Abstract
Inoculation tests using Mycopappus alni isolates, the frosty mildew fungus of Crataegus chlorosarca (Rosaceae), were performed for leaves of 21 tree species in 15 genera of Betulaceae, Rosaceae, Fagaceae, Juglandaceae and Hamamelidaceae. The M. alni isolate caused obvious lesions with propagules on leaves of 14 species in Betulaceae, Rosaceae, Juglandaceae and Hamamelidaceae, suggesting its pathogenicity to those species. In Fagaceae, the isolate caused lesions on leaves of Fagus crenata and Castanea crenata, suggesting its pathogenicity to both species. However, the virulence of the isolate to those species is thought to be weak because formation of the lesions and propagules was less frequent than species in other families. The isolate caused no lesion on leaves of Quercus spp., suggesting no pathogenicity to Quercus species. Microscopic observations revealed that the fungus invades C. chlorosarca leaves through stomata.
