Over the past century, breeding has played a major role in improving winter wheat performance, with yields increasing from an average 5.5t/ha in 1979 to 7.8t/ha at harvest 2021.
But selecting for yield over the years has come at a cost, having indirectly reduced crop robustness, leaving wheat exposed to a range of pests, weeds and disease.
Now, faced with growing concerns about chemical resistance, mushrooming input costs and very small annual yield increases, where does this leave the future of wheat breeding?
We take a look back at the pivotal breeding moments that shaped today’s modern wheat and discover how past cultivars could help unlock a range of genetic traits to improve wheat production for the future.
A brief history
The start of the 20th century saw wheat breeding take off, with the advancement of the green revolution in the 1960s and subsequent introduction of semi-dwarf genes truly unlocking yield potential.
Straw heights fell from 1.25m to 70-80cm, redistributing dry matter from stem to grain, which saw wheat yields double.
Variety developments continued to increase wheat performance, such as the development of cultivars like Maris Huntsman (1972), which raised yields by almost 15% over rivals, and the first true semi-dwarf variety, Hobbit, in 1978.
Wheat production intensified with smaller, less-diverse rotations and increased rates of nitrogen, fungicide and growth regulators.
In fact, nitrogen use doubled in a 10-year period from the mid-1970s, where it stabilised in 1983. Yet yields continued to increase thereafter, highlighting the benefits of the improved nitrogen use efficiency offered by modern wheat varieties.
- Selection for increased yield has indirectly reduced crop robustness
- Rising resistance means growers can no longer solely rely on chemical intervention for controlling weeds, pests and disease
- Heritage wheats contain vast genetic diversity. Unlocking these traits could hold the answer to today’s wheat production issues by tailoring this to modern wheat requirements
- Gene editing and hybrid varieties could play a role in incremental yield gains and combatting chemical resistance
- Improving yields further lies in the amount of biomass a crop producers, with an optimum harvest index of 55-60%
- Industry requires a more holistic approach to wheat breeding, with smarter, more collaborative thinking
Indirect disease selection
However, the drive for greater yields didn’t come without its cost, explains independent wheat breeder and consultant Bill Angus.
Crops once controlled by robust genetic resistance became susceptible to weeds, pest and disease attack – particularly Septoria tritici.
“The introduction of the semi-dwarf genes fundamentally changed crop architecture and its genetic makeup, but the full genetic composition of these varieties, which originated in Japan, were unknown,” he says.
The semi-dwarfs Hobbit, Avalon, Norman and Longbow, closely followed by Riband and Consort, were highly susceptible to septoria.
The reduced distance between the leaves made for easy transfer of fungal inoculum via rain splash, allowing septoria to take hold.
However, the vast array of effective and available fungicides meant disease was successfully controlled.
These cultivars consequently encouraged the development of a high-input, high-output system, reliant on chemical intervention for profitable crop production.
Fast forward to today, where chemistry is less effective, does this mean varieties are no longer fit for purpose?
“It was these breeding advances that ultimately created the fight against disease. As pesticide resistance increases, we cannot just rely on chemicals.
“Finding a better balance between genetics, breeding and chemistry is necessary.”
Does heritage wheat hold the key?
Maybe it is time for breeders to retrace their steps and use the vast genetic diversity of heritage varieties to help meet the requirements of modern-day wheat production.
Unlocking the genetic potential in traditional, more robust varieties could offer greater tolerance to weeds, pests and disease attack, with reduced chemical intervention.
“Huge possibilities lie within the treasure trove of genetic diversity hidden within heritage varieties, and mining these traits, including resistance to disease, could be a huge opportunity.”
However, Mr Angus notes that this is no easy challenge, as it would require a huge push from industry. “Understanding the genetics of high-value traits would be very complex and a long-term process.
“But plant breeders have an obligation to lay down the genetic resources for the future, so it’s a possibility,” he says.
He continues that the future of increased grain potential lies in how much biomass a crop can produce, as crops need biological growth to redistribute energy into grain.
Breeding techniques such as traditional crop selection, gene editing or use of hybrid varieties could contribute to incremental gains to reach this goal.
“We need to harness a range of different technologies and explore their potential. We’ve saved millions of lives globally through the redistribution of dry matter and intensification of agriculture.
“Now comes the challenging part, where we need to ‘squeeze the pips a bit more’,” Mr Angus reports.
One way of achieving this would require the reintroduction of taller varieties that have the ability to support additional yield through greater photosynthesis rates and biomass build-up.
Currently, the wheat harvest index (the ratio of grain to total dry matter) lies at about 50%. Before the green revolution this figure was 30%.
To optimise yields further, he says breeders should be aiming for a harvest index of 55-60%.
Alternatively, genetic modification that manipulates crop characteristics by changing, deleting or inserting genes can be used to introduce desirable traits into the genome of wheat plants.
“For example, the genetic pathway of wheat crops could be modified to involve greater light inception to achieve greater levels of biomass,” he says.
Hybrid wheats also offer potential production benefits, as they consistently produce more biomass than conventional varieties.
In challenging environments, hybrids can outperform traditional varieties by 20-30% due to their more robust traits.
However, there is less appeal for their use in the UK due to our benign climate, with ample water and modest temperatures. However, their consistency on farm would be welcome as we see the climate changing, explains Mr. Angus.
“It is the adoption of the most relevant technologies and use of these tools that can bring about incremental gains to yield, disease resistance and grain quality, which will benefit overall wheat performance,” he concludes.
Breeding changes over time
Breeding techniques have changed considerably over the years, with one of the major changes being the amount of data capture and scale of varieties being tested as a result of technological advancements.
Breeders are now capable of testing thousands of new combinations each year, explains independent wheat breeder and consultant Bill Angus.
“Today’s wheat breeding is in the hands of big multinational companies, which see a large turnover of varieties.
“Thirty years ago, varieties on the Recommended List would stay there for five to 10 years, but today they only remain in the market for two to three years. This isn’t necessarily because new varieties are better than their predecessors, but perhaps they were not better in the first place, or have succumbed to new races of disease.”
Mr Angus says traditional heritage cultivars were significantly more robust, and tolerated a range of weather extremes and disease as they built up their own natural resilience over a long period of time. Modern breeding techniques that see a rapid turnover of varieties prevent this natural tolerance build-up.
He, therefore, advises industry to get back to the basic principles of breeding.
“We need a more holistic approach with greater integration throughout the whole supply chain. We need to get smarter with what we do and work together to work out the best ways forward in terms of yield, economics and crop nutrition.”