Appearance
''Botryosphaeria dothidea'' is the type species of the genus ''Botryosphaeria''. While the International Botanical Congress recently emended the International Code of Nomenclature for algae, fungi, and plants to state that one fungal species should be called by one name, the sexual and asexual stages of single fungal species have often been called by different names. ''B. dothidea'' was the name given to the teleomorphic form, and ''Fusicoccum aesculi'' has been identified the anamorph of ''B. dothidea'', as currently defined. Phillips et al. chose to use the genus name ''Botryosphaeria'', rather than ''Fusicoccum'', since ''Botryosphaeria'' is commonly used and is the type genus of the family Botryosphaeriaceae.Fries first published a description of ''B. dothidea'' as ''Sphaeria dothidea'' in ''Systema Mycologicum'' in 1823. Cesati and De Notaris described the genus ''Botryosphaeria'' and moved the species formerly known as ''S. dothidea'' into the new genus.
After determining that a type specimen consistent with the original description of ''Sphaeria dothidea'', on ash, did not exist, Slippers et al. designated an epitype specimen to go along with a non-sporulating neotype from the collection of Fries, who published the original description of the species. Slippers et al. then revised the description of ''B. dothidea''. The name is believed to have previously encompassed a species complex, and references to it in older literature might represent species now otherwise identified.
Like other members of the Dothideomycetes, the sexual stage of ''B. dothidea'' has bitunicate asci, which are borne in cavities formed through a process known as "ascolocular development". In the case of ''B. dothidea'', these ascomata are pseudothecia. The asci in the pseudothecia produce ascospores that can then infect plants. Like other species in the order Botryosphaeriales, ''B. dothidea'' ascomata have "multilayered dark brown walls" and contain septate pseudoparaphyses which are transparent or translucent . Pseudothecia are sometimes located alone and other times clustered together.
In the asexual stage, conidia, which can also infect plants, are produced in pycnidia. The pycnidia and pseudothecia of ''B. dothidea'' look very similar. Microconidia have also been reported in at least one ''B. dothidea'' isolate. Microconidia are small, asexual spores that often act as male gametes or gametangia in a process of cytoplasmic fusion
According to a key provided in Phillips et al. , ''B. dothidea'' can be distinguished from six other members of the genus by conidia that are typically longer than 20 μm, have a length to width ratio greater than 4.5, and occur on hosts other than ''Vaccinium'' species. These conidia are "narrowly...or irregularly fusiform," have thin walls, and are generally transparent or translucent and aseptate but sometimes form up to two septa and/or darken when they are older. Differentiating between species based on morphology depends on observing multiple samples, to get an idea of prevailing character states, and doing so at the appropriate developmental stage. Sequencing is considered an important companion to morphological identification
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