Plant breeding is unlikely to solve all our future woes, despite the new technologies available to the plant breeding community, says leading wheat breeder Bill Angus.
Growers will always have to rely on some form of chemical input to achieve full yield potential in wheat in the UK, Mr Angus suggests.
Over the past century plant breeding has played a major role in improving winter wheat performance. In just over three decades UK yields have doubled. In 1970 the UK mean winter wheat yield came in at 4.0 t/ha and by 2003 it was 8.0 t/ha. As a result of this leap in breeding performance and advances in cultivation and drilling technology, the UK winter wheat area doubled too. The UK went from a wheat importer to wheat exporter.
But the pace of change is unlikely to remain so high – despite huge developments in breeding science. The cracking of the wheat genome was heralded as a great success but the benefits are unlikely to be seen for some time, and may not be as ground breaking as first thought. What it has shown is just how complex the wheat plant is. Wheat is very complex and being a polyploid it has six sets of chromosomes, whereas humans have just two. “The wheat genome contains a lot of DNA, and to complicate matters it has three copies of everything. The potential to push yield potential is there but identifying specific traits will not be easy,” Mr Angus says.
It is photosynthesis that offers the best chance of improving wheat yields in the future. Options could include hybrid technology and GM, but he also feels work with related species could be an exciting opportunity. “Government funded research at the University of Nottingham, the John Innes Centre and NIAB could really open up new opportunities.”
With the recent historical gains have come downsides to balance out the benefits, the biggest being the low levels of Septoria resistance in modern varieties.
That balance can be seen from the start of the modern day plant science revolution. When the dwarfing gene arrived it changed everything and heralded a boom time for growers. By changing the balance of plant material, the emphasis shifted from redirecting stem reserves to grain, giving a substantial yield boost.
The story started just after the Second World War when short Japanese varieties were taken by the Americans who used it
for crossing. This material was to lead to the birth of the Green Revolution and the saving of millions of people from starvation. Eventually derivatives arrived in the UK and were used to develop the first dwarf wheats. But with it came a particular weakness against Septoria, and the start of where we are today.
“We’ve made the mistake of being overly focused on yield, and we are still making it today. A small pool of genetics led to
a whole succession of Septoria prone varieties putting pressure on fungicides. The first commercially successful dwarfs
such as Longbow, Norman and Avalon, were followed by Riband and Consort. At one time Riband held more than 25% of the
area. Treated fungicide results took our eye off the problem we were creating.
“Unfortunately we still see susceptible varieties being recommended today. We have a great climate for growing wheat but also Septoria too. We’re continuing to follow a flawed strategy,” he warns.
Resistance based on a number of genes (polygenic resistance) has to be the answer he believes but even then it won’t be the complete answer. “There’s no such thing as full genetic resistance (immunity) to Septoria – only degrees of resistance.
Major gene resistance does exist but is potentially dangerous – similar to the pressure which parallels the current situation in rusts. We’ve seen in the past varieties crash to yellow rust simply because a new race arrives which overcomes the major gene resistance – we don’t want to see this story repeated with Septoria. Polygenic resistance should provide protection against a range of strains or races. But even this resistance will not defeat something like Septoria - it just slows it down.”
This is why chemistry will always have a part to play. He points out that if growers want to exploit all that a variety offers, inputs are essential. “Variety resistance isn’t an opportunity to cut fungicide use, all varieties still have degrees of susceptibility. The challenge is to preserve yield potential.”
Research undertaken by Mr Angus has shown just how important inputs are to realising that potential. Fungicide trials at his Suffolk site showed big responses last season. “We applied a robust four spray programme to a range of varieties with various degrees of Septoria and rust resistance. Five varieties were rated as good for Septoria yet the average response was a 2.3 x return on investment in the spray programme, and this was a fungicide programme that would exceed the cost of those found in commercial farming. It shows just how valuable fungicides are.”
But he also wants to see more consideration to variety selection – something he acknowledges is difficult with many breeders sharing the same genetic pool. “We need to be thinking of not just resistance to specific diseases but resistance to specific races or strains. The more diversity over your wheat area the better. If we want to produce consistent yield performance that’s where we need to be in the future,” he concludes.