The epidemiological importance of asymptomatic infection of winter barley by Rhynchosporium secalis and its consequences for crop protection and breeding

Summary: Leaf scald (caused by Rhynchosporium secalis) is one of the most economically important diseases of barley. Data were collected from three seasons of trials using two susceptible winter barley cultivars (Sumo and Saffron) and two resistant cultivars (Flagon and Manitou). Levels of R. secalis DNA were quantified from several growth stages (GS) throughout the growing season and visual symptoms assessed. Results demonstrate that the pathogen was able to colonise and sporulate extensively on apparently healthy leaves, and spread to grain without symptoms being seen in the crop. This raises questions about how the fungus interacts with the plant, what triggers lesions to develop and the role of asymptomatic infection in pathogen spread, plant defence and crop yield.