Alternaria omanensis Al Ghafri, Maharachch., Hyde KD & Al-Sadi, 2019

Ghafri, Abir Al, Maharachchikumbura, Sajeewa S. N., Hyde, Kevin D., Al-Saady, Nadiya A. & Al-Sadi, Abdullah M., 2019, A new section and a new species of Alternaria encountered from Oman, Phytotaxa 405 (6), pp. 279-289 : 285-286

Alternaria omanensis Al Ghafri, Maharachch., Hyde KD & Al-Sadi , sp. nov.

MycoBank: MB 830793 ( FIGS. 2 –4)

Etymology: Named after the country where the fungus was collected, Oman

Saprobic on dead woods. Sexual morph: Ascomata 130–200 μm high, 180–232 diam (x = 166 × 216 μm), solitary to clustered, superficial, subglobose or nearly globose, ovoid to probably cup-shaped when dry, dark brown to black, carbonaceous, with a blunt ostiole. Peridium 35–70 μm (x = 50 μm, n = 10) wide, comprising two cell types, outer layer composed of small heavily pigmented, thick-walled cells of textura angularis, inner layer composed of lightly pigmented or hyaline, thin-walled cells of textura angularis. Hamathecium of 2–4 μm (x = 3 μm, n= 10), cellular, septate, pseudoparaphyses branching and anastomosing above asci, longer than the asci. Asci 65–95 × 14–18 μm (x = 77 × 15.8 μm, n= 15), 8-spored, bitunicate, fissitunicate, cylindrical to subcylindrical, straight or somewhat curved, with a short, furcate pedicel and minute ocular chamber. Ascospores 10–22 × 6–11 μm (x = 17.2 × 7.5 μm, n = 30), overlapping uni- to biseriate, muriform, initially subclavate to ellipsoid, when mature broadly obvoid or ellipsoid, 3-transseptate, constricted at the central septum, central segments 1–2 longitudinal septate, end cells without septa, pale brown when immature, dark brown at maturity, guttulate, smooth-walled. Asexual morph: Mycelium about 3–4 μm diam, yellow to brown, smooth, septate. Conidiophores solitary, of 2 types; most are longer 150–300 μm, straight to slightly curved, brown, series of 6–12 short, geniculate, sympodial proliferations, shorter conidiophores are up to 100 μm long, commonly with a terminal cluster of 3 conidia. Conidia 9–24 × 4–12 μm (x =15 μm × 8 μm, n=30), conspicuously obovoid and sphaeroid, non-beaked, pale to dark brown, up to 5 transverse and usually 1–2 longitudinal or oblique septa, smooth.

Culture characteristics: Reaching 8 cm within 15 days, white when young, pale brown when mature, umbonate, producing brown to red pigments on media.

Material examined: Sultanate of Oman, Al Jabal al-Akhdar (Green Mountain), dead wood material, 07.2016, SSN Maharachchikumbura OM13 (holotype: SQU H-105) ex-type culture SQUCC 13580 ); ibid., 02.2017, SSN Maharachchikumbura ( OM180 , paratype), (culture SQUCC 15560 ) ; ibid., 02.2017, SSN Maharachchikumbura , culture SQUCC 15561 .

Notes: Alternaria omanensis is phylogenetically related, but distinct from the sections Embellisioides , Eureka and Ulocladium . Sexual morphs are known for A. eureka (= Lewia eureka ); the type species of section Eureka and Alternaria proteae (= Allewia proteae ) in section Embellisioides . Both Alternaria eureka and A. proteae produce an apical beak, and long septate setae from the wall cells of ascomata ( Simmons 1986, 1990). However, the ascomata of A. omanensis are cup-shaped (probably when dry) with a blunt ostiole and lack setae. In addition, the mature ascospores of A. eureka and A. proteae are 5+ transseptate, but only 3–transseptate in A. omanensis . The conidia of section Embellisioides and Eureka are solitary or in short chains, however, conidia of section Omanenses only have solitary conidia. Furthermore, the conidia of section Embellisioides are obovoid to ellipsoid and ellipsoid to cylindrical in section Eureka , whereas conspicuously obovoid and sphaeroid in A. omanensis . The longer conidiophores of A. omanensis has a series of 6–12 short, geniculate, sympodial proliferations, whereas section Ulocladium is characterised by simple conidiophores, or with one or two short, geniculate, sympodial proliferations.

Figures

FIGURE 2. Alternaria omanensis (SQU H-105, holotype) a–b. Ascomata on host substrate. c–d. Section of ascoma (TS). e. Close up of peridium. f–i. Asci with 8-spores. k–j. Muriform, brown ascospores. Scale bars: c, e = 100 μm. f = 25 μm. j, k = 10 μm. Scale bar of c applies to c-d. Scale bar of f applies to f-i.