are two big areas where we can make progress, which are more nitrogen allocation to the grain, and biological nitrification inhibition (BNI),” Griffiths says. BNI is a process that happens when crops secrete chemicals that inhibit nitrification. This is a triple-win, as it decreases nitrous oxide formation, improves grain yield through more efficient use of nitrogen, and reduces the need for fertilisers. “There are wheat landraces in the Watkins collection that have a high BNI capacity,” he adds.
Howell says: “The manufacture and application of ammonium nitrate fertiliser is by far the largest component of the carbon footprint of a loaf of bread, so reducing this requirement without compromising on yield and quality would be a fantastic step towards net-zero agriculture.”
“I would like to see wheat that requires 25% less fertiliser inputs,” says Griffiths.
The researchers have high hopes but also concerns. “The variation available in the wild relatives is such that it should be possible to transform wheat, thus making it more resilient to climate change, higher yielding and resistant to new diseases,” says King. “My one concern is that [there are] very few scientists around the world with the requisite knowledge to do this type of research. Without the funding to train new researchers and for the screening of the lines already generated, this area will be unable to fulfil its enormous potential.”
Rick Gould MIEMA is an environmental scientist and writer
