Rhizotexis
Rhizotexis Theiss. & Syd., Annls mycol. 15(1/2): 140 (1917).
Index Fungorum number: IF 4715; Facesoffungi number: FoF 12451, 1 morphological species (Species Fungorum 2022), no molecular data available.
Epiphytic on lower surface of living leaves. Sexual morph: Ascostromata solitary to gregarious, irregular, black, coriaceous, stromatic. Ascostromata wall composed of brown to dark brown cells of textura angularis, with side wall. Locules superficial, globose to subglobose to irregular, black, non-ostiolate, containing a few asci. Hamathecium with asci and remnants of thin-walled, pseudoparenchymatous cells; pseudo paraphyses not seen. Asci 8-spored, bitunicate, broadly cylindrical, ellipsoidal to clavate, pedicellate, apically rounded and thickened, with an ocular chamber. Ascospores 2–4-seriate, brown to dark brown, oblong,1-septate, septum supra median, upper cell broad and shorter, lower cell longer and oblong, ends rounded to slightly narrow, smooth-walled, constricted at the septum. Asexual morph: Unknown (adapted from Dai et al. 2014).
Type species: Rhizotexis bauhiniarum (Henn.) Theiss. & Syd.
Notes: Rhizotexis is characterised by solitary to gregarious, irregular, black, coriaceous ascostromata, globose to subglobose to irregular, black locules, broadly cylindrical, ellipsoidal to clavate, pedicellate asci and brown to dark brown, oblong,1-septate ascospores. Lumbsch and Huhndorf (2010), and Kirk et al. (2013) listed Rhizotexis in Englerulaceae. Dai et al. (2014) examined the syntype of R. bauhiniarum (B! 700014085) and excluded it from Englerulaceae based on its ascostromata with mostly single locules, lacking superficial hyphae or hyphopodia. Rhizotexis resembles members of Parmulariaceae for example, Parmularia, Parmulariopsis, Rhipidocarpon based on its locules developing in black ascostromata. Rhizotexis differs from other genera in Parmulariaceae in having small, irregular, protuberant ascostromata lacking ostioles and hamathecium lacking hyphal filaments while members of Pamulariaceae have large, globose to subglobose, flattened pseudothecia with long ostioles and hamathecium with hyaline to dark brown filaments (Inácio 2008, Dai et al. 2014). Rhizotexis bauhiniarum resembles Asterotexis cucurbitacearum in having black stromatic ascomata growing on leaf surfaces and similar stromatic wall but differs in that the former has smaller ascomata and is reported from Bauhinia longipetala while Asterotexis cucurbitacearum has larger ascomata (over 1 mm) and is reported from Cucurbita pepo and Sechium edule (Cucurbitaceae) (Theissen & Sydow 1914, Arx & Müller 1975, Guerrero 2011, Dai et al. 2014). Dai et al. (2014) suggested that Rhizotexis and Asterotexis are closely related to each other but molecular data is lacking to prove this. Dai et al. (2014) and Wijayawardene et al. (2017, 2020) referred Rhizotexis in Dothideomycetes genera incertae sedis. Fresh collections with DNA sequence data are needed to confirm the systematic position of Rhizotexis.
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