Genetic variation, pathogenicity and mycelial growth rate differentiation betweenGaeumannomyces graminisvar.triticiisolates derived from winter and spring wheat

The variability ofGaeumannomyces graminisvar.tritici(Ggt) isolates was evaluated at an intravarietal level using non‐molecular and molecular methods. Pathogenicity and linear growth rate of the pathogen were estimated. Very high pathogenicity was found in 44% of the isolates, medium in 20% and low only in 8%. Significant differences in mycelial growth rate were observed. The quickest linear growth rate ofGgtmycelium was observed at 25°C. Isolates derived from winter wheat grew faster than those obtained from spring wheat. The correlation between growth rates and pathogenicity was not significant. DNA polymorphism determined by random amplified polymorphic DNA (RAPD)–PCR was used to assess genetic variation among isolates. Thirty‐two RAPD markers revealed DNA polymorphism suitable for assessing variability among isolates examined. Cluster analysis of RAPD data identified a few groups of isolates. RAPD markers associated with pathogenicity as well as mycelium growth rate were found.