First European records of Puccinia modiolaeand P. platyspora, two native South American rust fungi, and new observations on their life cycle and morphology

ABSTRACTThis paper reports the South American rust fungi Puccinia modiolaeand P. platyspora(Pucciniales/Uredinales) as new alien species of the European rust funga. Puccinia modiolaeis presently known from Switzerland and Germany, P. platysporafrom Switzerland, Germany, and France. The records of P. platysporaare the first ones from outside South America. The specimens were identified by teliospore characters and sequences of the nuclear ribosomal DNA (internal transcribed spacer 2 and domains D1–D2 of the nuclear ribosomal large subunit) and the mitochondrial CO3(cytochrome coxidase III) gene. Puccinia modiolaeand P. platysporahave been recorded so far in Europe on members of the genera Alcea, predominantly on Alcea rosea, Althaea, and Malvaof the Malvaceae, subfam. Malvoideae. Alcea roseais host of both species and shared also with the common mallow rust, P. malvacearum, allowing for mixed infections. The plant is commonly grown as an ornamental and may play a major role for the spread of the alien Malvaceae rust fungi. It was observed for the first time that P. platysporacan produce spermogonia and aecidium-type aecia, suggesting phenotypic plasticity regarding the formation of spore states. The observed spermogonia mainly remained closed and did not liberate spermatia. They produced telio- and aeciospores besides spermatia in their cavity and eventually converted entirely into telia or, rarely, into aecidium-like sori. Small clusters of aeciospores and peridial cells were commonly found hidden in the telial plectenchyma, and well-developed aecidium-type aecia provided with a peridium developed rarely in the center of mature telia. Spermogonia belonging to group V type 4 were found in P. malvacearum, which is generally supposed to lack spermogonia. Some spermogonia produced only spermatia in their cavity; others formed spermatia and teliospores, and some eventually converted into telia.