Rhabdocline Syd., in Sydow & Petrak, Annls mycol. 20(3/4): 194 (1922)
= Meria Vuill., C. r. hebd. Séanc. Acad. Sci., Paris 122: 546 (1896)
= Rhabdogloeum Syd., in Sydow & Petrak, Annls mycol. 20(3/4): 215 (1922)
Facesoffungi number: FoF 07572
Leotiomycetes, Leotiomycetidae, Helotiales, Hemiphacidiaceae
Saprobic or parasitic on the host plant in terrestrial habitat. Sexual morph: see Parker and Reid (1969). Asexual morph: two types a) sporodochial asexual morph (e.g. Meria), see Sherwood-Pike et al. (1986) and Gernand et al. (1997); b）acervular asexual morph (e.g. Rhabdogloeum). Conidiomata pale ochraceous to orange-yellow, gelatinous amphigenous, acervular, solitary to gregarious or confluent, rounded to oval, unilocular, glabrous, thick-walled, dehiscing by a split in the host epidermis. Ostiole absent. Conidiomatal wall composed of hyaline, thin-walled cells of textura angularis at base. Conidiophores arising from the upper cells of the basal stroma, hyaline, branched, septate. Conidiogenous cells hyaline, cylindrical to ampulliform, discrete or sometimes integrated, smooth-walled, proliferating one or two times. Conidia hyaline, cylindrical to ellipsoid, straight or slightly curved, narrowed at middle zone, aseptate, smooth-walled, guttulate, bearing a filiform, curved, apical, mucoid appendage.
Type species: Rhabdocline pseudotsugae Syd., Annls mycol. 20(3/4): 194 (1922)
Notes: Rhabdogloeum was introduced by Sydow and Petrak (1922) to accommodate a single species R. pseudotsugae, collected on living leaves of Pseudotsuga taxifolia in North America, together with a new genus Rhabdocline described from same host. Therefore, Sydow (1922) suggested Rhabdocline to be the sexual morph of Rhabdogloeum. Two additional species, R. abietinum Dearn. collected on leaves of Abies fraseri and R. hypophyllum D.E. Ellis & L.S. Gill collected on leaves of P. taxifolia were included in Rhabdogloeum (Dearness 1928, Ellis and Gill 1945). However, Rhabdogloeum abietinum was later considered a synonym of Rhabdogloeopsis balsameae, and R. hypophyllum was transferred to Cryptocline Petrak (Nag Raj and Morgan-Jones 1973).
Parker and Reid (1969) reported that Rhabdocline weirii A.K. Parker & J. Reid was associated with Rhabdogloeum pseudotsugae based on culture study. Therefore, Rhabdogloeum was reduced to a synonym of Rhabdocline (Johnston et al. 2014, Wijayawardene et al. 2017). Except for Rhabdogloeum asexual morph, Rhabdocline species have also been reported to have a Meria asexual morph based on ITS sequence data (Sherwood-Pike et al. 1986, Gernand et al. 1997, Stone and Gernandt 2005). Meria is a hyphomycetous taxon which has sporodochial conidiomata, and oblong conidia without appendages, while Rhabdogloeum is a coelomycetous taxon with acervular conidiomata producing cylindrical to ellipsoid conidia with apical appendages (Sherwood-Pike et al. 1986, this study). The asexual morph of R. weirii (= Rhabdogloeum pseudotsugae) has not been studied by molecular data, thus further investigations based on fresh collections and phylogenetic inferences with multi-loci sequence are needed. We re-examined herbarium specimen of asexual Rhabdocline weirii and provide a detailed description and plate for further reference.
Distribution: Canada, USA (Parker and Reid 1969, Sherwood-Pike et al. 1986, this study)
Li WJ, McKenZie EHC, Liu JK, Bhat DJ, Dai DQ, Caporesi E, Tian Q, Maharachcikumbura SSN, Luo ZL, Shang QJ, Zhang JF, Tangthirasunun N, Karunarathna SC, Xu JC, Hyde KD (2020) Taxonomy and phylogeny of hyaline-spored coelomycetes. Fungal Diversity 100: pages279–801.