Belongs within: Diaporthomycetidae.
Contains: Gnomoniaceae, Cryphonectriaceae, Valsaceae, Diaporthaceae.
The Diaporthales are an order of saprobic and plant-parasitic fungi, usually found on bark and wood (Kirk et al. 2001).
If they only wood
Published 4 October 2009
Most people, when they think of fungi, will think of mushrooms. However, the majority of fungi do not produce such large and obvious structures as mushrooms; the majority of fungi are microscopic decomposers, whose minute fruiting bodies would be easily overlooked by those not looking for them. But tiny as these organisms are, they can have a significant effect on your life.
The Diaporthales are one order of these microfungi. They are a well-defined order of ascomycetes with brown or black perithecia (almost entirely enclosed fruiting bodies with only a single pore at one end and the spores produced inside) submerged either within a stroma (mass of hyphal tissue) or in the surrounding substrate on which they are growing (Rossmann et al. 2007). In many Diaporthales, the opening pore of the perithecia is on a long neck that may or may not also be submerged; it is the combination of round perithecium and elongate neck that lead the authors of one recently-described genus to dub it Lollipopaia (Inderbitzin & Berbee 2001).
Most Diaporthales are decomposers of rotting wood. As such, they rarely come to humanity’s attention, though it probably wouldn’t take us long to notice if they disappeared. A small but significant number of Diaporthales, however, have earned a great deal of attention from humans because, while they grow on wood just like their relatives, they don’t have the courtesy to wait for the tree to die first. The most famous (or notorious, depending on your preferred choice of adjectives) of Diaporthales is undoubtedly Cryphonectria parasitica, the cause of chestnut blight and famed as the bane of the American chestnut, C. dentata. According to Wikipedia, C. dentata may have made up as much as a quarter of the forest in the Appalachian region of eastern North America prior to the arrival of chestnut blight around 1905; by 1940, it was almost extinct. To this day, the position of the American chestnut across most of its original range remains tenuous; complete extinction has been staved off by the chestnut’s ability to produce subsidiary shoots from its base, meaning that a number of trees survive despite being reduced to the central boles. However, complete regrowth is likewise prevented by the fungus attacking any new shoots before they achieve significant growth. Meanwhile, attempts to breed blight-resistant strains of American chestnut are hampered by the tree’s slow growth rate.
When chestnut blight was recorded in European chestnut trees (Castanea sativa) in Italy in 1938, people expected a repeat of the American experience. And at first, that was almost exactly what happened—chestnut blight spread rapidly through western Europe, slowed only by the more scattered distribution of its host (C. sativa was not originally native to most parts of Europe, but introduced by the Romans; as a result, it does not form continuous forests in Europe as C. dentata did in America, but is largely only found where it has been deliberately planted by humans). However, during the 1950s and 1960s, reports started coming in of stands of chestnuts that appeared to be coping surprisingly well despite the obvious presence of blight (Heiniger & Rigling 1994), with the damage from the blight extending only a short way into the wood (as it does in the Asian chestnut Castanea crenata, the original host of the fungus). What was more, when fungal hyphae from these wimpier infections were transplanted into further chestnut trees amongst more normal raging infections, the more virulent infections began to heal. The reduced virulence turns out to be due to a virus infecting the fungus – the disease being cured by a disease of its own. The spread of reduced virulence among chestnut blight in Europe has massively reduced the European epidemic. Attempts to implement the same cure in North America, however, have mostly resulted in failure (Milgroom & Cortesi 2004). Transmission of reduced virulence between fungal colonies is slow and ineffecient, and in most cases seems to require direct human intervention to be truly effective. While this direct intervention is feasible with the more scattered European chestnut, it offers little hope of restoring the prior forests of American chestnut.
