On the subdivision of Ceratocystis s.l., based on partial ribosomal DNA sequences G. HAUSNER AND J. REID' Department of Botany, Universio of Manitoba, Winnipeg, Man., Canada R3T 2N2 AND G. R. KLASSEN Department of Microbiology, Universio of Manitoba, Winnipeg, Man., Canada R3T 2N2 Received July 2 1, 1992 HAUSNER, G., REID, J., and KLASSEN, G. R. 1993. On the subdivision of Ceratocystis s.l., based on partial ribosomal DNA sequences. Can. J. Bot. 71: 52 -63. Analyses of partial rDNA sequences from both the small and large subunit genes of species of Ceratocystis s.1. support the contention that species that lack Chalara anamorphs, are resistant to cycloheximide, and have rhamnose in their cell walls should be assigned to Ophiostoma, whereas only species with Chalara anamorphs should be accommodated in Ceratocystis s.s. The data also show that Ceratocystiopsis is polyphyletic, and Sphaerorlaetr~ella fimicola appears to have little relation to either Ceratocystis or Ophiostoma. Key words: Ceratocystis, Ophiostorna, phylogeny, partial rDNA sequences. HAUSNER, G., REID, J., et KLASSEN, G. R. 1993. On the subdivision of Ceratocystis s.l., based on partial ribosomal DNA sequences. Can. J. Bot. 71 : 52-63. Les auteurs ont analysC les sequences partielles ii la fois des petites et des grandes sous-unit6 du rADN chez des espkces de Ceratocystis s.1.; les risultats de ces analyses supportent l'idee que les espkces qui ne posskdent pas d'anamorphe du type Chalara, qui sont resistantes ii la cyclohexirnide, et qui cornportent du rhamnose dans leur paroi devraient &treplacCes dins le groupe Ceratocystis s.s. Les donnCes montrent Cgalernent que le taxon Ceratocystiopsis est polyphyletique et que le Sphaerot~aemella fimicola ne semble avoir que peu de relations avec Ceratocystis ou Ophiostoma. Mots elks : Ceratocystis, Ophiostotna, phylogCnie, sequences partielles du rADN. [Traduit par la rkdaction] Introduction The disposition of the genus Ceratocystis Ell. & Halst. s.1. within the Ascomycotina is unresolved; additionally its sub- division into smaller groups has long been a source of con- troversy. De Hoog and Scheffer (1984) placed species of Ceratocystis s.1. that lack Chalara anamorphs, are resistant to cycloheximide, and have rhamnose in their cell walls in Ophiostoma H. & P. Sydow, while they assigned those with Chalara anamorphs to Ceratocystis s.s. Moreover, de Hoog and Scheffer (1984) also recognized Ceratocystiopsis, a genus erected by Upadhyay and Kendrick (1975) to accommodate species of Ceratocystis s.1. that produce elongate or falcate- type ascospores. Von Arx and van der Walt (1987) also accepted three genera in the Ophiostomataceae, Ophiostoma, Ceratocystiopsis, and Europhium Parker, but placed Cer- morphs and are biologically heterogenous when compared with those of the Ophiostoma complex (Harrington 1987). Ceratocystis s.s. includes temperate and tropical species that grow on a wide variety of herbaceous and woody plants, whereas most Ophiostoma species are found in the woody xylem or phloem of temperate forest trees. Ophiostoma spe- cies are primarily vectored by subcortical insects such as bark beetles; in contrast, species of Ceratocystis s.s. also have flies and sapfeeding insects as important agents of spore dispersal. As pathogens, the following species of Ceratocystis s.s. may be of great economic importance: Ceratocystis fimbriata Ell. & Halst. causes rot in sweet potatoes and wilt of coffee and rubber trees; Ceratocystis paradoxa (Dade) C. Moreau causes diseases in palms and sugar cane; Ceratocystis adiposa (Butl.) C. Moreau causes black rot of sugar cane; Ceratocystis atocystis s.s. in the ~~xidio~horaceae Arnold in their poly- fagacearum (Bretz.) Hunt causes oak wilt; and Ceratocystis phyletic concept of the Ophiostomatales. Upadhyay (1981) coerulescens (Miinch) Bakshi causes maple sapstreak. considered Europhium to be a synonym of Ceratocystis s.1. To obtain additional evidence that species assigned to Cer- whereas Benny and Kimbrough (1980) and Harrington (1987) atocystis s.s. constitute a valid genus, partial ribosomal DNA placed Europhium in synonymy with Ophiostoma. Recently (rDNA) sequences were determined from the large subunit Barr (1990) followed von Arx and van der Walt's (1987) nar- gene (LSrRNA). Also, partial rDNA sequences were collected row circumscription of the Ophiostomataceae, but she assigned from the small ribosomal subunit gene (SSrRNA) of two Ceratocystis s.s. to the Lasiosphaeriaceae (Sordariales) and members of Ceratocystis s.s. (C. fimbriata, Ceratocystis aligned the Ophiostomataceae with the Microascaceae in the moniliformis (Hedgc.) C. Moreau) and other species included Microascales. In addition to the foregoing, we recently used analysis of partial rDNA sequences to show that Europhium species are closely related to Ophiostoma species (Hausner et al. 19926). This strongly supports those who believe Europhium should be reduced to synonymy with Ophiostoma. De Hoog (1974) recognized only 11 species of Ceratocystis s.s., these have Chalara, Chalaropsis or Thielaviopsis ana- 'Author to whom all correspondence should be addressed. Primed in Canada I lrn~rirni au Canada within the ~~hiostomataceae to gain a better understanding of the taxonomic disposition of Ceratocystis s.s. within the Asco- mycotina. The advantages of analyzing rRNA and (or) rDNA sequences for phylogenetic studies were discussed previously (Kurtzman 1992; Cedergreen et al. 1988; Sogin et al. 1986a; Hillis and Dixon 199 1 ; Woese 1987), and partial or complete rDNA and (or) rRNA sequences were used to assess rela- tionships among a large variety of fungi (GuCho et al. 1990; Guadet et al. 1989; Bruns ef 1989; Berbee and Taylor 1992a, 19926; Bowman et al. 1992).