Sequencing genes of major barley disease an important step towards better control

Scientists at Scotland’s Rural College, together with colleagues at the University of Edinburgh and Rothamsted Research, have unravelled the genome of Ramularia, a fungal disease attacking barley crops. The work, funded by Scottish Government, opens the way to find better ways of controlling a pathogen that can reduce yields by as much as 20%.

The study is published this week in the journal BMC Genomics

Ramularia’s characteristic square leaf spots, surrounded by a typical yellow halo, were first noticed in Italy over one hundred years ago. However it is only within the last 30 years that the disease has become a significant problem for farmers growing a crop of major importance to the brewing, distilling and feed markets. It affects both yield and grain quality.

Working with cutting-edge technologies at the University of Edinburgh's Edinburgh Genomics facility, the SRUC-led team produced a first look at what makes this devastating pathogen tick.

“What excites us about this latest advance is the ability it gives us to really investigate what make the fungus tick and why it behaves the way it does,” Says Dr Neil Havis, a world expert and a member of SRUC’s Crop and Soils team. “For example we know the Ramularia collo-cygnifungus lives inside growing barley plants with no ill effect until after the barley flowers or becomes stressed. It is then, with the swelling of the barley grains, that the fungus attacks its host with toxins, just at a time when we can do little about it.”

This project is a culmination of over 15 years of research into Ramularia at SRUC. For SRUC researcher Dr Graham McGrann, who completed the sequencing of the genome, there are additional opportunities on the horizon. “From studying their genomes we now know that Ramularia, which attacks barley, is closely related to Septoria, the major fungal disease of wheat crops across the world. They are distinct organisms but because of the close relationship between the two fungi our work on a barley disease could help wheat growers as well.”

Researchers at SRUC are already thinking about the next steps and using the knowledge of gene sequences to delve deeper into fungal behaviour.

“We found very few genes that produce enzymes able to degrade plant cell walls,” explains Dr McGrann. “This might be associated with the way the fungus stealthily avoids detection by the plant’s defences but is then able to turn and attack its host. Understanding the triggers for this switch may provide novel control strategies for this important disease.”

For Neil Havis a key issue is what stimulated Ramularia to change from being a relatively unimportant pathogen to one which is now so harmful.

“Are there answers contained in what we now know about the genomes of both barley and Ramularia that can help us? Or was there something about our selection of barley varieties, the way we grow the crop or the changing climate that suddenly made conditions so much better for the disease? If this latest breakthrough helps us address questions like that farmers, brewers, distillers and consumers will benefit."

For More information on the sequencing of the Ramularia genome contact Dr Neil Havis , neil.havis@sruc.ac.uk; Dr Graham McGrann,graham.mcgrann@sruc.ac.uk (both 0131 535 400) or Professor Mark Blaxter, the University of Edinburgh's Institute of Evolutionary Biology and Edinburgh Genomics facility, mark.blaxter@ed.ac.uk .