Viegasella Inácio & P.F. Cannon, Mycol. Res. 107(1): 82 (2003).
Index Fungorum number: IF 28709; Facesoffungi number: FoF 02343, 1 morphological species (Species Fungorum 2022), no molecular data available.
Colonies superficial on the upper surface of leaves, rarely confluent. Sexual morph: Ascostromata black, circular or stellate, multilocular, opening by longitudinal splits, on pale to olive brown leaf spots marking the extent of the internal stroma. Exterior mycelium absent. Internal mycelium composed of irregularly branched hyaline hyphae connected to intracellular haustoria, with scattered dark brown columnar structures. Conidiomata absent. Ascomatal locules round, ellipsoidal or elongate. Interascal tissue composed of cellular pseudoparaphyses, pale brown and verrucose at the tips. Asci cylindric-clavate to clavate, thick-walled, not blueing in iodine, 6- to 8-spored, with rostrate dehiscence. Ascospores cylindric-ellipsoidal to ellipsoidal, pale brown, verrucose,uniseptate. Asexual morph: Unknown (adapted from Inácio and Cannon 2003).
Type species: Viegasella pulchella (Speg.) Inácio & P.F. Cannon
Notes: Viegasella is characterised by black, circular or stellate, multilocular ascostromata, ellipsoidal or elongate ascomatal locules, cylindric-clavate to clavate asci and cylindric-ellipsoidal to ellipsoidal verrucose,uniseptate ascospores. Inácio and Cannon (2003) treated Viegasella in Parmulariaceae based on morphology. Viegasella differs from Parmularia in having an internal stroma which extends below the cuticle outside the margins of the ascostroma, giving a pale olive-cream border appearance to the black fruiting bodies while Parmularia has a rather circular stroma with radiating locules. Viegasella also differs from Parmularia in having well-developed pseudoparenchymatous structures and presence of external hyphae while Viegasella has poorly developed hyphal internal stroma. Viegasella resembles Symphaeophyma in having an association with Sapotaceae but differs in that Symphaeophyma has an internal stroma visible from the leaf surface as purplish-black regions while Viegasella has olive cream coloration around the stromata. Viegasella also resembles Mintera in having black, gregarious, star-shaped ascostromata. Viegasella differs from Mintera in having brown superficial hypopodiate mycelium while Mintera has dark brown hyphae with appressoria, forming under the ascostromata. Viegasella is also similar to Aldonata in having ascomata with grayish-white to reddish lines surrounding the colony but differs in that Viegasella has small black spots nearby ascomata at the edge of leaf spots anduniseptate ascospores while Aldonata has tiny black conidiomata at center of leaf spots surrounded by the ascomata with muriform ascospores (Inácio and Cannon 2003). The asexual morph of Viegasella is unknown. The holotype specimen of Viegasella pulchella, collected in 1883 from Guarapi, Paraguay was deposited in LPS herbarium but is lost. Dai et al. (2020) re-examined a specimen from S herbarium, provided an illustration and treated Viegasella in Parmulariaceae. Viegasella is a distinct genus in Parmulariaceae but molecular data is needed to confirm this taxonomic placement.