Diaporthe salsuginosa Vrijmoed, K.D. Hyde & E.B.G. Jones, Mycol. Res. 98: 699 (1994)
Index Fungorum number: IF 362640
Saprobic on decaying wood of Avicennia marina. Sexual morph: Ascomata solitary or clustered, enclosed within a wide spreading blackened zone in the wood, both above the ascomata (dorsal zone) and below (ventral zone). Stromata appears as fine black lines when the substrate is cut at right angles to the surface; ascomata up to 160–300 µm high, 200–285 µm diameter (x̅ = 224 × 248 µm, n = 10), brown or black, immersed, coriaceous, commonly in small groups, in crater-like, darkened depressions (discs) on the wood surface. Blackened stromatic development around the area of clustered ascomata, which is variable and is composed of host cells filled with irregular brown fungal hyphae, with short ostioles piercing the host surface singly. Ostiole 40–100 µm high, 25–60 µm diameter (x̅ = 68 × 50 µm, n = 5), mostly immersed with short portion projecting above host surface, brown with periphyses. Peridium 20–40 µm (x̅ = 25 µm, n = 20), wide, composed of pallid elongate cells inwardly and brown thin-walled cells of textura angularis at the outside. The basal cells are hyaline. Paraphyses hypha-like, 2–4 µm wide at the base, filiform, tapering distally, septate. Asci 37–70 × 4–10 µm (x̅ = 52 × 7 µm, n = 20), 8-spored, unitunicate, thin-walled, cylindrical, short pedicellate, apically flattened with an iodine negative subapical ring, developing in the hymenium at the base of the ascomata. Ascospores 8–15 × 2.5–5 µm (x̅ = 10 × 3 µm, n = 30), hyaline, guttulate, 1–2-seriate, fusoid, 2-celled, smooth-walled, with or without constriction at the septum, with a small mucilaginous pad at each end which swells in water and attaches the spore to the glass slide. Asexual morph: Conidiomata 420–630 × 275–470 µm (x̅ = 470 × 376 µm, n = 5) in diam., pycnidial, superficial, aggregated in groups on MEA, stromatic, ostiolate, multilocular, globose, dark brown to black. Peridium 50–110 µm (x̅ = 74 µm, n = 5), thick, composed of thick-walled cells of textura angularis. Conidiophores 25–40 × 1–2 µm (x̅ = 31 × 1.5 µm, n = 10), branched, filiform, aseptate, densely aggregated. Conidiogenous cells subcylindrical, straight to curved, hyaline, tapering towards the apex. Alpha conidia 6–9 × 1.5–2.5 µm (x̅ = 7.5 × 2 µm, n = 5), hyaline fusiform or oval with obtuse ends rarely found. Beta conidia 25–40 × 1.5–2 µm (x̅ = 27 × 1.2 µm, n = 10), filiform, hamate, eguttulate, aseptate tapering towards both ends.
Culture characteristics – Ascospores germinating on 50% sea water agar within 24 hours, with germ tubes developed from both ends of the cell and lateral sides of ascospores. Colonies on MEA, reaching 45–55 mm diam., after 7 days of incubation at 25°C, flat with an entire edge, surface hyaline to creamy initially, reaching pale yellow to dark brown at maturity, reverse hyaline to pale yellow, filamentous, cottony texture, circular, raised.
Material examined – India, Tamil Nadu, Parangipettai mangroves (11.59°N 79.5°E), on decaying wood of Avicennia marina (Acanthaceae), 23 April 2018, B. Devadatha AMH-10013, living culture (NFCCI-4385).
GenBank numbers – ITS: MN061372, LSU: MN061362, SSU: MN173346, RPB2: MN546859, TEF1-α: MN184789.
Known distribution (based on molecular data) – India, Tamil Nadu, Parangipettai (Vrijmoed et al. 1994, Jones et al. 2015)
Known hosts (based on molecular data) – Avicennia marina, Kandelia candel (Vrijmoed et al. 1994, Jones et al. 2015)
Notes – Diaporthe salsuginosa was described from decaying mangrove wood by Vrijmoed et al. (1994) based on morphological characteristics. We provide multi-gene sequence data for this species. Diaporthe salsuginosa is distinct from other Diaporthe species in having unique 1-septate ascospores with bipolar mucilaginous pads which swell in water. Our collection of D. salsuginosa (AMH-10013) is similar to the protologue of D. salsuginosa, but distinct in having constrictions at the septum and they have an asexual stage. In the phylogenetic analysis of combined ITS and β-TUB genes, D. salsuginosa clusters with D. eucalyptorum with significant support (ML 96%, 0.9 BYPP). Diaporthe salsuginosa can be distinguished from D. eucalyptorum (sexual morph) in having smaller stromatic ascomata, longer ascospores with guttules and a small mucilaginous pad at each end, and an asexual stage with larger pycnidia and containing both alpha and beta conidia. Diaporthe eucalyptorum was reported as an asexual morph from leaves of Eucalyptus (Crous et al. 2012). In the present study, we connect D. salsuginosa to the sexual morph. Diaporthe salsuginosa is the only species reported from the marine environment (Jones et al. 2015).
Fig – Diaporthe salsuginosa (AMH-10013, a new asexual-sexual linkage). a Section of ascomata. b Peridium. c–g Immature and mature asci. h–j Ascospores with polar appendages. k Germinating ascospore. l Pycnidia developed on culture. m Conidia. Scale bars: a = 100 μm, b–k = 10 μm, l = 200 μm.