Other species of Diaporthales cause diseases in other crop trees and plants (including butternut canker caused by Sirococcus clavigignenti-juglandacearum, which I’m sure is a terrible thing to be afflicted by, even if it does sound like the name of some sort of confectionary). Dogwood anthracnose is caused by Discula destructiva, recently shown to be an anamorphic (asexual) member of the Diaporthales. Cytospora species attack Eucalyptus, while Greeneria uvicola causes bitter rot in grapes. If you feel enticed to explore the systematics and characteristics of the various subgroups of Diaporthales, there’s an impressively detailed coverage on the U.S. Department of Agriculture’s Diaporthales page, including a big interactive tree where clicking on a clade brings up descriptions and images to help you while away the hours.
Bursting through and fading out
Published 21 October 2024
Historically, the classification of fungi was heavily dependent on the description of reproductive features. One collection of hyphae tends to look much like another; fruiting bodies and spores are generally much more distinctive. Unfortunately for the systematic mycologist, however, fungi may produce spores both sexually and asexually, and the structures involved in the two modes of spore formation are very different in appearance. For the most part, those structures produced during sexual reproduction are the more complex, so fungal systematics has tended to focus on them. However, there are many fungi which either do not reproduce sexually or do so only sparingly, and these were the forms known historically as the ‘fungi imperfecti’ or ‘deuteromycetes’.
Asexually produced spores in fungi are referred to as conidia, and the structures on which they develop are known as conidiophores. The basic conidiophore is not much more than a moderately differentiated hyphal branch with conidia often developing as terminal chains. Because the features distinguishing one type of deuteromycete from another were so simple, even early mycologists realised that any attempt to classify them probably represented assemblages of convenience rather than reflecting true evolutionary relationships. Nevertheless, deuteromycetes were typically divided between ‘hyphomycetes’, in which conidiophores arose directly from surrounding hyphae without any clear association into more complex structures, and ‘coelomycetes’, in which some sort of basic ‘fruiting body’ might be distinguished. One such assemblage of ‘coelomycetes’ was recognised as the Melanconiales, in which conidiophores were clustered on the surface of a cushion-like stroma, the stroma and conidiophores together forming a structure known as an ‘acervulus’.
As was noted by Edgerton (1912) in a review of the order’s basic features, the acervulus was clearly developed in response to its producers’ life styles. Melanconiales were parasites on other multicellular organisms: most commonly plants though some might also be found on animals. The hyphae of the growing fungus spread among the cells beneath their host’s outer cuticle, but this layer of epidermis presented a problem when it came time for the fungus to release its spores. A basic conidiophore would be trapped within the host tissue. But if a large number of conidiophores were grouped together, the pressure of them all pushing outwards would be enough to burst through the outer skin, creating a hole in the cuticle through which the conidia could be released.
In modern years, of course, molecular data has come to dominate fungal systematics. And as was predicted by earlier workers such as Edgerton, the imperfect fungi came to be scattered through the family tree. ‘Melanconiales’ could mostly be assigned to the class Sordariomycetes but fell into multiple orders within that class (e.g. Valenzuela-Lopez et al. 2018). Melanconium, the erstwhile type genus of the Melanconiales, refers to forms that may now be assigned to the order Diaporthales. Historically, Melanconium was distinguished by its production of dark, single-celled conidia and growth on the woody branches of trees and shrubs (Edgerton 1912). Sexual forms associated with Melanconium would later be described as Melanconis, under the now-obsolete dual-nomenclature system of referring to sexual and asexual forms of fungi by different names. Because of uncertainty about the identity of Melanconium’s type species, Melanconis has been preferred as the genus’ name in recent years. Matters are not helped by the fact that Melanconis species produce more than one type of conidium: when their acervuli first develop, they produce dark ‘Melanconium’-type spores, but later on they produce narrow, paler spores that would have once been described as a different imperfect genus (Jaklitsch & Voglmayr 2020). Melanconium is thus no longer used as a formal genus (though ‘melanconium’ may be used to refer to a type of spore), and it has pulled the ‘Melanconiales’ down with it.
Systematics of Diaporthales
Characters (Kirk et al. 2001): Ascomata perithecial, usually aggregated into pseudostroma, usually long-necked. Interascal tissue absent or of thin-walled unspecialised cells, deliquescing early. Asci usually thick-walled but not fissitunicate, with conspicuous J- refractive apical ring. Ascospores very varied. Anamorphs varied, coelomycetous.
