Corynesporopsis ponciri G. Delgado & Koukol, 2023

Delgado, Gregorio, Koukol, Ondřej & Colbert, William, 2023, Texas microfungi: a new species of Corynesporopsis (Xylariales) associated with the trifoliate orange, Phytotaxa 607 (1), pp. 8-22 : 14-18

Corynesporopsis ponciri G. Delgado & Koukol , sp. nov. ( Figs 3 , 4 )

MycoBank MB848526

Etymology. ponciri , referring to the host genus Poncirus , the trifoliate orange, from which the fungus was isolated.

Description. Colonies on natural substrate black,either punctiform at first or effuse,later caespitose,hairy,becoming confluent and extending to form large superficial patches covering almost entirely the surface of twigs, branches, and thorns of the host, easily detaching and carrying away the cuticular wax. Mycelium partly immersed, substomatal or subcuticular, and partly superficial on the substratum, composed of unbranched, septate, subhyaline to pale brown or brown, smooth hyphae, 2–3 µm wide. Stromata present, in the form of stromatic hyphal aggregations, dense, compact, substomatal, subcuticular, dark brown to blackish brown. Conidiophores macronematous, mononematous, unbranched, solitary or fasciculate, erect, straight to flexuous, cylindrical, brown, 2–7-septate, smooth to verruculose, up to 76 µm long, 6–8 µm wide, 3–5 µm wide at the apex, 8–10 µm wide at base, arising from substomatal stromata in small to moderately large fascicles, loose or somewhat dense. Conidiogenous cells monotretic, integrated, terminal, mostly determinate, rarely percurrent, cylindrical, subcylindrical or narrowly doliiform, smooth or verruculose, often thickwalled around the conidiogenous locus and slightly attenuated to a truncate end, percurrent proliferations when present 0–1-septate, 13–21 × 7–8(–10) µm. Conidia acrogenous, ellipsoidal or fusiform to naviculiform, straight or sometimes curved, smooth or verruculose, brown, concolorous or not, often with the apical cell light brown, euseptate, with 2, rarely 1 or 3 septa, usually with an associated dark band, slightly constricted at the septa or not, (17–)22–39(–42) × (7–)8–9(–10) µm, basal scars conspicuous, thickened and darkened, broad, (3–)4–6 µm wide, 2–4(–5) µm wide at the apex, solitary or catenate, in short, unbranched, acropetal chains of up to four, each successive conidium emerging through a pore at the terminal conidium, sometimes thickened or darkened.

Culture characteristics. Colonies on MEA moderately slow growing, reaching 20–22 mm diam. after 4 weeks at 25°C, velvety, brown, dark brown toward the edge, flat but raised and somewhat cottony at the center due to the presence of dark brown hyphal ropes or funicles, zonate with 1-2 concentric rings of growth, margin somewhat undulose, reverse blackish brown, releasing a dark amber diffusible pigment into the medium, no sporulation and remaining sterile after three months.

Type. UNITED STATES. Texas: The Woodlands, George Mitchell Nature Preserve , along the Wood Duck Loop , 30°08’51.7”N 95°30’49.1”W, on dead twig of Poncirus trifoliata (L.) Raf. ( Rutaceae ), 15 May 2022, G. Delgado (holotype BPI 911238 , ex-type living culture CBS 149522) .

Additional specimens examined. UNITED STATES. Texas, The Woodlands, George Mitchell Nature Preserve, along the Crossover Trail, 30°09’13.8”N 95°31’04.0”W, on hanging dead twig of P. trifoliata , 14 May 2022, G. Delgado ( BPI 911235, CBS 149520; BPI 911236, CBS 149521).—Ibid., along the Main Trail between the Horned Owl Loop and Wood Duck Loop, 30°08’53.9”N 95°30’52.1”W, on dead branches of P. trifoliata , 15 May 2022, G. Delgado ( BPI 911237, CBS 149259). Corynesporopsis biseptata (M.B. Ellis) Morgan-Jones (as Corynespora biseptata ). UNITED KINGDOM. England, Sussex, on dead wood, 22 May 1959, M. B. Ellis ( AUA 2593 = IMI 76701, holotype). Corynesporopsis isabelicae Hol. -Jech. NICARAGUA. Rio San Juan, San Juan de Nicaragua, Indian River near Greytown, on dead bamboo culms, C. L. Smith, March 1893 ( PRC 674).

Notes. Among species of Corynesporopsis with 2-septate conidia, C. ponciri is comparable with C. biseptata and C. quercicola (Borowska) P.M. Kirk. An examination of the type material of C. biseptata , however, confirmed it is morphologically different in having cylindrical, straight, obtuse at each end and pale brown to brown conidia, lacking any distinct basal scar and with the central cell usually slightly longer that the end cells ( Morgan-Jones, 1988). Corynesporopsis quercicola , on the other hand, differs in having smaller conidia, (12) 14–22 × 6–8 (9) µm, rounded at each end, with end cells pale brown and middle cell dark brown ( Borowska 1975). Other two species, C. isabelicae and C. liquidambaris Jian Ma & X.G. Zhang , somewhat resemble C. ponciri in having similarly shaped conidia with a broad basal scar and septa with an associated dark band, but their conidia are narrower or smaller and consistently 1-septate ( Holubová-Jechová 1987, Ma et al. 2012a). A comparison with a specimen of C. isabelicae collected in Nicaragua ( Delgado & Koukol 2016) confirmed these differences.

Figures

FIGURE 3. Corynesporopsis ponciri (BPI 911238, holotype). a–b. Branches of Poncirus trifoliata still attached to the trees showing symptoms of colonization. c–d. Colonies on MEA (after 4 wk at 25 °C) on surface and reverse view. e–f. Conidiophores, conidiogenous cells and conidia. g. Apical loci of conidiogenous cells showing channel-like pores (indicated by black arrows) and conidia. h–i. Conidia in chains. j. Conidiogenous cells in lateral view showing the attenuated and flat apical loci. Scale bars: e–f, h–i = 20 µm; g, j = 10 µm.

FIGURE 4. SEM micrographs of Corynesporopsis ponciri (BPI 911238, holotype). a. Loose fascicles of conidiophores on the surface of the host. b. Conidiophore with chain of conidia. c. Conidiophores emerging from substomatal stroma. d.Apex of conidium showing apical pore. Scale bars: a = 20 µm; b–c = 10 µm; d = 2 µm.