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Barley is the second most important cereal crop grown in the UK - used as animal fodder, in human foods such as health foods, soups and stews, and also in the drinks production industry.  High quality malting barley underpins beer and whisky production and is worth around £20 billion to the UK economy. However, barley is susceptible to a number of diseases, the most important of which is called leaf blotch (Rhynchosporium commune) and is caused by a fungal pathogen.  This disease affects the leaves, ears and stems of the barley – decreasing grain quality and reducing crop yields by up to forty per cent.
 

Bruce Fitt, professor of plant pathology at the University of Hertfordshire, said: "Crops that appear to be clear of disease can suddenly develop leaf blotch symptoms unexpectedly.  The source of the disease is unclear and this has puzzled farmers and researchers alike.
 

Grass margins possible source of disease

"However, our research shows that the fungal pathogen that causes barley leaf blotch can be found on wild ryegrasses which are common both as weeds within cereal crop fields and in the surrounding field margins."
 

In the study, both DNA and plant testing showed that the leaf blotch pathogen that affects barley can be found on the wild grasses and was virulent on commonly grown varieties of barley. Furthermore, these data suggest that ryegrasses could potentially be a reservoir of R. commune inoculum able to initiate barley leaf blotch epidemics. Similar roles for wild grasses as potential sources of inoculum have been suggested previously for the wheat pathogens Pyrenophora tritici-repentis (cause of tan spot), Oculimacula yallundae (synonym Tapesia yallundae, cause of eyespot).
 

Professor Fitt continued: "Field margins play an important role in creating areas of habitat to support wildlife and wild plants species. But the increasing demand for agricultural land to provide enough crops to feed and support the growing population is putting pressure on these little pockets of wild nature.
 

"And if this pathogen species can be spread from wild grasses onto barley crops and back again, further investigation is needed to identify how widespread this species is and also the role that wild grasses play as sources of disease for other crops such as wheat."

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