Distribution and frequency of mating types of Rhynchosporium commune in central Alberta

Abstract

Rhynchosporium commune, the cause of barley scald, is an important disease of barley in Canada. Multiple studies have indicated that cryptic sexual reproduction may occur between opposite mating types (MAT1-1 and MAT1-2). The occurrence of R. commune mating types in Canada has not been determined previously. Infected leaves from barley cultivars in seven commercial fields and three breeding nurseries in central Alberta were collected and subjected to multiplex PCR to assess the presence of scald mating types within the lesions. Mating types were determined in 410 scald lesions from 288 leaves. Over 10% of lesions contained both mating types, and 44% of leaves with more than one lesion analyzed were colonized by both mating types. The mating types significantly deviated from the 1:1 ratio that would have been expected with frequent sexual reproduction. MAT1-2 was more common in six of the ten locations and for the region as a whole. The presence of both mating types, often in close proximity to each other, suggests that the cryptic sexual stage could be present in Alberta if it does occur. The skewed mating type ratio does suggest, however, that asexual reproduction is predominant within the pathogen population.