A Review of the Phylogeny and Biology of the Diaporthales
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Mycoscience (2007) 48:135–144 © The Mycological Society of Japan and Springer 2007 DOI 10.1007/s10267-007-0347-7 REVIEW Amy Y. Rossman · David F. Farr · Lisa A. Castlebury A review of the phylogeny and biology of the Diaporthales Received: November 21, 2006 / Accepted: February 11, 2007 Abstract The ascomycete order Diaporthales is reviewed dieback [Apiognomonia quercina (Kleb.) Höhn.], cherry based on recent phylogenetic data that outline the families leaf scorch [A. erythrostoma (Pers.) Höhn.], sycamore can- and integrate related asexual fungi. The order now consists ker [A. veneta (Sacc. & Speg.) Höhn.], and ash anthracnose of nine families, one of which is newly recognized as [Gnomoniella fraxinii Redlin & Stack, anamorph Discula Schizoparmeaceae fam. nov., and two families are recircum- fraxinea (Peck) Redlin & Stack] in the Gnomoniaceae. scribed. Schizoparmeaceae fam. nov., based on the genus Diseases caused by anamorphic members of the Diaportha- Schizoparme with its anamorphic state Pilidella and includ- les include dogwood anthracnose (Discula destructiva ing the related Coniella, is distinguished by the three- Redlin) and butternut canker (Sirococcus clavigignenti- layered ascomatal wall and the basal pad from which the juglandacearum Nair et al.), both solely asexually reproduc- conidiogenous cells originate. Pseudovalsaceae is recog- ing species in the Gnomoniaceae. Species of Cytospora, the nized in a restricted sense, and Sydowiellaceae is circum- anamorphic state of Valsa, in the Valsaceae cause diseases scribed more broadly than originally conceived. Many on Eucalyptus (Adams et al. 2005), as do species of Chryso- species in the Diaporthales are saprobes, although some are porthe and its anamorphic state Chrysoporthella (Gryzen- pathogenic on woody plants such as Cryphonectria parasit- hout et al. 2004, 2005d). Many diseases of crop plants are ica, the cause of chestnut blight, and agricultural crops such caused by members of the Diaporthales. For example, spe- as canker diseases of soybean and sunfl ower caused by cies of Diaporthe-Phomopsis attack sunfl ower and soybean, species of Diaporthe-Phomopsis in both temperate and causing stem cankers and seedling blights (Muntañola- tropical regions. Members of the Diaporthales such as Cvetkovi, et al. 1991; Black et al. 1996). The asexually re- Apiognomonia-Discula and Diaporthe-Phomopsis are com- producing fungus Greeneria uvicola (Berk. & M.A. Curtis) monly encountered as endophytes of woody plants. Punith., cause of bitter rot of grapes, belongs in the Dia- porthales but is not affi liated with any family (Farr et al. Key words Ascomycetes · Canker disease · Endophytes · 2001). Systematics Molecular data support the Diaporthales as a distinct order within the Sordariomycetes, the class including asco- mycetous fungi that produce their asci primarily in perithe- Introduction cial fruiting bodies (Zhang and Blackwell 2001; Castlebury et al. 2003; Zhang et al. 2006). In the latest multigene phy- logeny of this class, the Diaporthales are a well-defi ned or- The ascomycete order Diaporthales includes several plant der in the subclass Sordariomycetidae, most closely related pathogenic fungi, of which the most notorious is the chest- to the Magnaporthaceae and Ophiostomatales and allied nut blight fungus [Cryphonectria parasitica (Murrill) M.E. with the Boliniales, Chaetosphaeriales, Coniochaetales, and Barr] that altered the landscape of eastern North America Sordariales (Zhang et al. 2006). Castlebury et al. (2002) and (Anagnostakis 1988). Numerous other tree diseases are Zhang et al. (2006) suggest that the Magnaporthaceae caused by members of the Diaporthales in either their as- is sister to the Diaporthales. However, recent work by comycetous or asexual states. These diseases include oak Mostert et al. (2006) places the Calosphaeriales even closer to the Diaporthales. According to Kirk et al. (2001), the Diaporthales consists A.Y. Rossman (*) · D.F. Farr · L.A. Castlebury of about 94 genera with 500 species. The anamorphic spe- Systematic Botany and Mycology Laboratory, USDA Agricultural cies derived from within the Diaporthales, including such Research Service, Beltsville, MD 20705, USA + Tel. +1-301-504-5264; Fax +1-301-504-5810 large genera as Cytospora (100 species) and Phomopsis e-mail: [email protected] (100+ species), may at least double the estimated number 136 of species. The Diaporthales are characterized morphologi- The phylogeny of each of the nine families currently cally by brown to black perithecial fruiting bodies immersed recognized in the Diaporthales is reviewed here based on in a stroma or the substrata, lack of true paraphyses at ma- molecular data along with a summary of