1380 Mycologia, 96(6), 2004, pp. 1380–1385.  2004 by The Mycological Society of America, Lawrence, KS 66044-8897 Nematococcomyces rhododendri, a new species in a new genus of the Rhytismatales from China Cheng-Lin Hou Meike Piepenbring Botanisches Institut, J.W. Goethe-Universita ¨t Frankfurt am Main, 60054 Frankfurt/M., Germany Franz Oberwinkler Spezielle Botanik, Eberhard Karls Universita ¨t, Auf der Morgenstelle 1, 72076 Tu ¨bingen, Germany Abstract: A fungus belonging to the Rhytismatales found on twigs of Rhododendron lutescens in Yunnan, southwestern China, is described as a new species in a new genus. It is characterized by Coccomyces-like as- comata but differs in having elliptical ascospores with filiform, hyaline appendages. The ascospores of this new taxon are somewhat similar to those of species of Parvacoccum, but the latter has symmetrical, fusi- form ascospores with funnel-shaped appendages. The new genus also is distinct from Hypoderma, Hy- podermella, Myriophacidium, Ploioderma, Neococcomy- ces and Therrya. Key words: Discomycetes, plant pathogen, Rho- dodendron, Rhytismataceae INTRODUCTION Fungi belonging to the Rhytismatales are distributed worldwide and many of them are plant pathogens, some of which cause economically important diseases of trees (Cannon and Minter 1986). Hawksworth et al (1995) included three families in the Rhytismata- les, Ascodichaenaceae, Cryptomycetaceae and Rhytis- mataceae (syn. Hypodermataceae), but Kirk et al (2001) considered the Crytomycetaceae to be a syn- onym of the Rhytismataceae. Members of the Rhytis- mataceae usually have ascomata that are more or less embedded in host tissue and open by longitudinal or radial splits, thin-walled, J- asci and ascospores usu- ally with gelatinous sheaths (Sherwood 1980, Di- Cosmo et al 1984, Cannon and Minter 1986, John- ston 1986, Livsey and Minter 1994). The Ascodi- chaenaceae have erumpent ascomata and ascospores without gelatinous sheaths. Members of the Phacidi- aceae, which have J+ asci, ascospores without a ge- Accepted for publication April 8, 2004. Corresponding author. E-mail: chenglin@em.uni-frankfurt.de latinous sheath, and conidia with mucous append- ages on both ends, are separated from the Rhytis- matales and placed in the Helotiales (syn. Leotiales) (DiCosmo et al 1984). The morphology of ascomata and ascospores is im- portant in the classification of the Rhytismataceae at the generic level (Darker 1967). Many new genera were erected based on ascospore shape, characteris- tics of ascomata and the depth to which ascomata are embedded in host tissue. Although most mycologists argue that some aspects of Darker’s system are arti- ficial and unsatisfactory, no suitable alternative has been proposed yet. Cannon and Minter (1986) large- ly adopted Darker’s system in their monograph for the Rhytismataceae on the Indian subcontinent, as have a number of other authors (Powell 1974, Sher- wood 1980, Minter et al 1987). Johnston (1988, 1989) attempted to use aspects of ascomatal devel- opment to define genera of the Rhytismatales, and some new genera were erected ( Johnston 1990, 1991). Other mycologists, however, still use Darker’s system (Hunt and Funk 1988, Merrill et al 1996, Minter et al 1998, Lin et al 1999). Therefore we ac- cept the generic classification and the system elabo- rated by Darker (1967) and Cannon and Minter (1986) in the current paper. The Rhytismatales have been well documented in Europe, North America, Australia, the Indian sub- continent and parts of southeastern Asia (Darker 1932; Minter 1981; Cannon and Minter 1986; John- ston 1986, 1989; Spooner 1990, 1991), and 72 genera including 411 species currently are recognized (Hawksworth et al 1995). Only a few species have been reported from China until recently. Since 1990, however, many new members of this order were de- scribed, especially from tropical and subtropical re- gions of China (He et al 1986, Lin and Tang 1988, Hou and Liu 1993, Lin et al 1995, Hou et al 1996, Lin 1998). A total of 11 genera with 80 species were known from China by the end of 2000. Among them 42 species had been described as new to science. As a continuation of this effort the authors made an ex- pedition to Yunnan Province in southwestern China and to Anhui Province in southeastern China in Jul and Aug 2001. Rhododendron species is one of the most important hosts for the members of Rhytismatales. In China