Diaporthales [Melanconiales, Valsales]
|--Pseudovalsa Ces. & De Not. 1863HM17, KC01 (see below for synonymy)
| | i. s.: *P. lanciformis (Fr.) Ces. & De Not. 1863 (see below for synonymy)RA15
| | P. berkeleyiRS99
| | ‘Coryneum’ foliicolumM27
| | ‘Coryneum’ microstictumM27
| | ‘Coryneum’ ruborumM27
| |--P. umbonataHM17 [=*Coryneum umbonatum Nees 1816RA15]
| `--+--P. longipesHM17
| |--P. modoniaHM17
| `--Tirisporellaceae [Tirisporellales]HM17
| |--Tirisporella Jones, Hyde & Alias 1996KC01
| | `--T. beccarianaHM17
| `--Thailandiomyces bisetulosusHM17
`--+--+--Pseudoplagiostoma [Pseudoplagiostomataceae]HM17
| | |--P. corymbiaeHM17
| | `--P. eucalyptiHM17
| `--StilbosporaceaeHM17
| |--Stilbospora Pers. 1794RA15 (see below for synonymy)
| | |--*S. macrosperma Pers. 1801 [incl. *Prosthecium ellipsosporum Fresen. 1852]RA15
| | `--S. longicornutaHM17
| `--Stegonsporium Corda 1827HM17, KC01
| |--S. protopyriformeHM17
| `--S. pyriformeHM17
`--+--+--+--GnomoniaceaeHM17
| | `--Gnomoniella Sacc. 1881LK04, KC01 (see below for synonymy)
| | `--G. fraxiniLK04
| `--+--Harknessia Cooke 1881HM17, KC01 [incl. Caudosporella Höhn. 1914KC01, Mastigonetron Kleb. 1914KC01; Harknessiaceae]
| | |--H. eucalyptiHM17
| | `--H. weresubiaeHM17
| `--+--CryphonectriaceaeHM17
| `--Pilidiella Petr. & Syd. 1927 (nom. cons.)HM17, KC01 (see below for synonymy)
| | i. s.: *P. quercicola (Oudem.) Petr. 1927 [=Macroplodia quercicola Oudem. 1902]RA15
| | P. angustispora (Samuels et al.) Rossman & Crous in Rossman, Adams et al. 2015 (see below for synonymy)RA15
| | P. calamicola (Fröhl. & Hyde) Rossman & Crous in Rossman, Adams et al. 2015 (see below for synonymy)RA15
| | P. castaneicola (Ellis & Everh.) Arx 1957 [=Gloeosporium castaneicola Ellis & Everh. 1895]RA15
| | P. granatiRA15
| | P. pseudogranati (Crous) Rossman & Crous in Rossman, Adams et al. 2015 (see below for synonymy)RA15
| | P. stromatica (Samuels et al.) Rossman & Crous in Rossman, Adams et al. 2015 (see below for synonymy)RA15
| | P. terminaliae (Samuels et al.) Rossman & Crous in Rossman, Adams et al. 2015 (see below for synonymy)RA15
| | P. tibouchinaeRA15
| |--P. wangiensisHM17
| `--+--P. diplodiellaHM17
| `--P. stramineaHM17 [=*Schizoparme straminea Shear 1923RA15; incl. Nectriella versonianaRS99]
`--+--+--ValsaceaeHM17
| `--+--DiaporthaceaeHM17
| `--Macrohilum Swart 1988HM17, KC01 [Macrohilaceae]
| `--M. eucalyptiHM17
`--+--LamproconiaceaeHM17
| |--Lamproconium (Grove) Grove 1937KC01
| | `--*L. desmazieriHM17
| `--Hercospora Fr. 1825HM17, KC01 [incl. Galeraicta Preuss 1852KC01, Rabenhorstia Fr. 1849KC01]
| `--H. tiliaeHM17
`--SydowiellaceaeHM17
| i. s.: Sydowiella Petr. 1923KC01
|--Hapalocystis Auersw. ex Fuckel 1863HM17, KC01
| `--H. occidentalisHM17
