PHYTOPATHOGENIC FILAMENTOUS (ASHBYA, EREMOTHECIUM) AND DIMORPHIC FUNGI (HOLLEYA, NEMATOSPORA) WITH NEEDLE-SHAPED ASCOSPORES AS NEW MEMBERS WITHIN THE SACCHAROMYCETACEAE

Phylogenetic relationships between species from the genera Kluyveromyc es and Saccharomyces and representatives of the Metschnikowiaceae (Hol leya, Metschnikowia, Nematospora) including the two filamentous phytop athogenic fungi Ashbya gossypii and Eremothecium ashbyii were studied by comparing the monosaccharide pattern of purified cell walls, the ub iquinone system, the presence of dityrosine in ascospore walls, and nu cleotide sequences of ribosomal DNA (complete 18S rDNA, ITS1 and ITS2 region). Based on sequence information from both ITS regions, the gene ra Ashbya, Eremothecium, Holleya and Nematospora are closely related a nd may be placed in a single genus as suggested by Kurtzman (1995; J. Industr. Microbiol. 14, 523-530). In a phylogenetic tree derived from the ITS1 and ITS2 region as well as in a tree derived from the complet e 18S rDNA gene, the genus Metschnikowia remains distinct. The molecul ar evidence from ribosomal sequences suggests that morphology and orna mentation of ascospores as well as mycelium formation and fermentation should not be used as differentiating characters in family delimitati on. Our data on cell wall sugars, ubiquinone side chains, dityrosine, and ribosomal DNA sequences support the inclusion of plant pathogenic, predominantly filamentous genera like Ashbya and Eremothecium or dimo rphic genera like Holleya and Nematospora with needle-shaped ascospore s within the family Saccharomycetaceae. After comparison of sequences from the complete genes of the 18S rDNA the genus Kluyveromyces appear s heterogeneous. The type species of the genus, K. polysporus is conge neric with the genus Saccharomyces. The data of Cai et al. (1996; Int. J. Syst. Bacteriol. 46, 542-549) and our own data suggest to conserve the genus Kluyveromyces for a clade containing K, marxianus, K. dobzh anskii, K. wickerhamii and K. aestuarii, which again can be included i n the family Saccharomycetaceae. The phylogenetic age of the Metschnik owiaceae and Saccharomycetaceae will be discussed in the light of coev olution. (C) 1997 by John Wiley & Sons, Ltd.