By Thomas Læssøe

 

This family of mostly distinctly stromatic pyrenomycetes is grossly underworked in Africa, including Burkina Faso and adjacent areas (Læssøe & al. 1996). After the excellent papers by Dennis (1958, 1961, 1962, 1963, 1964) based mainly on the classic Congo material collected by the Belgians, the subject has hardly been touched upon.

An exemption or two can be mentioned. Hawksworth (1977) studied and described the genus Rhopalostroma and Taligola & Whalley did some preliminary work on Ugandan Hypoxylon species (Taligola & Whalley, 1976, 1977, Whalley & Taligola 1976, Whalley, Hammelev & Taligola 1988). Martins papers (1967, 1968a,b, 1969a,b,c & 1970) partly based on South- African material clearly also deserves a mention.

This limited publication record is not because of lack of promise in such a study. Dennis' papers are full of new and exciting taxa, and it is clear that much remains to be done. Studies made in other tropical regions have shown a very high diversity in the family. Furthermore, the ecological niches species of the family occupy constitute a very wide range, including desert-like habitats, where fx species of Xylaria may be associated with underground plant structures or with termitaria. Most species are thought to be saprotrophic but a range of species in fx the genus Rosellinia are considered serious crop pathogens (fx on coffee). The highest diversity is probably to be expected in the rain forest regions. It is well known that many species in diverse genera of the Xylariaceae can be isolated from living, seemingly healthy plant tissues, and they may in some cases be very important endophytes. Some species always develop stromata on newly dead substrate whilst others always produce these structures on strongly decayed timber. How host specific various species are, is a question yet to be answered but it is clear that at least some are highly host specific. Currently more than 40 genera are recognized, some of which yet has to be discovered in Africa.

In the microscope most members of the family can be recognized by having: 1) dark unicelluar spores with more or less evident germination sites, mostly in the form of a slit (pale line). In some cases the immature spores are bicellular and may leave a cellular appendage on the mature spore. Some have gel-coats or appendages; 2) a mostly blue reaction to the apical apparatus of the asci in iodine reagents.

Anamorphs feature prominently in the life cycle and can mostly be referred to hyphomycetes belonging to Nodulisporium/Geniculisporium and similar forms. They can form freely, on coremia or on stromata. Some Xylaria species produce sclerotia.

Xylaria

Hypoxylon

Rosellinia

Poronia

Podosordaria

Daldinia

 

 

 

References

Dennis, R.W.G. 1958. Some Xylosphaeras of tropical Africa. Revista de Biologia 1(3-4): 175-208.

Dennis, R.W.G. 1959. Further notes on tropical American Xylariaceae. Kew Bulletin 12(2): 297-332.

Dennis, R.W.G. 1961. Xylarioideae and Thamnomycetoideae of Congo. Bulletin du Jardin Botanique de l'État, Bruxelles 31: 109-154.

Dennis, R.W.G. 1962. Flore iconographique des champignons du Congo. 11e fasc. Xylarioideae et Thamnomycetoideae. Bruxelles

Dennis, R.W.G. 1963. Hypoxyloideae of Congo. Bulletin du Jardin Botanique de l'État, Bruxelles 33(3): 317-343.

Dennis, R.G.G. 1964. Further records of Congo Xylariaceae. Bulletin du Jardin Botanique de l'État, Bruxelles 34(2): 231-241.

Hawksworth, D.L. 1977. Rhopalostroma, a new genus in the Xylariaceae s.l. Kew Bulletin 31(3): 421-431.

Ju, Y.-M. & Rogers, J.D. 1996. A revision of the genus Hypoxylon. Mycologia Memoir 20, 365 pp. APS Press, St. Paul, Minnesota.

Ju, Y.-M., Rogers, J.D. & San Martín, F.1997. A revision of the genus Daldinia. Mycotaxon 61: 243-293.

Læssøe, T., Ryvarden, L., Watling, R. & Whalley, A.J.S. 1996. Saprotrophic fungi of the Guinea-Congo region. In:

Alexander, Swaine & Watling (eds.): Essays on the ecology of the Guinea-Congo rain forest. - Royal Society of Edinburgh, Proceedings Sect. B104: 335-348.

Martin, P. 1967. Studies in the Xylariaceae: II. Rosellinia and the Primo-cinerea section of Hypoxylon. Journal of South African Botany 33(4): 315-328.

Martin, P. 1968a. Studies in the Xylariaceae: III. South African and foreign species of Hypoxylon sect. Entoleuca. Journal of South African Botany 34(3): 153-199.

Martin, P. 1968b. Studies in the Xylariaceae: IV. Hypoxylon, sections Papillata and Annulata. Journal of South African Botany 34(5): 303-330.

Martin, P. 1969a. Studies in the Xylariaceae: V. Euhypoxylon. Journal of South African Botany 35(3): 149-206.

Martin, P. 1969b. Studies in the Xylariaceae: VI. Daldinia, Numulariola and their allies. Journal of South African Botany 35(4): 267-320.

Martin, P. 1969c. Studies in the Xylariaceae: VII. Anthostomella and Lopadostoma. Journal of South African Botany 35(6): 393-410.

Martin, P. 1970. Studies in the Xylariaceae: VIII. Xylaria and its allies. Journal of South African Botany 36(2): 73-138.

Rogers, J.D., Ju, Y.-M. & Hemmes, D.E. 1992. Hypoxylon rectangulosporum sp.nov., Xylaria psidii sp.nov., and comments on taxa of Podosordaria and Stromatoneurospora. Mycologia 84(2): 166-172.

Taligoola, H.K. & Whalley, A.J.S. 1976. The genus Hypoxylon in Uganda forests. Transactions of the British mycological Society 67(3): 517-519.

Taligoola, H.K. & Whalley, A.J.S. 1977. Hypoxylon megaannulatum sp.nov. A new species of Hypoxylon from Uganda. Transactions of the British mycological Society 68: 298-300.

Whalley, A.J.S., Hammelev, D. & Taligoola, H.K. 1988. Two new species of Hypoxylon from Nigeria. Transactions of the British mycological Society 90(1): 39-141.

Whalley, A.J.S. & Taligoola, H.K. 1976. Species of Hypoxylon from Uganda. The Transactions and Proceedings of the Botanical Society of Ediburgh 42 (supplement): 93-98.