Three British rust fungi reported to form aecia on daisy (Bellis perennis) are compared. A recently discovered species, possibly introduced from Australia, is identified as Puccinia distincta. It is a short-cycled -opsis form lacking uredinia, with aecia and telia confined to Bellis and its aeciospores capable of reinfecting the same host. This rust is compared with a macrocyclic heteroecious eu-form, P. obscura, which produces pycnia and aecia on Bellis and uredinia and telia on Luzula. Puccinia distincta is probably derived from and correlated with P. obscura because both species have the same aecial host, and because their teliospores are closely similar in morphology and dimensions. Comparison is extended to P. lagenophorae, a common rust with aecia and telia on Senecio spp., which has been reported to form aecia on Bellis following inoculation with aeciospores from Senecio. The repeated failure of our own reciprocal inoculation experiments using aeciospores from the two different hosts and differences in teliospore morphology between P. distincta and P. lagenophorae lead us to conclude that the current rust epidemic on daisies is caused by P. distincta which is distinct from P. lagenophorae.
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