In this study, growth rate of the fungus Chalara fraxinea in pure culture was evaluated. 12 different isolates of the fungus (6 from Poland, 6 from Slovenia) were included to the assay. They were grown on 8 types of growth media (MEA, MEA with streptomycin sulphate, PDA, WA, Czapek agar, agar with beech, agar with flowering ash and agar with common ash extract) in 3 replicates. Colony diameters were measured regularly, within 8 weeks. Colony growth rate was calculated for each culture media and statistic analysis with one-way ANOVA and Kruskal-Wallis test was performed. Fungal isolations from 3-4 year old common ash (Fraxinus excelsior) trees, affected by ash dieback, were made. Results showed variability in growth rate between isolates and on different types of growth media, however, no clear regularities were indicated. Colony growth rate was higher on PDA and on growth media with wood extracts. The fungus growth on growth media with wood extract does not show actual tree species susceptibility to the disease since growth on beech extract medium was high. Growth rate of slovenian isolates was higher on most of the media, probably because of older isolates. The relatively low fungal growth rate on MEA was similar to that described in literature.
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