Current virulence of Pyrenophora teres on barley in Western Australia

Studies on variation, occurrence, and distribution of virulence in Pyrenoph ora teres are helpful to identify effective sources of resistance that can be used for barley breeding in Western Australia. Seventy-nine isolates of Pyrenophora teres were collected from different barley fields of Western Au stralia in 1995-96. Seventy-four induced net type symptoms (P. teres f. ter es) and five induced spot type symptoms (P. teres f. maculata). Net type is olate responses on 47 barley lines were similar to the range of responses i nduced by mine historical isolates collected in the region between 1975 and 1985. These net type isolates were classified into two distinct groups bas ed on virulence to the cultivar Beecher. Isolates were further classified i nto eight groups based on minor pathogenic variation among the population. The virulence phenotype present in an eastern Australian isolate was not ob served in any isolates collected from Western Australia. An analysis of var iance on a subset of 12 net type isolates indicated a significant line x is olate interaction (P < 0.001), with the interaction term variance component four times larger than the error variance. Based on these studies, the vir ulence among net type isolates has remained stable in Western Australia for the last 19 years. Spot type isolates were collected from a wider geograph ic area than previously reported and varied in virulence based on response to barley line Herta. Variation in spot-type isolates is reported for the f irst time from the region. The results from this study are being used in th e development of resistant varieties.