Mycologia, 100(3), 2008, pp. 417–430. DOI: 10.3852/07-124R2 # 2008 by The Mycological Society of America, Lawrence, KS 66044-8897 Molecular phylogeny of Laetiporus and other brown rot polypore genera in North America Daniel L. Lindner1 Key words: evolution, Fungi, Macrohyporia, Mark T. Banik Polyporaceae, Poria, root rot, sulfur shelf, Wolfiporia U.S.D.A. Forest Service, Madison Field Office of the extensa Northern Research Station, Center for Forest Mycology Research, One Gifford Pinchot Drive, Madison, Wisconsin 53726 INTRODUCTION The genera Laetiporus Murrill, Leptoporus Que´l., Phaeolus (Pat.) Pat., Pycnoporellus Murrill and Wolfi- Abstract: Phylogenetic relationships were investigat- poria Ryvarden & Gilb. contain species that possess ed among North American species of Laetiporus, simple septate hyphae, cause brown rots and produce Leptoporus, Phaeolus, Pycnoporellus and Wolfiporia annual, polyporoid fruiting bodies with hyaline using ITS, nuclear large subunit and mitochondrial spores. These shared morphological and physiologi- small subunit rDNA sequences. Members of these cal characters have been considered important in genera have poroid hymenophores, simple septate traditional polypore taxonomy (e.g. Gilbertson and hyphae and cause brown rots in a variety of substrates. Ryvarden 1986, Gilbertson and Ryvarden 1987, Analyses indicate that Laetiporus and Wolfiporia are Ryvarden 1991). However recent molecular work not monophyletic. All North American Laetiporus indicates that Laetiporus, Phaeolus and Pycnoporellus species formed a well supported monophyletic group fall within the ‘‘Antrodia clade’’ of true polypores (the ‘‘core Laetiporus clade’’ or Laetiporus s.s.) with identified by Hibbett and Donoghue (2001) while the exception of L. persicinus, which showed little Leptoporus and Wolfiporia fall respectively within the affinity for any genus for which sequence data are ‘‘phlebioid’’ and ‘‘core polyporoid’’ clades of true available. Based on data from GenBank, the southern polypores (Binder et al 2005). hemisphere species L. portentosus also fell well Recent molecular and mating studies also have led outside the core Laetiporus clade. Wolfiporia dilatohy- to a revision of genus Laetiporus in North America pha was found to represent a sister group to the core (Banik et al 1998, Banik and Burdsall 1999, Banik and Laetiporus clade. Isolates of Phaeolus, Pycnoporellus Burdsall 2000), which formerly contained only L. and members of the core Laetiporus clade all fell sulphureus (Bull.) Murrill and L. persicinus (Berk & within the Antrodia clade of polypores, while Leptoporus mollis and Laetiporus portentosus fell within M.A. Curtis) Gilbertson. Burdsall and Banik (2001) the phlebioid clade of polypores. Wolfiporia cocos concluded that genus Laetiporus contains at least six isolates also fell in the Antrodia clade, in contrast to morphologically and ecologically distinct species. previous studies that placed W. cocos in the core Despite this recent work relationships remain unre- polyporoid clade. ITS analyses resolved eight clades solved among North American Laetiporus species and within Laetiporus s.s., three of which might represent among other brown rot polyporoid species lacking undescribed species. A combined analysis using the clamps. This study had two goals: (i) to determine three DNA regions resolved five major clades within relationships among North American species of Laetiporus s.s.: a clade containing conifer-inhabiting Laetiporus and (ii) to determine whether any North species (‘‘Conifericola clade’’), a clade containing L. America polyporoid species that cause brown rots and cincinnatus (‘‘Cincinnatus clade’’), a clade contain- lack clamps are closely related to Laetiporus.To ing L. sulphureus s.s. isolates with yellow pores accomplish these goals species of Laetiporus, Lepto- (‘‘Sulphureus clade I’’), a clade containing L. porus, Phaeolus, Pycnoporellus and Wolfiporia were sulphureus s.s. isolates with white pores (‘‘Sulphureus sequenced in three regions of rDNA: the intergenic clade II’’) and a clade containing L. gilbertsonii and transcribed spacer (ITS), the nuclear large subunit unidentified isolates from the Caribbean (‘‘Gilbertso- (nLSU) and the mitochondrial small subunit nii clade’’). Although there is strong support for (mtSSU). groups within the core Laetiporus clade, relationships Of the genera included in this study the most among these groups remain poorly resolved. widely known is Laetiporus. As it is currently defined Laetiporus includes annual polypore species that Accepted for publication 26 February 2008. produce a brown rot, have dimitic binding hyphae 1 Corresponding author. E-mail: [email protected] and lack cystidia and clamp connections (Gilbertson 417 418 MYCOLOGIA and