Abradeosporangium, a new genus of Mucorales (Fungi: Zygomycetes) from India
A. Subrahmanyam 1, A. Swathi Sri 2 & Vatsavaya S. Raju 3
1,2 Department of Biotechnology, Meerut Institute of Engineering and Technology, NH 58, Baghpat Bypass Cross, Meerut,
Uttar Pradesh, 250005, India
3 Plant Systematics Laboratory, Department of Botany, Kakatiya University, Warangal, Andhra Pradesh 506009, India
Email: 1 email@example.com; 3 firstname.lastname@example.org (corresponding author)
During the course of exploration of fungi of Meerut district, Uttar Pradesh, India, an interesting isolate bearing dimorphic sporangia on distinct sporangiophores was discovered from the rat excreta and decomposing Hibiscus flowers gathered from the campus of Meerut Institute of Engineering and Technology (MIET). Some of the macrosporangia dehisce along a longitudinal suture as in Blakeslea and Gilbertella (Binny 1991). However, the present isolate differs from both these genera in several diagnostic characters. Hence, it is warranted to accommodate the present isolate in a new genus of Mucorales.
Abradeosporangium Subrahm. et A. Swathi Sri, gen. nov.
(Mucorales, Zygomycetes) (Image 1; Figs. 1-5)
Material examined: Holotype: 08.x.2008, Anamorph, soil and decomposing Hibiscus flowers, MIET Campus, Meerut, India, coll. A. Swathi Sri (MIET Culture Bank: Fungi 126) (MycoBank # 518785).
Sporangia dimorpha; macrosporangia globosa, atrobrunnea, columella nulla, multispora, parietus tenues, ad apicem et basim dissolutus ad maturitatus et sporae liberatus, aliquot sporangia dehisce longitudinalis. Microsporangia plus minus globosa, dilutus brunnea, multisporata, parietus glabrus, persistens et sutura longitudinalis nulla. Sporangiosporae globosae, variabilis, dilute brunneae vel brunneae, striatus longitudinalis minutus, plerumque ovalis, sporae globosae, raro fucus et dumbelliformes. Zygosporae nullae.
Sporangia dimorphic; macrosporangia globose, dark brown, acolumellate, multispored with smooth, thin-walled (peridium) which at maturity dissolves at the top and bottom to release the spores. Some of the sporangia split open along the longitudinal suture as in Blakeslea (Ho & Chang 2003) and Gilbertella (Hesseltine 1960; Mehrotra & Mehrotra 1963). Microsporangia nearly globose, pale brown, with variable number of sporangiospores; peridium smooth, persistent and without any longitudinal suture. Sporangiospores variable in shape, pale brown to brown, finely longitudinally striated, usually oval or globose, occasionally fusiform to dumbbell shaped. Zygospores absent.
Etymology: The generic name refers to breakage or dissolution of sporangium; L: abrādō: damage; sporangium.
Type species: Abradeosporangium variosporum, sp. nov.
Subrahm. et A. Swathi Sri, sp. nov.
(Image 1; Figs. 1-5)
Mycelium aseptatus, hyalinus, glabrus, ramosus; sporangiophorae hyalinae, lateralis, non-ramosus, aseptatae, statim inferne sporangiorum curvatae, producentes sporangia ad terminalis; sporangia dimorpha, producentes sporangiophores separatis. Macrosporangia magna, spherica, atrobrunnea, acolumellata, multispora, 101-109 µm diam.; parietus sporangiorum hyalinus, glabrus, persistentes; parietus inferne et ad apicem dissolutus et sporangiosporae liberatae; saepe sporangia dehiscentes longitudinalis. Microsporangia numerosa, producentes pedicellae lateraliter, dilute brunneae, sutura longitudinalis nulla, 12-42 µm diam.; sporangiosporae dilute brunneae vel brunneae, appendices nullae, striatus longitudinalis minutae, plerumque ovoideae, 7-10 x 3-5 µm, sporae globosae, ad 10µm diam., saepe dumbelliformes vel fusiformes; chlamydosporae intercalares vel termilnalis, glabrae, cylindraceae, solitariae, dilute brunneae, 6-8 x 1-2 µm; zygosporae nullae.
