First European records of <i>Puccinia modiolae</i> and <i>P. platyspora</i> , two native South American rust fungi, and new observations on their life cycle and morphology

This paper reports the South American rust fungi <i>Puccinia modiolae</i> and <i>P. platyspora</i> (Pucciniales/Uredinales) as new alien species of the European rust funga. <i>Puccinia modiolae</i> is presently known from Switzerland and Germany, <i>P. platyspora</i> from Switzerland, Germany, and France. The records of <i>P. platyspora</i> are 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 <i>CO3</i> (cytochrome <i>c</i> oxidase III) gene. <i>Puccinia modiolae</i> and <i>P. platyspora</i> have been recorded so far in Europe on members of the genera <i>Alcea</i>, predominantly on <i>Alcea rosea, Althaea</i>, and <i>Malva</i> of the Malvaceae, subfam. Malvoideae. <i>Alcea rosea</i> is host of both species and shared also with the common mallow rust, <i>P. malvacearum</i>, 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 <i>P. platyspora</i> can 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 <i>P. malvacearum</i>, 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.