GENETIC VARIABILITY AND PATHOGENICITY AMONG POLISH ISOLATES OF BIPOLARIS SOROKINIANA FROM SPRING BARLEY
The fungal pathogen Bipolaris sorokiniana (Cochliobolus sativus) is the causal agent of severe barley diseases. This study was conducted due to the economic importance of the diseases it induces and the lack of data on its population diversity in Poland. The principal aims of this study were: (i) determination of the intraspecific genetic variability of the pathogen using random amplified polymorphic DNA (RAPD) analysis and (ii) assessment of the pathogenicity of 95 B. sorokiniana isolates obtained from different plant parts and cultivars, collected from various locations and cropping systems in 2002-2006. Out of 180 analyzed primers, nine, producing 29 reproducible polymorphic fragments, were retained for RAPD analysis. The UPGMA analysis showed genetic variability among isolates but did not reveal a clear effect of any factor. This suggests that the variation is probably caused by an interaction of various factors. AMOVA showed that geographic origin, cultivation system, cultivar and, in some cases, the plant organ may affect genetic diversity. Pathogenicity tests showed that all isolates were pathogenic to barley seedlings of cv. Justina. ANOVA revealed significant differences in the pathogenicity of the isolates. Most of them showed a higher ability to cause lesions on roots than leaves. There was a negative correlation between the pathogenicity of the isolates towards roots and their weight and no significant correlations between pathogenicity and mycelium morphology or origin of isolates from different plant parts.