Artificially applied late-terminal drought stress in the field differentially affects Ramularia leaf spot disease in winter barley

Ramularia leaf spot disease (RLS) is one of the most dominating fungal diseases in barley. The disease typically appears late in the season after flowering and results in a rapid loss of photosynthetic leaf area. A recent decline in fungicide efficacy and a lack of RLS-resistant cultivars hamper effective control. Global warming will provoke increasing droughts which influence host plant physiology and probably affect outbreak and severity of RLS. Relatively little is known about genetic resistance to RLS in winter barley and about the influence of various weather conditions and climate change on RLS pathogenesis. Hence, we evaluated severity of RLS on 15 winter barley genotypes under persistent late-terminal drought stress or controlled irrigation, respectively, in a field rainout shelter. Over three consecutive years, we observed reproducible differences in quantitative RLS field resistance of the used cultivars and variable suppression of RLS under drought. Our results support a function of drought in suppression of RLS in winter barley, but also reveal strong year effects even under semi-controlled rainout shelter conditions. Data may be relevant for genotype selection in breeding programmes for RLS resistance and for farmers in the frame of integrated disease management under a changing climate. Graphical abstract: [Figure not available: see fulltext.]