Characterization of Uromyces muscari and first confirmed report on Muscari armeniacum in Hungary

Muscari species are widely cultivated, popular ornamental plants in Europe, but are susceptible to rust fungi, which can substantially reduce their aesthetic value and overall fitness. In May 2023, characteristic rust fungus-like symptoms were observed on M. armeniacum plants in Solymár (Hungary). The causal agent, designated as isolate UmHu2, was identified as Uromyces muscari based on morphological studies and results of molecular phylogenetic analyses, which included three reference specimens from Hungary and one from Canada collected on other Muscari species. Features of the rust infections and spores produced were consistent with previous descriptions. Sequences generated four gene regions, ITS and LSU rDNA, β-tubulin and translation elongation factor 1-alpha, showed 98-100 % identity and grouped with strong support together in multi-gene maximum likelihood phylogenetic analyses with selected Pucciniaceae rusts. Pathogenicity was confirmed by artificial inoculation of healthy M. armeniacum plants. Microscopic investigation and sequencing verified consistency with the inoculum, thereby fulfilling Koch's postulates. Cross-infection experiments demonstrated that U. muscari isolates from different Muscari species are genus-specific but not species-specific. To our knowledge, this is the first report of U. muscari infecting M. armeniacum in Hungary.