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Studies of the mating systems of basidiomycetous yeasts from oceanic regions demonstrate that Rhodosporidium bisporidiis sp. n. and Rhodosporidium dacryoidum sp. n. have tetrapolar mating factors. Rhodosporidium infirmo-miniatum sp. n. is bipolar with three known alleles. The formal description of these three species is presented, as well as that of Rhodosporidium capitatum sp. n., a self-sporulating form. Rhodosporidium capitatum and Rhodosporidium bisporidiis are distinguished by the formation of basidia with terminal sporidia that develop on primary sporidia. The sporidia are not forcefully ejected. Rhodosporidium infirmo-miniatum has short basidia with terminal sporidia, but lacks primary sporidia. Rhodosporidium dacryoidum has two- to four-celled basidia with lateral sporidia. Rhodosporidium capitatum, Rhodosporidium infirmo-miniatum, and Rhodosporidium bisporidiis produce endospores. The taxonomic status of these species, and of the basidiomycetous yeast-like genera, is discussed.

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Rhodosporidium paludigenum sp. nov. 'has the phenotypic characteristics of the imperfect yeast Rhodotorula graminis and a bipolar incompatibility mating system, and is not sexually compatible with other Rhodosporidium species. The type strah of this new species is CBS 6566.Sexuality in the genus Rhodotorula Harrison was first reported by Banno (1) with the description of Rhodosporidium toruloides Banno 1967. The genus has since been expanded to include eight species (2). During a review of the genus for a new edition (Kreger-van Rij, in preparation) of The Yeasts, a Taxonomic Study (3), we exammed a previously undescribed species from intertidal waters of south Florida in mangrove (Rhizophora mangle L.) swamps and black rush (Juncus roemerianus Scheele) marshes. The imperfect stage of this yeast has the characteristics of Rhodotorula graminis di Menna 1958, which is differentiated from other members of the genus Rhodotorula by the ability to assimilate nitrate (as KN03) as a sole source of nitrogen and the inability to utilize melezitose as a sole source of carbon (4). These isolates of R. graminis from intertidal sources were found to have a basidiomycetous life cycle when they were mixed on corn meal agar. The life cycle is heterothallic; cells from opposite mating types conjugated with the development of mycelia with clamp connections and round teliospores. The teliospores germinated to produce septate metabasidia with lateral and terminal basidiospores. We isolated the basidiospores by micromanipulation, followed by culturing and mating studies, and found only the parental mating types. This indicates that sexuality consists of a bipolar incompatibility system (5).Rhodosporidium malvinellum Fell et Hunter 1970 is the only other species of Rhodosporidium with the phenotypic characteristics of Rhodotorula graminis. Rhodosporidium malvinellum and the new species are distinct, as suggested by differences in their colony colors: Rhodosporidium malvinellum has a distinct mauve color in contrast to the salmon-orange color of the new species. The species distinction is confirmed by mating experiments which demonstrate that the two species do not intermate. Neither Rhodosporidium malvinellum nor the new species mates with the type strain of Rhodotorula graminis (CBS 2826), suggesting that the imperfect state of Rhodotorula graminis represents more than two sexual species. A similar situation is present with Rhodotorula glutinis (Fres.) Harrison 1852, which consists of three sexual species (Rhodosporidium sphaer-