Diaporthales

Pseudovalsa longipes, copyright Tobias Bøllingtoft.

Belongs within: Diaporthomycetidae.
Contains: Gnomoniaceae, Cryphonectriaceae, Valsaceae, Diaporthaceae.

If they only wood
Published 4 October 2009
Perithecia (fruiting bodies) of Cryphonectria cubensis, the cause of eucalyptus canker. Photo by Edward Barnard.

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).

Pycnidia of Cryphonectria parasitica protruding from chestnut bark. Pycnidia resemble perithecia, but differ in containing asexually- rather than sexually-produced spores. Photo from here.

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.

Three views of American chestnut (Castanea dentata). On the left, American chestnut trees as they could still be found in 1910. In the centre, American chestnut as it survives today—an understorey regenerating shrub, prevented from reaching full growth by the inevitable onset of blight. On the right, the intermediary stage in a grown chestnut felled by the fungus. Images from Ellison et al. (2005).

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.

Systematics of Diaporthales
Diaporthales [Melanconiales, Valsales]
|--Pseudovalsa Ces. & De Not. 1863HM17, KC01 (see below for synonymy)
| | i. s.: P. berkeleyiRS99
| | 'Coryneum’ foliicolumM27
| | 'Coryneum’ microstictumM27
| | 'Coryneum’ ruborumM27
| |--P. umbonataHM17
| `--+--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. 1797 [incl. Janospora (Starbäck) Höhn. 1923]KC01
| | `--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 (see below for synonymy)
| | |--H. eucalyptiHM17
| | `--H. weresubiaeHM17
| `--+--CryphonectriaceaeHM17
| `--SchizoparmaceaeHM17
| |--Schizoparme Shear 1923RS99 (see below for synonymy)
| | `--*S. straminea Shear 1923 [incl. Nectriella versoniana]RS99
| `--Pilidiella Petr. & Syd. 1927HM17, KC01
| |--P. wangiensisHM17
| `--+--P. diplodiellaHM17
| `--P. stramineaHM17
`--+--+--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 (see below for synonymy)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 (see below for synonymy)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

Cryptoleptosphaeria gracilis (Munk) Rossman & Samuels in Rossman, Samuels et al. 1999 [=Debaryella gracilis Munk 1954]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

Cryptonectriella geoglossi (van Overeem) Lowen in Rossman, Samuels et al. 1999 [=Nectriella geoglossi van Overeem 1923]RS99

Gnomoniella Sacc. 1881LK04, KC01 [incl. Frankia Brunch. 1886KC01, Frankiella Speschnew 1900KC01, Greeneria Scribn. & Viala 1887KC01]

Harknessia Cooke 1881HM17, KC01 [incl. Caudosporella Höhn. 1914KC01, Mastigonetron Kleb. 1914KC01; Harknessiaceae]

Pseudovalsa Ces. & De Not. 1863HM17, KC01 [incl. Coryneum Nees 1816KC01, Murogenella Goos & Morris 1965KC01, Oostroma Bonord. 1864KC01; PseudovalsaceaeHM17]

Schizoparme Shear 1923RS99 [incl. Anthasthoopa Subram. & Ramakr. 1956KC01, Baeumleria Petr. & Syd. 1927KC01, Coniella Höhn. 1918KC01, Cyclodomella Mathur., Bhatt & Thirum. 1959KC01, Embolidium Bat. 1964 non Sacc. 1878KC01]

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

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.

[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.

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.

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