A new paper from scientists at the John Innes Centre in Norwich explains why plant breeders have found it difficult to produce wheat varieties which combine high yield and good resistance to Septoria, a disease in wheat which can cut yield losses by up to 50%. It traces the problem back to decisions made nearly sixty years ago.
Septoria is the most destructive disease affecting wheat in the UK. As the fungus has become insensitive to most fungicides, demand for new Septoria resistant wheat varieties has risen sharply.
Septoria emerged as a serious threat to wheat in the 1970s. Since then, progress in breeding new varieties which combine high yield with resistance to Septoria has been slow.
Professor James Brown and his colleague Dr Lia Arraiano analysed resistance and susceptibility to Septoria in wheat varieties grown in the UK between 1860 and 2000. Using a technique called association genetics, they found that the gene with the biggest effect on increasing susceptibility to Septoria is very closely linked to one that increases yield and grain size.
Professor Brown said: "As we studied a historical set of varieties covering more than a century of wheat breeding, we discovered where the small region of the genome that increases both Septoria and yield came from. We traced it back to a variety called Heines Peko, which was used to breed for yield and rust resistance in the late 1950s."
Heines Peko was crossed with Cappelle Desprez, the major wheat variety in Britain at the time. This cross was so influential that all modern wheats bred in Britain are descended from it. Professor Brown suggests that as wheat breeders selected ever more strongly for higher yield, susceptibility to Septoria hitch-hiked along with it.
"My group is now trying to find out if the connection between the two traits can be broken" he added.
Breeders appreciate that increased yield is the main driver of the market for new varieties. Professor Brown points out that although Septoria resistance has improved in recommended varieties over the last ten years, the lack of knowledge about the relationship between yield and susceptibility to Septoria has hindered progress.
"It's surprising," he adds, "that a decision made so long ago has had such a long-lasting effect."
Ed Flatman, Head of European Wheat Breeding at Limagrain said: "Professor Brown and Dr Arraiano's work was one of the very first applications of association genetics in wheat and it has helped us to understand the past history of breeding for resistance to Septoria. We have now taken James' results and built on them by identifying novel Septoria resistances in current, high yielding elite varieties."
Dr Arraiano and Professor Brown's research points to a way of rising to the challenge of combining yield and Septoria resistance. They found ten other genes scattered throughout the genome with smaller effects on Septoria. They also found that nearly half the variation in Septoria was controlled by genes with effects that were too small to identify individually. "We know the genes are there," said Professor Brown, "but we don't know where they are."
Professor Brown is confident that breeders can make durable advances in Septoria resistance with this knowledge. "When breeders make crosses between diverse varieties, they produce new combinations of genes with small effects," he explains.
"Then if they run field trials at sites where Septoria is really rampant, they can spot the most resistant lines to commercialise and to use in the next generation of breeding."
He believes this approach will enable breeders to improve Septoria resistance, while minimising undesirable side-effects, such as reductions in yield.
Professor Brown said: "With the pressures of restrictions on pesticide use added to Septoria becoming insensitive to most fungicides, farmers need varieties which combine yield and quality with resistance to Septoria and other diseases. Our breakthrough should accelerate progress in developing these new varieties."
The research was supported by Department for Environment Food and Rural Affairs (DEFRA) through the Sustainable Arable LINK programme, with support from AHDB and a consortium of plant breeding companies: Elsoms Seeds, Limagrain, Sejet, SW Seed and Syngenta, and by the Biotechnology and Biological Sciences Research Council (BBSRC).
Notes to editors
1. The paper, 'Sources of resistance and susceptibility to Septoria tritici blotch of wheat' is published in Molecular Plant Pathology on Friday 21 October 2016. The paper was co-authored by Dr Lia Arraiano, formerly at the John Innes Centre and now Head of Research Breeding Laboratories at Vilmorin SA in Montpellier, France.
2. Images to accompany this press release can be downloaded from: http://bit.ly/2ewVXrT
3. If you have any questions or would like to interview Professor Brown please contact:
Head of External Relations (interim)
4. Septoria infection is characterized by the growth of necrotic brown lesions on wheat leaves, which lead to a significant reduction in crop yield and quality, with reported yield losses as high as 50%. It is a major disease of wheat in many temperate countries throughout the world. Favourable weather conditions mean it is most severe in Ireland. Resistance to Septoria is now categorized as being of very high importance as a trait on the AHDB Recommended List of Wheat Varieties.
5. About the John Innes Centre
The John Innes Centre is an independent, international centre of excellence in plant science and microbiology.
Our mission is to generate knowledge of plants and microbes through innovative research, to train scientists for the future, to apply our knowledge of nature's diversity to benefit agriculture, the environment, human health and wellbeing, and engage with policy makers and the public.
To achieve these goals we establish pioneering long-term research objectives in plant and microbial science, with a focus on genetics. These objectives include promoting the translation of research through partnerships to develop improved crops and to make new products from microbes and plants for human health and other applications. We also create new approaches, technologies and resources that enable research advances and help industry to make new products. The knowledge, resources and trained researchers we generate help global societies address important challenges including providing sufficient and affordable food, making new products for human health and industrial applications, and developing sustainable bio-based manufacturing.
This provides a fertile environment for training the next generation of plant and microbial scientists, many of whom go on to careers in industry and academia, around the world.
The John Innes Centre is strategically funded by the Biotechnology and Biological Sciences Research Council (BBSRC). In 2015-2016 the John Innes Centre received a total of £30.1 million from the BBSRC.
The John Innes Centre is the winner of the BBSRC's 2013 - 2016 Excellence With Impact award.
6. About the BBSRC
The Biotechnology and Biological Sciences Research Council (BBSRC) invests in world-class bioscience research and training on behalf of the UK public. Our aim is to further scientific knowledge, to promote economic growth, wealth and job creation and to improve quality of life in the UK and beyond.
Funded by Government, BBSRC invested over £473M in world-class bioscience in 2015-16. We support research and training in universities and strategically funded institutes. BBSRC research and the people we fund are helping society to meet major challenges, including food security, green energy and healthier, longer lives. Our investments underpin important UK economic sectors, such as farming, food, industrial biotechnology and pharmaceuticals.
For more information about BBSRC, our science and our impact see: http://www.bbsrc.ac.uk
For more information about BBSRC strategically funded institutes see: http://www.bbsrc.ac.uk/institutes
Molecular Plant Pathology