Morpho-molecular characterization of phoma-like fungi from Morus alba in northern Thailand; a novel species (Boeremia albae) and a new host record (B. maritima)

Abstract

Boeremia was established to accommodate phoma-resembling fungi. Its species occur in terrestrial ecosystems as endophytes, saprobes and pathogens, except one species reported from a marine ecosystem. Boeremia species are characterized by hyaline, thin-walled, and aseptate (occasionally 1(–2)-septate) conidia that are variable in shape, and hyaline, straight or slightly curved, thick-walled, and 1-septate ascospores that are usually constricted at the septum. In the past, host associations were used to delimit Boeremia species. However, since Boeremia taxa have overlapping morphological characters and are cryptic, it renders taxonomic identification arduous. Therefore, the use of other approaches including multi-gene phylogenetic analyses are imperative. Recommended DNA markers for species delineation are the internal transcribed spacer (ITS, nuclear rDNA consisting of ITS1-5.8S-ITS2) and large subunit (28S, D1–D2 domains of nuclear 28S rDNA) loci, and the genes for actin (ACT1), beta-tubulin (TBB1), RNA polymerase 2 (RPB2) and translation elongation factor 1α (TEF1). Here, we applied morphological and molecular phylogenetic analyses to establish a new taxon (B. albae), and a new host and geographical record for B. maritima associated with leaf spots of Morus alba (Moraceae) in northern Thailand. By providing sequence data for three additional gene regions, our phylogenetic analyses impart a stable phylogenetic placement of the ex-type strain of B. maritima, as illustrated. This is the first study that reports Boeremia species from M. alba, and B. maritima from a terrestrial habitat.