Inoculation of known and potential alternate hosts with Peridermium pini and Cronartium flaccidum aeciospores

The ability of Peridermium pini and Cronartium flaccidum aeciospores and my celium to infect known (Vincetoxicum spp., Pedicularis spp., Paeonia spp.) and potential (Melampyrum spp., Pyrola sp., Dactylorhiza sp., Solidago sp., Salix sp., Geranium sp. and Maianthemum sp.) alternate hosts was tested. N one of the mycelial cultures and only 10% of the aeciospore samples produce d uredinia or telia on the tested species suggesting that most aeciospores in Finland belong to the autoecious P. pini. Aeciospores from three locatio ns in northern Finland, however, produced uredinia or telia on Vincetoxicum mongolicum, V. nigrum, V. fuscatum, Paeonia anomala, three P. officinalis cultivars, Melampyrum sylvaticum and Pedicularis palustris either in vitro or in vivo, indicating that these aeciospores belong to the heteroecious C. flaccidum, which occurs sporadically in Finland. interestingly the host-sp ecificity of C. flaccidum encountered in Finland was very low (e.g, one sam ple produced uredinia or telia on eight species). This, added to the wide d istribution of Melampyrum spp. over northern Fennoscandia, suggests that th e main alternate hosts for C. flaccidum in Finland may be in Melampyrum rat her than Pedicularis.