Ryvarden 1986, Ryvarden 1991). With the gilbertsonii occurs in the southern and western regions exception of L. persicinus,allNorthAmerican of North America and occurs on a wide range of Laetiporus species produce brightly colored, conspic- hardwoods including Eucalyptus. The upper pileus uous fruiting bodies that have been regarded tradi- surface of L. gilbertsonii is generally more salmon to tionally as part of the L. sulphureus s.l. species pink than other Laetiporus species while the pore complex. Species in the L. sulphureus s.l. complex layer is either yellow or white, which differentiates the are popular edibles that frequently are collected two color forms, L. gilbertsonii with a yellow pore layer under the common name ‘‘Sulfur Shelf’’ or ‘‘Chicken and L. gilbertsonii var. pallidus with a white pore layer. of the Woods’’ (Arora 1986). Laetiporus sulphureus s.l. Laetiporus persicinus is the one North American also has been investigated for novel antimicrobial and Laetiporus species not considered part of the L. medicinal compounds (Turkoglu et al 2007) and its sulphureus s.l. complex. This is due to striking bright pigments have been examined for potential as macroscopic differences, including a brown to pink- food colorants (Davoli et al 2005). Various authors ish-brown pileus surface, a pinkish-cream pore layer from the late 19th and early 20th centuries described and flesh and tubes that bruise blackish-brown. additional varieties and species within the L. sulphur- Laetiporus persicinus originally was described by eus s.l. complex to account for the wide range of Berkeley and Curtis in 1872 as Polyporus persicinus morphological and ecological variation exhibited by but was transferred to Laetiporus in 1981 by R. this species, although few of these names were used Gilbertson (Gilbertson 1981). Laetiporus persicinus is widely or consistently. Burdsall and Banik (2001) found in the southeastern United States occurring recognize five species and an additional variety within primarily on Quercus although it is found occasionally the L. sulphureus s.l. complex: L. cincinnatus (Mor- on conifers. Burdsall and Banik (2001) hypothesized gan) Burds., Banik & T.J. Volk, L. conifericola Burds. that L. persicinus might not be closely related to & Banik, L. gilbertsonii Burds., L. gilbertsonii var. species in the L. sulphureus s.l. complex based on the pallidus Burds., L. huroniensis Burds. & Banik and L. dark pigmentations in the fruiting bodies, the sulphureus s.s. appearance of the binding hyphae and preliminary With the exception of Laetiporus cincinnatus, all RFLP data. species in the L. sulphureus s.l. complex typically Work by Hibbett and Donoghue (1995) with produce sessile to laterally substipitate pilei with mtSSU rDNA sequences indicated that genus Phaeo- bright orange upper surfaces and yellow or white lus is closely related to Laetiporus sulphureus s.l. This pore layers (Burdsall and Banik 2001). Laetiporus result has been observed in many analyses (Hibbett cincinnatus produces centrally stipitate, rosette- and Donoghue 2001, Hibbett and Binder 2002, shaped fruiting bodies with a white pore layer; these Binder et al 2005), which confirmed that Phaeolus is fruiting bodies arise near the base of large diameter not aligned with the Hymenochaetales despite super- hardwood trees, usually Quercus species, in the ficial similarities (Wagner and Fischer 2001). The eastern and midwestern United States. In North single North American species of Phaeolus treated by America Laetiporus sulphureus s.s. (as defined by Gilbertson and Ryvarden (1987), P. schweinitzii (Fr.) Burdsall and Banik 2001 and the present study) is Pat., is an important root rot pathogen in conifer found in the eastern and midwestern United States ecosystems. Like L. cincinnatus and L. persicinus, P. and often occurs on Quercus species although schweinitzii has a centrally stipitate fruiting body specimens occasionally are found on other hard- found at the base of trees. Unlike Laetiporus species, woods. Preliminary evidence based on a limited it possesses a monomitic hyphal system and produces number of ITS sequences suggests that North hymenial cystidia. Young Phaeolus fruiting bodies are American and European populations of L. sulphureus yellow to orange but become predominantly brown s.s. are conspecific (unpubl data), however further with age (Gilbertson and Ryvarden 1987). comparative work is needed. If species barriers exist Genus Pycnoporellus also contains species with between North American and European populations monomitic, yellow to orange fruiting bodies, leading of L. sulphureus s.s., nomenclatural revision of the Gilbertson and Ryvarden (1987) to suggest a close North American species would be required given that relationship between