Geastrumia
Geastrumia Bat., in Batista, Farr & Bezerra, Saccardoa 1: 71 (1960)
Dothideomycetes, Dothideomycetidae, Capnodiales, Mycosphaerellaceae
Saprobic or parasitic on the host plant. Mycelium superficial, composed of brown to pale brown, branched, septate hyphae (Pirozynski 1971, Sutton 1980). Sexual morph: undetermined. Asexual morph: Conidiomata dark brown to black, pycnidial, discrete or irregularly scattered, superficial, sessile, at first closed and globose, later opening widely and become cupulate, unilocular, glabrous. Ostiole absent, dehiscence by irregular splits of the apical wall. Conidiomatal wall composed of thin-walled, pale brown cells of textura angularis in the basal part, becoming one cell thick, dark brown cells of textura globulosa at the lateral and upper part. Conidiophores formed from the repent hyphae at the base and at the point of their transformation into the covering wall, hyaline, branched and septate at the base, tapered towards the apex, smooth-walled. Conidiogenous cells hyaline, holoblastic, narrowly ampulliform to cylindrical, integrated or discrete, determinate, smooth-walled. Conidia hyaline, staurosporous, composite, consisting of 6–14 arms, fusiform, straight or slightly curved, up to 15-eptate invested in mucus, and remaining attached to a common branched, long-pedicellate basal cell even after liberation (Nag Raj and DiCosmo 1978).
Type species: Geastrumia polystigmatis Bat. & M.L. Farr, in Batista, Farr & Bezerra, Saccardoa 1: 71 (1960)
Notes: Geastrumia polystigmatis was collected from living leaves of Andira jamaicensis (Fabaceae) in the Dominican Republic (Pirozynski 1971). The genus is characterized by pycnidial, superficial conidiomata, holoblastic conidiogenous cells and staurosporous conidia with 4–16 arms, fusiform arms. Santos (2011) described two unnamed taxa Geastrumia sp. 1 and Geastrumia sp. 2 from leaves of Salacia crassifolia (Celastraceae) in Brazil. Geastrumia sp. 2 differs from G. polystigmatis and Geastrumia sp. 1 by its larger conidiomata and brown conidia. Geastrumia sp. 1 has shorter conidial arms than the other taxa. Ismail et al. (2016) included molecular data for G. polystigmatis and showed that is related to Mycosphaerellaceae. Fresh collections of the unnamed taxa are needed to confirm generic placement.
Distribution: Brazil, Dominican Republic, Thailand (Pirozynski 1971, Santos 2011).
Geastrumia polystigmatis (redrawn from Pirozynski 1971, Nag Raj and DiCosmo 1978) a Slide view of conidiomata. b Conidiogenous cells and conidia.
References:
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.
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