Marantokordyana oberwinkleriana
Marantokordyana oberwinkleriana M. Piepenbr., Maike Hartmann, T.A. Hofm. & M. Lutz in M. Piepenbr et al., Mycological Progress 19 (4): 357 (2020)
Etymology: This species is named in honor of Franz Oberwinkler (1939–2018) who made important contributions to the knowledge of heterobasidiomycetes (comp. Piepenbring et al. 2019).
Diagnosis: Leaf blades with scattered to numerous spots due to infection. Infected areas elongated rectangular and rounded at the ends, laterally delimited by veins of the leaf blade, not swollen, in surface view mostly (3–)4–10(−11) × (1.5–)2– 2.5(−3) mm (n = 10), sometimes larger by fusion, adaxially yellow to slightly orange colored, abaxially white surrounded by a ring of tissue of yellowish color, with white balls of basidia evident with a hand lens or a stereomicroscope. All the substomatal chambers of an infected area filled by fungal hyphae in dense stromata, hyphae protruding through the stomatal openings, developing balls of basidia mixed with paraphyses, one ball on the top of each stoma, balls of basidia easily breaking off and being dispersed.
Substomatal chambers filled with fungal stroma formed by dense fungal hyphae, more voluminous than substomatal chambers without fungal stroma (Fig. 4), cellular details of fungal stroma difficult to distinguish, in very thin sections three types of fungal hyphae distinguishable, very thin hyphae at the base of the stroma approx. 1 µm diam., thin hyphae approx. 1.5 µm diam. mixed with the thick hyphae, thick hyphae approx. 3 µm diam. with swelling of up to 5 µm diam. at the base.
Balls of basidia spherical to globose, composed of basidia of different ages and paraphyses of 1.5 µm diam. densely packed in the centre and loosely exposed at the surface of a ball, (40-)55-80(-90) µm diam. (n=20), white.
Basidia holobasidia, with basidial cell cylindrical, of variable length of up to at least 70 µm, sometimes shorter by retraction septa formed during sporulation, basidia 3-4(4.5) µm diam. (n=10), thinner after the liberation of the basidiospores, with two apical, straight or bent, elongated and often slightly swollen sterigmata of 1.5-2 x (2-)3.5-6.5(-7.5) µm (n=20), with one basidiospore developing at the tip of each sterigma. After liberation of the basidiospores basidial cells empty, sometimes with scattered tiny rests of plasma, with scars evident at the tips of the sterigmata.
Basidiospores liberated single or in pairs, at the moment of liberation one-celled but soon afterwards two-celled due to a central septum, cylindrical or slightly allantoid and slightly fusoid at the base, with a conspicuous hilum (scar) at the base of each basidiospore, 3-4.5(-6) x (10-)11-16(-19) µm (n=30), hyaline, smooth, densely filled with oil drops or with homogenous plasm. The two basidiospores of one basidium conjugating by fusing at their bases or individual basidiospores germinating with hyphae of about 1 µm diam. originating at their tips or laterally and developing conidia on more or less evident sterigma-like outgrowths or cells of basidiospores directly developing conidia usually at their tips.
Conidia mostly one-celled, rarely with septum, rod-shaped to fusiform or slightly allantoid, with scar at the point of detachment, (0.5-)1(-1.5) x 3-8(-11) µm (n=20), hyaline, smooth, germinating with thin hyphae or budding forming further conidia (yeast cells).
Index Fungorum Number: IF 832384
Reference:
Piepenbring, M., Hartmann, M., Hofmann, T. A., & Lutz, M. 2020. Two new species in a new genus and a critical revision of Brachybasidiaceae (Exobasidiales, Basidiomycota) in honor of Franz Oberwinkler. Mycological Progress, 19(4), 351-365.
Figure 1. Species of Marantokordyana. a–c M. oberwinkleriana on Goeppertia panamensis (MP 5127). a Infected plant in the field. b The upper side and the lower side of leaf blades with leaf spots. c A leaf spot seen from the lower side of the blade by a stereomicroscope. Each white dot is a ball of basidia. Scale bar = 2 mm. d–f M. boliviana on Goeppertia propinqua (CH 11). d Infected plant in the field. e The upper side of a leaf blade with leaf spots. f Leaf spots seen from the lower side of the blade. White dots are balls of basidia
Figure 2. Marantokordyana oberwinkleriana on Goeppertia panamensis (MP 5412, holotype). a Transverse section of a leaf showing abaxial mesophyll, the abaxial epidermis, substomatal chamber filled with fungal cells (stroma), and a ball of paraphyses and basidia that liberated basidiospores single or in pairs. B Transverse section of a leaf showing abaxial mesophyll, the abaxial epidermis, and a substomatal chamber without fungal cells. Scale bars = 10 μm
Figure 3. Marantokordyana oberwinkleriana (M 409, MP 5127). a Tips of young and sporulating basidia. b Tip of a paraphysis of a ball of basidia. c Basidiospores single or in pairs. d Two basidiospores connected by a conjugation bridge at their bases. e Tips of basidia after liberation of basidiospores. f Germinating basidiospores. g Conidia budding as yeasts. Scale bars = 10 μm
Figure 4. Marantokordyana boliviana (CH 88). a Fungal cells isolated from a substomatal chamber, without adjacent host cells. Thick hyphae with probasidial swellings directed towards the stomatal opening (not shown) and thin, indistinguishable hyphae filling the space in between. b Basidia after the liberation of basidiospores. c Liberated basidiospores in pairs, one pair with a conjugation bridge at the base. d Conjugated basidiospores germinating with hyphae. Note the retraction septum in the cell on the left hand side. e One half of a basidiospore forming a conidium at the tip of a hypha. Note the retraction septum. f Yeast-like conidia budding or forming conidia on sterigma-like outgrowths. g An intercalary cell of a hypha with an outgrowth developing a conidium. h A hypha developing conidia. Septa of the hypha are difficult to distinguish. Scale bars = 10 μm
Reference:
Piepenbring, M., Hartmann, M., Hofmann, T. A., & Lutz, M. 2020. Two new species in a new genus and a critical revision of Brachybasidiaceae (Exobasidiales, Basidiomycota) in honor of Franz Oberwinkler. Mycological Progress, 19(4), 351-365.
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