Ramularia collo-cygni: a new pathogen spreading in barley fields in Estonia

Ramularia leaf spot (RLS) caused by the fungus Ramularia collo-cygni (Rcc) is affecting barley fields throughout temperate regions worldwide. The first finding of RLS in Estonia was reported on spring barley in 2012 and since then the area of RLS infection has been widening in Estonia. This work has been carried out to monitor the natural infection of Rcc in two winter barley cultivars and to follow artificial fungal infection by a PCR-based assay. Using our approach, we could detect presence of the fungal pathogen in barley leaves before the appearance of disease symptoms at early growth stages. Response of two tested cultivars to Rcc infection in the field conditions was different, showing genotype-environment interaction in the development and spreading of Rcc. In harvested grain samples at the end of growing season no Rcc infection was detected. The role of external inoculum, Rcc conidia transmitted from various grasses (Poaceae) growing next to crop fields, is discussed. These results provide further insight into the epidemiology of Rcc.