Rhynchosporium commune (formerly known as R. secalis) is one of the most important diseases of barley, particularly in wet seasons and in high humidity areas. The disease is called ‘rhynchosporium’, ‘scald’ or ‘leaf blotch’ and is one of the most destructive pathogens of barley worldwide, causing disease which decreases yield by up to 40% and reduces grain quality.
Rhynchosporium is a polycyclic disease, with the primary inoculum including conidia produced on crop debris, infected seeds and possibly as yet unidentified ascospores. Secondary disease spread is primarily by splash dispersal of conidia produced on infected leaves, which may be symptomless early in the growing season. Symptomless-infection and sporulation can also occur on ‘resistant’ cultivars. Similarly ‘susceptible’ cultivars do not always become symptomatic.
R. commune is highly variable in pathogenicity, virulence, sporulation and germination rates specificity, colony morphology and colour, fungicide resistance, isozymes and DNA molecular markers. Population genetics based on such markers indicates that the sexual stage, ascospores, is likely to exist.
Symptoms
Symptoms first appear as chlorotic, irregular or diamond-shaped lesions. Later symptoms are typically blue-grey water-soaked lesions on leaves and leaf sheaths. Mature lesions become pale brown with a dark purple margin. As they grow they merge forming large areas of dead tissue, even destroying the whole plant leaf area.
Our work on rhynchosporium falls into three main areas:
- resistance genetics
- pathogen genomics and molecular interactions
- epidemiology, crop protection and resistance deployment.
Key review references
Walters, D., Avrova, A., Bingham, I.J., Burnett, F.J., Fountaine, J., Havis, N.D., Hoad, S.P., Hughes, G., Looseley, M., Oxley, S.J.P., Renwick, A., Topp, C.F.E., Newton, A.C. 2012. Control of foliar diseases in barley: towards an integrated approach. European Journal of Plant Pathology 133, 33-73.
Thirugnanasambandam, A., Wright, K.M., Atkins, S.D., Whisson, S.C., Newton, A.C. 2011. Infection of Rrs1 barley by an incompatible race of the fungus Rhynchosporium secalis expressing the green fluorescent protein. Plant Pathology 60, 513–521.
Zhan, J., Fitt, B.D.L., Pinnschmidt, H.O., Oxley, S.J.P., Newton, A.C. 2008. Resistance, epidemiology and sustainable management of Rhynchosporium secalis populations on barley. Plant Pathology 57, 1-14.
