Chaetothyrina guttulata Hongsanan & K.D. Hyde, sp. nov.
Index Fungorum number: IF551933
Etymology: guttulata referring to the ascospores which have 2-guttules in each cell.
Epiphytes appearing as small black dots on the surface of branches of Mangifera indica. Thallus very thin, especially around the thyriothecia, covering surface of host with dark brown hyphae. Superficial hyphae 3 μm wide, septate, not constricted at the septum, branched, brown to dark brown, not dense. Sexual morph: Thyriothecia 175–185 x 47–56 µm (x=180 x 52 µm, n=5), superficial, solitary, circular, flattened, base poorly developed, thin-walled, brown to dark brown, rounded, easily removed from host surface, central ostiole present at maturity, thyriothecial setae present, but poorly developed. Setae 60−85 µm long (x=76 μm, n=10), arising from the surface of thyriothecia, straight, unbranched, septate, brown to dark brown, darkened at the septa, hyaline at the apex, smooth-walled. Ostiole 28–31 µm diam. (x=30 µm, n=5), comprising subcylindrical cells, light brown. Upper wall comprising 2−3 layers, inner layer hyaline, outer layer dark brown of cells of textura epidermoidea. Peridium 10–14 μm (x=11 μm, n=10), comprising cells of textura angularis or flattened cells, inner layer hyaline, outer layer dark brown or reddish brown. Hamathecium of 2 µm wide, septate, hyaline, pseudoparaphyses. Asci 32–37 x 12–14 µm (x=35 x13 µm, n=10), 8-spored, bitunicate, subcylindrical to obovoid, short pedicellate or sometimes apedicellate, ocular chamber long when immature. Ascospores14–16 x 4–5 µm (x=15 x 4.5 µm, n=10), bi to tri-seriate, ellipsoid, 1-septate, constricted at the septum, upper cell wider than lower cell, tapering towards the base, hyaline, with 2 guttules in each cell. Asexual morph: Undetermined.
Culture characteristics: Ascospore germinating on PDA at 25–28 °C for 12 h of light/12 h of dark, hyphae germinating from both cells of the ascospore, septate, not constricted and slightly darkened at the septum, hyaline to grayish initially, and become dark grey to black later, darker at the center. Colonies slow growing, reaching 2 cm diam. after 5 days on PDA, colony superficial to erumpent, surface smooth, velvety.
Material examined: THAILAND. Chiang Rai Province: Tasud, Ban Doo, Pong Phra Bat, on branches of Mangifera indica, 13 September 2015, S. Hongsanan, MM03 (MFLU16-0299, holotype); ibid. (isotype in KUN), ex-type living culture, MFLUCC15-1081; THAILAND. Chiang Rai Province: Tasud, Ban Doo, CRU, on branches of Mangifera indica, 13 September 2015, S. Hongsanan, MM02 (MFLU16-0256), living culture, MFLUCC 15-1080.
Fig. 3. Chaetothyrina guttulata. (holotype) a Young budding shoot of mango with small black dots of thyriothecia; b, c Thyriothecia on the surface of young budding shoot of mango; d Thyriothecium when viewed in squash mount; e Section through thyriothecium; f Thyriothecial setae; g Hamathecium; h Ostiole; i Ascus; j Ascus in Melzer’s reagent; k, l Ascospores with 2-guttules; m Germinated ascospore. Scale bars: d, e=50 µm, f−h, k−m=10 µm, i, j=20 µm.