their biology. For turity, and unitunicate asci that fl oat free within the cen- some families, extensive data exist, while for others very trum at maturity and have a refractive ring in the apex (Barr little is known. Because of the polyphyletic nature of most 1978; Samuels and Blackwell 2001). The known asexual of the genera as defi ned based on morphology, emphasis is states of members of the Diaporthales are generally coelo- placed on type species. At the end of the article, some gen- mycetous, producing phialidic, often annellidic conidioge- era in the Diaporthales are discussed for which data are in- nous cells, and usually non- or one-septate conidia in suffi cient to place them in any existing family. acervuli or pycnidia with or without a well-developed stroma. Gnomoniaceae Figs. 1–4 Generic concepts in the Diaporthales have not been re- evaluated since they were established, primarily on the ba- Members of the Gnomoniaceae occur primarily on hard- sis of the Saccardoan system, which placed high value on wood trees, although other hosts exist, such as conifers for ascospore characters. Characteristics of the stroma and the the anamorph genus Sirococcus. Several diseases are caused anamorph were combined with ascospore characteristics in by species in the Gnomoniaceae, as mentioned below, but the taxonomies proposed by Barr (1978, 1990), Kobayashi these species fruit primarily on overwintered leaves (1970), and Monod (1983; Gnomoniaceae only) that repre- (Stoykow 2005) and are also commonly isolated as endo- sent the most recent monographic accounts of the Dia- phytes (Kaneko and Kobayashi 1984; Barengo et al. 2000). porthales. The few molecular studies in the Diaporthales This family includes at least ten known teleomorphic suggest that these generic concepts must be reevaluated genera, namely, Apiognomonia-Discula, Apioplagiostoma, (Zhang and Blackwell 2001; Castlebury et al. 2002, 2003). Cryptodiaporthe, Cryptosporella-Disculina, Ditopella, In these studies, many of the genera included were deter- Gnomonia, Gnomoniella, Ophiovalsa, Phragmoporthe, and mined to be polyphyletic; thus, placement of the type spe- Plagiostoma, and the anamorphic genus Sirococcus, for cies has been stressed. which no teleomorph is known. Results of molecular studies Although for many years the genera Magnaporthe (Castlebury et al. 2002) generally agree with the concept of and Gaeumannomyces were included in the Diaporthales the Gnomoniaceae as monographed by Monod (1983). (Barr 1978; Yaegashi and Udagawa 1978; Monod 1983; This fi nding differs signifi cantly from other concepts of this Cannon 1988), these genera are now placed in their own family based solely on morphology as proposed by Barr family, Magnaporthaceae (Cannon 1994). In describing (1978, 1990, 1991), Kobayashi (1970), and Vasilyeva this family with six genera, Cannon (1994) reviewed its (1993). ordinal placement and concluded, based primarily on the The Gnomoniaceae is characterized by ascomata that biology of these fungi, that it should be excluded from the are immersed, solitary without a stroma, or aggregated in a Diaporthales. Three recent studies of these taxa using mo- reduced prosenchymatous stroma in herbaceous plant ma- lecular sequence data confi rm the placement of Gaeuman- terial, especially in leaves or stems but also in wood. The nomyces and Magnaporthe outside the Diaporthales (Zhang ascomata are generally soft-textured, thin-walled, and pros- and Blackwell 2001; Castlebury et al. 2002; Zhang et al. enchymatous with either central or lateral beaks. The asci 2006). usually have a distinct apical ring. This family includes spe- Within the Diaporthales, up to eight families have been cies having ascospores that are generally small, less than recognized by various authors over the past 30 years. These 25 µm long, although some are longer as in Cryptosporella, familial classifi cations of the Diaporthales were summa- and range in septation from nonseptate to one-septate or rized by Zhang and Blackwell (2001), comparing Barr multiseptate. The asexual states of members of the Gnomo- (1978, 1990), Kirk et al. (2001), and Wehmeyer (1975). In niaceae are acervular or pycnidial with a broad opening. the most comprehensive molecular study to date, Castle- Conidiogenous cells are phialidic, and conidia are usually bury et al. (2002) analyzed nLSU rDNA sequence data and pallid and nonseptate (Monod 1983). determined that there were six major lineages in the Dia- The genus Gnomonia is represented by the type species porthales. Since then, an additional three lineages have G. gnomon (Tode) J. Schröt. (Sogonov et al. 2005). Species been added such that nine families are now included in the of Gnomonia usually have beaked, thin-walled, solitary order (Rossman et al. 2006). One of these families is named perithecia immersed