Coelomycetes is a general term for asexual fungi which includes many important pathogens and species also used in biocontrol, biotechnology and bioremediation. Traditional classification of coelomycetes was based on morphology and was thus subjective, often resulting in artificial generic and species boundaries. Molecular based classification is now available to determine the phylogeny of species and genera. This has revolutionized our understanding of relationships between species and linked genera with their teleomorphs and placed them in a higher taxonomic framework. However, despite such advances approximately only 256 (26%) of the 992 coelomycetous genera are linked to their sexual stage, 105 (11%) are linked to a family or order, while for 631 genera (63%) no linkage is available. In this paper we detail how the taxonomy of coelomycetes has developed, examine some important phytopathogenic genera, and explore their applications.

The Botryosphaeriaceae represents an important, cosmopolitan family of latent pathogens infecting woody plants. Recent studies on native trees in southern Africa have revealed an extensive diversity of species of Botryosphaeriaceae, about half of which have not been previously described. This study adds to this growing body of knowledge, by discovering five new species of the Botryosphaeriaceae on Acacia karroo, a commonly occurring native tree in southern Africa. These species were isolated from both healthy and diseased tissues, suggesting they could be latent pathogens. The isolates were compared to other species for which DNA sequence data are available using phylogenetic analyses based on the ITS, TEF-1α, β-tubulin and LSU gene regions, and characterized based on their morphology. The morphological data were, however, useful to make comparisons with other species found in the same region and on similar hosts. The five new species were described as Diplodia allocellula, Dothiorella dulcispinae, Do. brevicollis, Spencermartinsia pretoriensis and Tiarosporella urbis-rosarum. Evidence emerging from this study suggests that many more species of the Botryosphaeriaceae remain to be discovered in the southern Africa.

Thirty-eight strains of Colletotrichum were isolated from diseased Citrus leaves in Guizhou and Yunnan provinces in China. Based on morphological characters and multilocus sequence data, the strains were identified as C. boninense (1 strain), C. brevispora (1), C. fructicola (2), C. gloeosporioides (29), C. karstii (2), C. simmondsii (1) and Colletotrichum murrayae; the latter represents a new species which is described in this paper. Colletotrichum gloeosporioides was originally isolated from Citrus sinensis in southern Italy and was the most common species associated with diseased leaves of Citrus in China.

During an ongoing study of marine fungi growing on Avicennia marina in the Red Sea coast of Saudi Arabia, a new coelomycete was collected in the genus Amarenographium. The new species is characterized by muriform, brown conidia with one polar gelatinous cap and sheath and holoblastic phialidic conidiogenesis. Amarenographium solium sp. nov. differs from the two known species of Amarenographium by the large size of its pycnidia, a thick (62–75 µm) two-layered peridial wall of the conidiomata that appears as textura epidermoidea in surface view and conidia with one apical appendage. Phylogenetic analysis of SSU and LSU rDNA sequences showed that the new species and thus genus Amarenographium grouped consistently with Medicopsis romeroi with high bootstrap support and form a basal clade to the families: Montagnulaceae and Trematosphaeriaceae, order Pleosporales, Dothideomycetes.

Species of Diaporthe are important phytopathogens with wide host ranges and a global distribution. In the present study multi-locus phylogeny based on combined sequences of rDNA ITS, and partial sequences from the translation elongation factor 1-α (EF 1-α), β tubulin (TUB) and calmodulin (CAL) genes, reveal three new species from fresh collections made in northern Thailand. The new species Diaporthe siamensis, D. thunbergii and D. pterocarpicola are introduced in this paper with full descriptions and comparison with similar taxa. Phomopsis pterocarpi which is epitypified and synonymised under Diaporthe pterocarpi is described based on a collection from northern Thailand.

Specimens of a new Pestalotiopsis species were obtained from leaves of Trachycarpus fortunei from Kunming Botany Garden, Kunming, Yunnan Province, China, where it caused serious leaf blotch and defoliation in the garden. Single ascospore isolates from the teleomorph produced identical colonies with black slimy conidial masses. Morphological characteristics of the conidia produced in culture accorded well with the genus Pestalotiopsis. Based on morphological characters and molecular analysis, Pestalotiopsis trachicarpicola sp. nov. is introduced and both its asexual and sexual forms are described.