Mycelium aseptate, hyaline, smooth, branched; sporangiophores hyaline, lateral, unbranched, aseptate and curved proximate to the sporangium even at maturity, bear a single sporangium distally; sporangia dimorphic, born on separate sporangiophores. Macrosporangia large, spherical, dark brown, acolumellate, multispored, 101-109 µm in diam.; peridium smooth, persistent; but at maturity, part of the wall at the top and bottom gets dissolved to release the sporangiospores; a few sporangia split open along the longitudinal suture as in Blakeslea and Gilbertella (Table 1). Microsporangia numerous, born on small lateral stalks, pale brown with variable number of spores without longitudinal suture, 12-42 µm in diam.; sporangiospores lack appendages, pale brown to brown, smooth, finely longitudinally striated, shape variable, most commonly ovoid, 7-10 x 3-5 µm or globose, up to 10 µm in diam., occasionally dumbbell or fusiform shaped spores also formed; chlamydospores intercalary or terminal; smooth, barrel-shaped, single, pale brown, 6-8 x 1-2 µm; zygospores absent.
Culture characterization: The fungus grows on most of the common media like potato dextrose agar, 2% malt extract agar, oatmeal agar, YpSs agar and also on synthetic mucor agar.
(i) On oatmeal agar: Growth profuse; colonies at room temperature white to pale yellow, fast growing, cover 80mm plate in 72h. Aerial mycelium well-developed, appear granular with the development of sporangia; sporangia pale brown, turn black on maturation. Sporulation characteristically begins from periphery of the colony; reverse colony colourless; diffusible pigment absent.
(ii) On potato dextrose agar: Growth profuse; colonies at room temperature fast growing, cover 80mm plate in 72h. Mycelium dull-white, raised, zonate, crest and trough-like with depressed area at the centre. Sporulation characteristically begins from periphery of the colony in the aerial mycelium. It appears granular with the initiation of pale brown sporangia which turn black on maturation; reverse colony pale woody yellow; sporulation abundant.
On almost all media, the mycelial growth is zonate, crest-like and trough type; sporulation always begins from the periphery of the colony.
Abradeosporangium gen. nov. is a saprophytic mucoralian genus producing acolumellate dimorphic sporangia. On most of the mycological media, it produces crest and trough type growth. Sporulation characteristically begins from the periphery of the colony. It produces multispored, psilate macrosporangia. The sporangiophores are goose-necked even at maturity (dehiscence time). The release of sporangiospores is either through a longitudinal suture as in Gilbertella and Blakeslea, or by dissolving a part of the sporangial wall (peridium) at the top and bottom. The latter trait makes Abradeosporangium gen. nov. distinct. While Gilbertella and Blakeslea produce columellate sporangia (Table 1), the sporangia are acolumellate in the present isolate (Image 1; Fig. 1).
Furthermore, the microsporangia, unlike Blakeslea (Kirk 1984), are produced distally on simple sporangiophores and not on barrel-shaped pedicles covering the surface of globose vesicles. The suture present in the microsporangial wall of Blakeslea is wanted in Abradeosprongium gen. nov. Moreover, the sporangiospores are simple, longitudinally striated, ovoid or globose and do not bear hyaline appendages at the poles as in Blakeslea and Gilbertella. Besides, zygospores and rhizoids are wanted. Another interesting feature of the present isolate is that it fails to sporulate on slants.
Other distinct features of the new genus: Growth on most of the media is characteristically crest and trough type; sporulation always begins from the periphery of the colony. It sporulates freely in a plate but not in a tube. Several combinations like PDA + 2 % cow dung extract; soil extract + SMA agar; soil extract + cow dung extract, PDA + SMA - all of them incubated at 180, 240, 280 and 370 C but sporulation could not be induced in tube culture.
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