A fissitunicate ascus mechanism in the Calosphaeriaceae, and novel species of Jattaea and Calosphaeria on Prunus wood

During a survey of Prunus wood from South Africa, isolations were made of three presumably Calosphaerialean fungi that formed hyphomycetous, phialidic anamorphs in culture. In order to reveal the phylogenetic relationship of these fungi, they were characterised on a morphological and molecular (LSU and ITS rDNA) basis. Two isolates that formed a teleomorph in culture are newly described as Calosphaeria africana sp. nov. Although asci of Calosphaeria are characterised by having non-amyloid apical rings, two functional wall layers were observed in asci of C. africana, which has hitherto not been observed in any member of the Calosphaeriaceae. However, Calosphaeriaceae (Calosphaeriales, Sordariomycetes) are not closely related to other bitunicate fungi like Dothideomycetes, Chaetothyriales and bitunicate lichens. Possession of two separating wall layers is considered to be a result of both inherited abilities and convergent evolution under a strong selection pressure of the environmental conditions that favour an extension of the ascus. The other two species represented a separate lineage within Calosphaeriaceae, and formed phialophora-like anamorphs. By obtaining the teleomorph in culture, one of them could be identified as a species of Jattaea, described here as Jattaea prunicola sp. nov., while the second, which only produced the anamorph, is named as Jattaea mookgoponga sp. nov. These findings suggest that some species of Jattaea are true members of the Calosphaeriaceae, though the phylogenetic relation of the type, J. algeriensis, remains unknown. Furthermore, it also represents the first report of Jattaea on Prunus wood, and from South Africa.