A molecular study of selected species of the genera Pseudorobillarda, Robillarda and Xepiculopsis was undertaken to determine their phylogenetic relationships. Based on the analysis of the LSU, SSU and ITS nrDNA, Xepiculopsis graminea belongs in the Hypocreales, grouping with Myrothecium and Didymostilbe (and its sexual morph Peethambara) with species of Stachybotrys in a sister clade, but cannot be assigned to any known family. Robillarda sessillis clusters with members of the Amphisphaeriaceae (Xylariales) but shows no affinity with any genus in that family. Pseudorobillarda species formed a monophyletic group within the Pleosporomycetidae (Dothideomycetes), but do not show affinity with any family or order. This study confirms that Pseudorobillarda and Robillarda are phylogenetically distantly related and a monographic treatment is warranted to resolve the position of other species assigned to these genera. Moreover, molecular data supports the introduction of a new family within the Hypocreales for a well supported clade with the genera Didymostilbe, Myrothecium, Stachybotrys and Xepiculopsis.

Three coelomycetous ascomycetes, Acrocalymma aquatic sp. nov., Aquasubmersa mircensis gen. & sp. nov., and Clohesyomyces aquaticus are reported from northern Thailand. All taxa are characterized, illustrated and subjected to awnalyses of LSU, SSU and/or ITS rDNA gene sequence data to establish their phylogenetic placement in the ascomycetes. Acrocalymma is a monotypic genus in a distinct lineage of Pleosporales which is basal to Morosphaeriaceae as confirmed by our combined SSU and LSU analysis. Acrocalymma aquatica sp. nov., differs in morphology and gene sequence data from other species in the genus. Aquasubmersa mircensis gen. et sp. nov. is phylogenetically unrelated to any other dothideomycetous genus and is introduced as a new genus. Sequence data from Clohesyomyces aquaticus facilitated its accommodation in Lindgomycetaceae.

Colletotrichum species are widely known as key anthracnose pathogens of several economic plants. In this study, Colletotrichum species associated with leaf anthracnose isolated from various plants in Thailand were subjected to morphological and molecular analyses. The ITS rDNA regions of these strains were sequenced and aligned with those of type strains in the genus in order to establish if they can be assigned to any known species. Strains that could not be identified were further sequenced for partial actin (ACT), β-tubulin (TUB2) and glyceraldehydes-3-phosphate dehydrogenase (GAPDH) genes and employed in a phylogenetic analysis to reveal their relationships with other closely related taxa. The multilocus sequence analysis, together with a critical examination of the phenotypic characters, revealed three new species. These are introduced as C. brevisporum, C. tropicicola and C. thailandicum and formally described, illustrated and compared with similar taxa.

Bambusicola, gen. nov., is introduced for four new saprobic taxa from culms of bamboos in northern Thailand. One species, chosen as the generic type, has both sexual and asexual morphs, one species has the sexual morph only and two species have the asexual morph only. The four new species, Bambusicola massarinia, B. bambusae, B. irregulispora and B. splendida are illustrated and described. Isolates of each species were sequenced using LSU, SSU and ITS genes and phylogenetic analysis shows the genus to be a distinct clade in the suborder “Massarineae”. Morphological differences between Bambusicola and some related genera are noted. Bambusicola is characterized by small, cone-shaped ascomata, slightly broad and fusiform ascospores and a coelomycete asexual morph with light brown conidia. Bambusicola clusters in Trematosphaeriaceae, but the closeness of this relationship cannot be resolved.

Coelomycetes are significant fungi, being important plant pathogens responsible for a wide range of diseases worldwide and utilized in industry with some being prolific producers of novel compounds. Morphological identification of genera and species, and species complexes of cryptic taxa is difficult because of the dearth of distinctive morphological characters. With molecular techniques at our disposal we can now begin to understand the phylogeny and complexity of these poorly studied organisms. Large numbers of genera have to be recollected and restudied using molecular techniques. Herbarium material and living cultures must be deposited as a result of future studies and where possible species (and genera) must be epitypified. These efforts will help in the reclassification and phylogeny of the coelomycetes, understanding species complexes and will provide important data for future plant pathology, quarantine and industrial needs.