About Botryosphaeria dothidea (Moug.) Ces. & De Not.
Botryosphaeria dothidea is the type species of the genus Botryosphaeria. Following a recent emendment to the International Code of Nomenclature for algae, fungi, and plants by the International Botanical Congress that requires a single name for one fungal species, the separate naming of the sexual (teleomorphic) and asexual (anamorphic) life stages of single fungal species is no longer standard practice. By current definition, B. dothidea was originally the name given to this species’ teleomorphic form, while Fusicoccum aesculi is the name that was given to its anamorphic form. In 2013, Phillips et al. chose to use the genus name Botryosphaeria rather than Fusicoccum, because Botryosphaeria is in common use and it is the type genus of the family Botryosphaeriaceae. Fries first published a description of this species as Sphaeria dothidea in Systema Mycologicum in 1823. Cesati and De Notaris later described the new genus Botryosphaeria, and moved the species formerly called S. dothidea into this new genus. When researchers confirmed no type specimen matching the original description of Sphaeria dothidea collected on ash existed, Slippers et al. (2004) designated an epitype specimen to accompany a non-sporulating neotype from Fries’ original collection, then published a revised description of B. dothidea. It is thought that the name B. dothidea previously covered a full species complex, so references to this name in older literature may refer to other species that have since been reclassified. Like other members of the class Dothideomycetes, the sexual stage of B. dothidea produces bitunicate asci. These asci develop inside hollow structures called ascomata, formed via a process called ascolocular development. For B. dothidea, these ascomata take the form of pseudothecia. The asci inside pseudothecia produce ascospores that can infect plants. Like other species in the order Botryosphaeriales, B. dothidea’s ascomata have multilayered dark brown walls and contain transparent (hyaline) septate pseudoparaphyses. B. dothidea’s pseudothecia may occur either singly or in clusters. In its asexual stage, B. dothidea produces infective conidia inside structures called pycnidia. The pycnidia and pseudothecia of B. dothidea are very similar in appearance. Microconidia, small asexual spores that often act as male gametes or gametangia (spermatia) during cytoplasmic fusion (plasmogamy), have been recorded in at least one isolate of B. dothidea. According to an identification key from Phillips et al. (2013), B. dothidea can be distinguished from six other species in the Botryosphaeria genus by its conidia: these conidia are typically longer than 20 μm, have a length-to-width ratio greater than 4.5, and are found on hosts that are not Vaccinium species. The conidia are narrowly or irregularly fusiform, have thin walls, and are generally transparent (hyaline) and aseptate. Older conidia may sometimes develop up to two septa and/or darken in color. Morphological differentiation between related Botryosphaeria species requires observing multiple samples to identify the most common character states, and collecting samples at the correct developmental stage. DNA sequencing is considered an important complementary tool to morphological identification of this species.
