Pathogenic Variation of Rhynchosporium secalis Isolates from Ethiopia

Abstract

Rhynchosporium secalis, the causal agent o f barley leaf scald is a highly variable pathogen in areas where the disease is reported. To design an effective breeding program and exercise other disease control practices, information on the pathogenic variability of this pathogen is critical. In this study, the variability of 24 single spore isolates was studied on seedlings and adult plants of 14 barley differentials. Seedlings test showed wide variability o f the pathogen in that the 24 isolates were grouped into 17 distinct pathotypes. Pathotypes E tl6 and E tl7 were the most virulent and overcame the resistance in 11 differential genotypes whereas pathotypes E tl, Et2 and Et3 were virulent on only one genotype each. Environmental conditions, farming practices and the cultivation of barley largely as landrace populations are assumed to generate variability o f the pathogen in Ethiopia. In general, there was a strong correlation between the seedling and adult plant tests. Since scald is most destructive at early crop growth stages, seedling resistance is vital to reduce the disease epiphytotics, to differentiate isolates and to predict adult plant resistance. The shifts in population composition and the greater variability of R. secalis detected in this study suggest regular sampling of the pathogen within a given region is warranted.