Ophiostoma quercus is a morphologically variable species that causes sapstain on mostly hardwood hosts worldwide. Several species have been suggested as synonyms of O. quercus in the past, including O. fagi, O. roboris, O. valachicum, O. kubanicum, and O. catonianum. A recent collection of isolates resembling O. quercus from Azerbaijan provided the opportunity to reconsider the accuracy of these synonymies based on morphology and DNA sequence data. Four gene regions, the ribosomal internal transcribed spacer regions including the 5.8 s gene, part of the β-tubulin gene, translation elongation factor-1α, and histone gene, were used to determine the phylogenetic relationships between the various species and isolates of different origin. In all four resulting phylogenetic trees, isolates of O. quercus, O. fagi, and O. roboris formed a single, well-supported cluster, but with some internal variation. All the other species in the analyses, including O. piceae and O. catonianum, grouped distinctly with good node support. These results thus support the synonymy of O. fagi and O. roboris with O. quercus, and confirm that O. piceae and O. catonianum are distinct taxa. Ophiostoma valachicum and O. kubanicum could not be considered due to the absence of cultures, but based on published descriptions, we argue that O. valachicum should be regarded as a valid species in need of neotypification. Ophiostoma kubanicum was never validly described and should be excluded from the list of synonyms of O. quercus.

Polymorphic sequence-characterised marker assays from a recent diversity study on the Ascomycete fungus Ophiostoma quercus reported that some isolates from Africa were genetically distinct from O. quercus. In the present study, these African isolates were compared with authentic O. quercus isolates by evaluating morphological characters, growth in culture, mating compatibility and DNA sequence data. The isolates from Africa were morphologically similar to O. quercus, presenting Pesotum and Sporothrix synanamorphs in culture. Phylogenetic analyses of the ribosomal internal transcribed spacer regions 1 and 2, b-tubulin and translation elongation factor 1-a gene regions confirmed that the African group represents a distinct species within the hardwood lineage of the O. piceae complex, closely related to O. ulmi and O. himalulmi. Mating studies between O. quercus and the African isolates showed that isolates mated predominantly with those of their own group, although there were rare cases of fertile crosses between the groups. Isolates residing in the African lineage are described here as a new species, O. tsotsi sp. nov.

Eight polymorphic markers were developed from South African isolates of Ophiostoma quercus. The genome was screened for repeat regions using the fast isolation by amplified fragment length polymorphism of sequences containing repeats protocol and 20 de novo primer pairs flanking putative microsatellite regions were designed. Eight loci were optimized and their polymorphisms evaluated by sequencing. The repeat and flanking regions were highly polymorphic containing both indels and base-pair substitutions revealing a total of 46 alleles in 14 isolates and an average heterozygosity of 0.68. Substantial sequence variability makes these markers useful for genotyping populations in order to calculate diversity and monitor global movement of O. quercus.

Ophiostoma species such as O. quercus are the most frequent causal agents of sapstain of freshly felled hardwood timber and pulpwood. Many species are regarded as economically important agents of wood degradation. The aim of this study was to identify a collection of Ophiostoma isolates, resembling O. quercus, found on stained Eucalyptus pulpwood chips in China. DNA sequences of the internal transcribed spacer regions, including the 5.8S region, of the ribosomal DNA, and parts of the β-tubulin and elongation factor-1α genes, revealed that the isolates were not O. quercus. Surprisingly, they represented O. tsotsi, a wound-infesting fungus recently described from hardwoods in Africa. In addition, sequence data from an isolate from agarwood in Vietnam, identified in a previous study as belonging to an unknown Pesotum species, were also shown to represent O. tsotsi. A high level of genetic variability was observed among isolates of both O. quercus and O. tsotsi. This was unexpected and suggests that both species have been present in Asia for a significant amount of time.

Ophiostoma species such as O. quercus are the most frequent causal agents of sapstain of freshly felled hardwood timber and pulpwood. Many species are regarded as economically important agents of wood degradation. The aim of this study was to identify a collection of Ophiostoma isolates, resembling O. quercus, found on stained Eucalyptus pulpwood chips in China. DNA sequences of the internal transcribed spacer regions, including the 5.8S region, of the ribosomal DNA, and parts of the b-tubulin and elongation factor-1a genes, revealed that the isolates were not O. quercus. Surprisingly, they represented O. tsotsi, a wound-infesting fungus recently described from hardwoods in Africa. In addition, sequence data from an isolate from agarwood in Vietnam, identified in a previous study as belonging to an unknown Pesotum species, were also shown to represent O. tsotsi. A high level of genetic variability was observed among isolates of both O. quercus and O. tsotsi. This was unexpected and suggests that both species have been present in Asia for a significant amount of time.