`--+--Rossmania ukurunduensisHM17
`--Sillia Karst. 1873HM17, KC01
`--S. ferrugineaHM17
Diaporthales incertae sedis:
Anisomycopsis Hino & Katum. 1964KC01
Cryptoleptosphaeria Petrak 1923EB03, RS99 [=Cryptopeltosphaeria (l. c.)RS99]
|--*C. moravica Petrak 1923 [=Cryptopeltosphaeria (l. c.) moravica]RS99
`--C. gracilis (Munk) Rossman & Samuels in Rossman, Samuels et al. 1999 [=Debaryella gracilis Munk 1954]RS99
Cryptonectriella (von Höhnel) Weese 1919EB03, RS99 [=Nectriella sect. Cryptonectriella von Höhnel 1918RS99]
|--*C. biparasitica (von Höhnel) Weese 1919 (see below for synonymy)RS99
`--C. geoglossi (van Overeem) Lowen in Rossman, Samuels et al. 1999 [=Nectriella geoglossi van Overeem 1923]RS99
Exormatostoma Gray 1821 (n. d.)KC01
Keinstirschia Reid & Booth 1989KC01
Pedumispora Hyde & Jones 1992KC01
Pseudocryptosporella Reid & Booth 1969KC01
Pseudothis Theiss. & Syd. 1914KC01
`--P. cingulata Sydow & Sydow 1916SS16
Savulescua Petr. 1959KC01
Sphaerognomoniella Naumov & Kusnezowa 1952KC01
Stioclettia Dennis 1975KC01
Trematovalsa Jacobesco 1906KC01
Debaryella von Höhnel 1904 (n. d.)RS99
`--*D. hyalina von Höhnel 1904 (n. d.)RS99
Juglanconis Voglmayr et al. 2017 [Juglanconidaceae, Melansporellaceae]HM17
Amphilogia gyrosaSS09
Caudospora Starbäck 1889KC01
Valsaria Ces. & De Not. 1863KC01 (see below for synonymy)
`--V. rubricosa (see below for synonymy)RS99
*Cryptonectriella biparasitica (von Höhnel) Weese 1919 [=Charonectria biparasitica von Höhnel 1903, Nectriella biparasitica (von Höhnel) Weese 1914; incl. Debaryella vexans von Höhnel 1906]RS99
Gnomoniella Sacc. 1881LK04, KC01 [incl. Frankia Brunch. 1886KC01, Frankiella Speschnew 1900KC01, Greeneria Scribn. & Viala 1887KC01]
Pilidiella Petr. & Syd. 1927 (nom. cons.)HM17, KC01 [incl. Anthasthoopa Subram. & Ramakr. 1956KC01, Baeumleria Petr. & Syd. 1927KC01, Coniella Höhn. 1918KC01, Cyclodomella Mathur., Bhatt & Thirum. 1959KC01, Embolidium Bat. 1964 non Sacc. 1878KC01, Schizoparme Shear 1923RA15; SchizoparmaceaeHM17]
Pilidiella angustispora (Samuels et al.) Rossman & Crous in Rossman, Adams et al. 2015 [=Schizoparme angustispora Samuels et al. 1993]RA15
Pilidiella calamicola (Fröhl. & Hyde) Rossman & Crous in Rossman, Adams et al. 2015 [=Schizoparme calamicola Fröhl. & Hyde 2000]RA15
Pilidiella pseudogranati (Crous) Rossman & Crous in Rossman, Adams et al. 2015 [=Schizoparme pseudogranati Crous 2014]RA15
Pilidiella stromatica (Samuels et al.) Rossman & Crous in Rossman, Adams et al. 2015 [=Schizoparme stromatica Samuels et al. 1993]RA15
Pilidiella terminaliae (Samuels et al.) Rossman & Crous in Rossman, Adams et al. 2015 [=Schizoparme terminaliae Samuels et al. 1993]RA15
