Ramularia collo-cygni: the biology of an emerging pathogen of barley

Abstract

Ramularia collo-cygni is now recognized as an important pathogen of barley in Northern Europe and New Zealand. It induces necrotic spotting and premature leaf senescence, leading to loss of green leaf area in crops, and can result in substantial yield losses. The fungus produces a number of anthraquinone toxins called rubellins, which act as host nonspecific toxins with photodynamic activity. These toxins induce lipid peroxidation and are possibly the cause of the chlorosis and necrosis observed in leaves infected with R. collo-cygni. The fact that the fungus can remain latent in barley plants until flowering, coupled with its very slow growth in vitro, makes it difficult to detect in crops. As a result, the epidemiology of this pathogen remains poorly understood. However, the recent development of rapid and reliable PCR methods for specific detection of R. collo-cygni offers the prospect of increased understanding of its epidemiology and improved disease control.

Brachypodium as an emerging model for cereal–pathogen interactions

“…were found to form hyphal aggregates (infection plaques) under which penetration holes are formed, which is strikingly similar to the infection process described in wheat (Daniels et al, 1991). Infection of brachypodium with R. collo-cygni resulted in hyphal emergence from stomata on the abaxial surface, as occurs in barley (Walters et al, 2008). Peraldi et al (2013) reported variation in resistance of the two ecotypes assessed, with Bd3-1 more susceptible than Bd21 to eyespot caused be either O. acuformis or O. yallundae.…”

“…Ramularia leaf spot (RLS), caused by the necrotrophic pathogen R. collo-cygni, has recently been identified as an important pathogen of barley in northern Europe (Walters et al, 2008). RLS initially presents as brown/black leaf spots, with the surrounding leaf area subsequently becoming rapidly chlorotic then necrotic (Walters et al, 2008).…”

“…RLS initially presents as brown/black leaf spots, with the surrounding leaf area subsequently becoming rapidly chlorotic then necrotic (Walters et al, 2008). The reduction in photosynthetic capacity due to rapid leaf senescence induced by RLS can result in considerable yield loss and loss of grain quality (Oxley and Havis, 2004).…”

“…The reduction in photosynthetic capacity due to rapid leaf senescence induced by RLS can result in considerable yield loss and loss of grain quality (Oxley and Havis, 2004). Although currently RLS is only economically significant for barley cultivation, it has also been identified on wheat and oats (Walters et al, 2008). Peraldi et al (2014) have demonstrated that brachypodium can be infected with eyespot and RLS, and exhibits similar symptoms (Fig.…”

Host and Nonhost Response to Attack by Fungal Pathogens

“…Due to virtually still lacking information about plant responses to this pathogen, I will only briefly mention it referring to one review and some original literature addressing the pathogen and disease (Walters et al 2008). The fungus enters its host via stomatal openings and grows in the leaf mesophyll where it induces necrosis that becomes visible as dark spots approximately 7 days after inoculation in controlled conditions (Stabentheiner et al 2009).…”