Polyrhizon
Polyrhizon Theiss., Syd. & P. Syd., Annls mycol. 12(3): 281 (1914).
Index Fungorum number: IF 4319; Facesoffungi number: FoF 12423, 7 morphological species (Species Fungorum 2022), no molecular data available.
Saprobic on leaves of dicotyledons. Sexual morph: Ascostromata producing round, black spots in leaves. Ascomata gregarious in the ascostromata, immersed to erumpent, globose, subglobose, or broadly conical. Peridium 1-layered, composed of small, lightly pigmented, thick-walled cells of textura prismatica. Hamathecium of dense, long cellular pseudoparaphyses, anastomosing and branching between and above the asci. Asci 8-spored, bitunicate, fissitunicate, cylindrical to fusoid, with a short furcate pedicel, which is less than 10 μm long, with a small ocular chamber. Ascospores biseriate, broadly fusoid to subclavate with broadly to narrowly rounded ends, reddish brown, uniseptate, constricted at the septum, the upper cell often broader and shorter than the lower one, baculate. Asexual morph: Unknown (adapted from Zhang et al. 2011).
Type species: Polyrhizon terminaliae (Syd. & P. Syd.) Syd. & P. Syd.
Notes: Polyrhizon is characterised by globose, subglobose, or broadly conical ascomata, bitunicate, fissitunicate, cylindrical to fusoid asci and biseriate, broadly fusoid to subclavate ascospores. Lumbsch and Huhndorf (2010) and Kirk et al. (2013) accepted Polyrhizon in Venturiaceae. Zhang et al. (2011) examined the holotype specimen of P. terminaliae (S reg. nr F8238, as Dothidea terminaliae) and excluded Polyrhizon from Venturiaceae based on the persistent cellular pseudoparaphyses, broadly clavate asci with short furcate pedicels, and the almost median septate, baculate ascospores which is atypical of members of Venturiaceae. Zhang et al. (2011) suggested that Polyrhizon might belong to Pleosporineae (Pleosporales) but molecular data is lacking to confirm this statement. Wijayawardene et al. (2017, 2020) referred Polyrhizon to Dothideomycetes genera incertae sedis. Fresh collections with DNA sequence data are needed to confirm the systematic position of Polyrhizon.
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