Pseudovalsa Ces. & De Not. 1863HM17, KC01 [incl. Coryneum Nees 1816KC01, Murogenella Goos & Morris 1965KC01, Oostroma Bonord. 1864KC01; PseudovalsaceaeHM17]
*Pseudovalsa lanciformis (Fr.) Ces. & De Not. 1863 [=Sphaeria lanciformis Fr. 1818, Coryneum lanciforme (Fr.) Voglmayr & Jaklitsch in Rossman, Adams et al. 2015; incl. C. brachyurum Link in Willdenow 1825]RA15
Stilbospora Pers. 1794RA15 [incl. Calospora Sacc. 1883 non Nitschke ex Niessl 1875KC01, Calosporella Schröt. 1897KC01, Janospora (Starbäck) Höhn. 1923KC01, Phaeodiaporthe Petr. 1920KC01, Prosthecium Fresen. 1852RA15]
Valsaria Ces. & De Not. 1863KC01 [incl. Hypoxylonopsis Henn. 1904KC01, Phaeocreopsis Saccardo & Sydow in Lindau 1900RS99, Phaeosperma (Sacc.) Traverso 1906 nec Nitschke ex Otth 1869 nec Nitschke ex Fuckel 1870KC01, Pseudothyridaria Petr. 1925KC01; Valsariales]
Valsaria rubricosa [incl. Valsaria cinnamomi, Valsonectria cinnamomi, Hypocreopsis hypoxyloides Spegazzini 1899, *Phaeocreopsis hypoxyloides (Spegazzini) Saccardo & Sydow in Lindau 1900, Valsaria hypoxyloides, Valsonectria hypoxyloides, P. pezizaeformis, Hypocreopsis pezizaeformis, Valsonectria reticulata]RS99
*Type species of generic name indicated
References
Edgerton, C. W. 1912. The Melanconiales. Transactions of the American Microscopical Society 31 (4): 243–265.
Ellison, A. M., M. S. Bank, B. D. Clinton, E. A. Colburn, K. Elliott, C. R. Ford, D. R. Foster, B. D. Kloeppel, J. D. Knoepp, G. M. Lovett, J. Mohan, D. A. Orwig, N. L. Rodenhouse, W. V. Sobczak, K. A. Stinson, J. K. Stone, C. M. Swan, J. Thompson, B. Von Holle & J. R. Webster. 2005. Loss of foundation species: consequences for the structure and dynamics of forested ecosystems. Frontiers in Ecology and the Environment 3 (9): 479–486.
[EB03] Eriksson, O. E., H. O. Barah, R. S. Currah, K. Hansen, C. P. Kurtzman, G. Rambold & T. Laessøe (eds.) 2003. Outline of Ascomycota—2003. Myconet 9: 1–89.
Heiniger, U., & D. Rigling. 1994. Biological control of chestnut blight in Europe. Annual Review of Phytopathology 32: 581–599.
[HM17] Hongsanan, S., S. S. N. Maharachchikumbura, K. D. Hyde, M. C. Samarakoon, R. Jeewon, Q. Zhao, A. M. Al-Sadi & A. H. Bahkali. 2017. An updated phylogeny of Sordariomycetes based on phylogenetic and molecular clock evidence. Fungal Diversity 84: 25–41.
Inderbitzin, P., & M. L. Berbee. 2001. Lollipopaia minuta from Thailand, a new genus and species of the Diaporthales (Ascomycetes, Fungi) based on morphological and molecular data. Canadian Journal of Botany 79: 1099–1106.
Jaklitsch, W. M., & H. Voglmayr. 2020. The genus Melanconis (Diaporthales). MycoKeys 63: 69–117.
[KC01] Kirk, P. M., P. F. Cannon, J. C. David & J. A. Stalpers. 2001. Ainsworth & Bisby’s Dictionary of the Fungi 9th ed. CAB International: Wallingford (UK).
