The development of Ramularia leaf spot disease in barley

The fungus Ramularia collo-cygni (Ascomycotina) has recently become an important pathogen of barley (Hordeum vulgare), causing leaf spotting on upper leaves. McGrann and Brown studied the factors that cause this fungus to change from a harmless endophyte to an aggressive, necrotrophic parasite, contrasting susceptible varieties with one which has strong partial resistance.

Typical disease symptoms on Braemar (i), Power (ii) and Golden Promise (iii) 21 days post-inoculation.

Changes in concentrations of reactive oxygen species in host leaves caused leaf spot symptoms to develop, but foliar senescence alone did not cause disease expression. A better understanding of the aetiology of Ramularia leaf spot can lead to improvements in methods of selecting barley varieties with stronger partial resistance.