Characterization and distribution of pathogenic variation inPyrenophora teresf.teresandP. teresf.maculatafrom western Canada

Abstract

Two hundred and nineteen isolates of Pyrenophora teres, collected in western Canada, together with five reference cultures, were characterized by their reaction on 12 barley differentials. Eighty-two percent of isolates were of the net symptom producing form, P. teres f. teres and 18% were of the spot form, P. teres f. maculata. The net and spot forms of P. teres were further differentiated into 45 and 20 pathotypes, respectively. The pathogenic variability detected was considerably greater than previously reported. Whereas P. teres f. teres was distributed generally throughout the Prairie Provinces, P. teres f. maculata was most prevalent in Saskatchewan where it composed 35 percent of isolates. The eight most commonly grown malting and feed barley cultivars in western Canada were largely susceptible to 19 representative pathotypes of P. teres. Leduc, a six-rowed feed barley registered in 1985, had the best overall resistance. The susceptibility of barley cultivars currently being grown in western Canada to P. teres and the identification of isolates virulent on resistance sources being used in breeding programs indicates that incorporating resistance and identifying new resistant germplasm should remain a high priority.