Resistance to barley scald (Rhynchosporium secalis) in wild barley grass (Hordeum glaucum and Hordeum leporinum) populations in south-eastern Australia

Abstract

Plants from 22 wild barley grass populations, 10 Hordeum glaucum, 11 Hordeum leporinum, and one mixed population, were inoculated with seven isolates of Rhynchosporium secalis originally collected from H. leporinum plants. There was substantial variability for resistance within and among populations from both Hordeurn species, but H. glaucum was: on average more resistant than H. leporlnum. Individual populations often responded differentially to the R. secalis isolates, being resistant to some isolates and susceptible to others. Differential responses were more pronounced among H. glaucum populations. No consistent geographic correlations between level of resistance within a population and geographic location were found, indicating that large scale trends for resistance do not exist in either H. gluucum or H. leporinwm. The existence of widespread resistance variation in both wild barley grasses may create substantial selection pressures favouring the emergence of variability for pathogenicity in R. secalis, which would complicate efforts to breed for R. secalis resistance in cultivated barley.