[LK04] Lutzoni, F., F. Kauff, C. J. Cox, D. McLaughlin, G. Celio, B. Dentinger, M. Padamsee, D. Hibbett, T. Y. James, E. Baloch, M. Grube, V. Reeb, V. Hofstetter, C. Schoch, A. E. Arnold, J. Miadlikowska, J. Spatafora, D. Johnson, S. Hambleton, M. Crockett, R. Shoemaker, G.-H. Sung, R. Lücking, T. Lumbsch, K. O’Donnell, M. Binder, P. Diederich, D. Ertz, C. Gueidan, K. Hansen, R. C. Harris, K. Hosaka, Y.-W. Lim, B. Matheny, H. Nishida, D. Pfister, J. Rogers, A. Rossman, I. Schmitt, H. Sipman, J. Stone, J. Sugiyama, R. Yahr & R. Vilgalys. 2004. Assembling the fungal tree of life: progress, classification, and evolution of subcellular traits. American Journal of Botany 91 (10): 1446–1480.
Milgroom, M. G., & P. Cortesi. 2004. Biological control of chestnut blight with hypovirulence: a critical analysis. Annual Review of Phytopathology 42: 311–338.
[M27] Murray, B. J. 1927. Four fungi on the endemic species of Rubus in New Zealand. Transactions and Proceedings of the New Zealand Institute 57: 218–225.
[RA15] Rossman, A. Y., G. C. Adams, P. F. Cannon, L. A. Castlebury, P. W. Crous, M. Gryzenhout, W. M. Jaklitsch, L. C. Mejia, D. Stoykov, D. Udayanga, H. Voglmayr & D. M. Walker. 2015. Recommendations of generic names in Diaporthales competing for protection or use. IMA Fungus 6 (1): 145–154.
Rossmann, A. Y., D. F. Farr & L. A. Castlebury. 2007. A review of the phylogeny and biology of the Diaporthales. Mycoscience 48: 135–144.
[RS99] Rossman, A. Y., G. J. Samuels, C. T. Rogerson & R. Lowen. 1999. Genera of Bionectriaceae, Hypocreaceae and Nectriaceae (Hypocreales, Ascomycetes). Studies in Mycology 42: 1–248.
[SS09] Schoch, C. L., G.-H. Sung, F. López-Giráldez, J. P. Townsend, J. Miadlikowska, V. Hofstetter, B. Robbertse, P. B. Matheny, F. Kauff, Z. Wang, C. Gueidan, R. M. Andrie, K. Trippe, L. M. Ciufetti, A. Wynns, E. Fraker, B. P. Hodkinson, G. Bonito, J. Z. Groenewald, M. Arzanlou, G. S. de Hoog, P. W. Crous, D. Hewitt, D. H. Pfister, K. Peterson, M. Gryzenhout, M. J. Wingfield, A. Aptroot, S.-O. Suh, M. Blackwell, D. M. Hillis, G. W. Griffith, L. A. Castlebury, A. Y. Rossman, H. T. Lumbsch, R. Lücking, B. Büdel, A. Rauhut, P. Diederich, D. Ertz, D. M. Geiser, K. Hosaka, P. Inderbitzin, J. Kohlmeyer, B. Volkmann-Kohlmeyer, L. Mostert, K. O’Donnell, H. Sipman, J. D. Rogers, R. A. Shoemaker, J. Sugiyama, R. C. Summerbell, W. Untereiner, P. R. Johnston, S. Stenroos, A. Zuccaro, P. S. Dyer, P. D. Crittenden, M. S. Cole, K. Hansen, J. M. Trappe, R. Yahr, F. Lutzoni & J. W. Spatafora. 2009. The Ascomycota tree of life: a phylum-wide phylogeny clarifies the origin and evolution of fundamental reproductive and ecological traits. Systematic Biology 58 (2): 224–239.
[SS16] Sydow, H., & P. Sydow. 1916. Fungi papuani. Die von C. Ledermann in Neu-Guinea gesammelten Pilze. Botanische Jahrbücher für Systematik, Pflanzengeschichte und Pflanzengeographie 54: 246–261.
Valenzuela-Lopez, N., J. F. Cano-Lira, A. M. Stchigel & J. Guarro. 2018. DNA sequencing to clarify the taxonomical conundrum of the clinical coelomycetes. Mycoses 61: 708–717.