Resistance to Rhynchosporium secalis in a cross between winter and spring barley

Winter barley types shows higher levels of field resistance to R. secalis compared to spring barley varieties. In addition, barley leaves have been shown to tolerate relatively high levels of R. secalis colonisation in the absence of visible symptoms, suggesting that suppression of symptom expression may be an alternative mechanism of resistance. This study examined resistance in 191 DH lines from a cross between spring variety Cocktail, and a winter parent derived from a cross between Leonie and Pearl. Field resistance was scored by measuring visible symptoms and also by R. secalis specific qPCR of sampled leaves. Two novel resistance QTL (on chromosomes 2H and 7H) were identified, which affected both pathogen colonisation and visible symptoms. These were not associated with genes controlling winter/spring growth habit. A further QTL (on chromosome 5H) was identified as affecting relative expression of disease symptoms