Periglandula, a new fungal genus within the Clavicipitaceae and its association with Convolvulaceae

We describe two newly discovered fungi living on the adaxial leaf surface of plants belonging to the Convolvulaceae, Ipomoea asarifolia and Turbina corymbosa. The fungi apparently are epibionts because hyphae were never observed to penetrate epidermal cells or stomata of their respective host plants, and most remarkably are intimately associated with secretory glands on the leaf surface. Hyphae and structures resembling chlamydospores and synnemata (but lacking conidia), formed by both fungal species are phenotypically nearly indistinguishable after in vitro growth or when examined in vivo on the leaf surface. Phylogenetic trees based on aligned DNA sequences from nuclear genes for β-tubulin (tubB) and RNA Polymerase II subunit 1 (rpbA), and the mitochondrial gene for ATP synthase F0 subunit A (atp6), grouped the fungal species in a clade within the Clavicipitaceae. Clavicipitaceous fungi isolated from the two different plant species could be distinguished by their atp6 and rpbA sequences, and nuclear genes for γ-actin (actG), translation elongation factor 1-α (tefA), and 4-(γ,γ-dimethylallyl)tryptophan synthase (dmaW), the determinant step in ergoline (i.e. ergot) alkaloid biosynthesis. Based on these findings we propose a new fungal genus, Periglandula, gen. nov., and describe two new species, Periglandula ipomoeae sp. nov., from host plant I. asarifolia, and Periglandula turbinae sp. nov., from T. corymbosa.