Saprobic Dothideomycetes in Thailand: Phaeoseptum hydei sp. nov., a new terrestrial ascomycete in Phaeoseptaceae Author Wanasinghe, Dhanushka N. 0000-0003-1759-3933 Department of Entomology and Plant Pathology, Faculty of Agriculture, Chiang Mai University, Chiang Mai 50200, Thailand & Key Laboratory for Plant Biodiversity and Biogeography of East Asia (KLPB), Kunming Institute of Botany, Chinese Academy of Science, Kunming 650201, Yunnan China. & World Agroforestry, East and Central Asia, 132 Lanhei Road, Kunming 650201, Yunnan, China. & Center for Mountain Futures, Kunming Institute of Botany, Honghe County 654400, Yunnan, China. dnadeeshan@gmail.com Author Mortimer, Peter E. 0000-0003-3188-9327 Key Laboratory for Plant Biodiversity and Biogeography of East Asia (KLPB), Kunming Institute of Botany, Chinese Academy of Science, Kunming 650201, Yunnan China. petermortimer@mac.com Author Senwanna, Chanokned 0000-0002-1008-4514 Department of Entomology and Plant Pathology, Faculty of Agriculture, Chiang Mai University, Chiang Mai 50200, Thailand & Center of Excellence in Fungal Research, Mae Fah Luang University, Chiang Rai, 57100, Thailand chanokned.swn@gmail.com Author Cheewangkoon, Ratchadawan 0000-0001-8576-3696 Department of Entomology and Plant Pathology, Faculty of Agriculture, Chiang Mai University, Chiang Mai 50200, Thailand & Innovative Agriculture Research Center, Faculty of Agriculture, Chiang Mai University, 50200, Thailand. & Center of Excellence in Microbial Diversity and Sustainable Utilization, Chiang Mai University, Chiang Mai, Thailand, 50200. ratcha.222@gmail.com text Phytotaxa 2020 2020-06-18 449 2 149 163 http://dx.doi.org/10.11646/phytotaxa.449.2.3 journal article 303999 10.11646/phytotaxa.449.2.3 02d0e1a2-7de6-4b02-9b41-d8e018fbf392 1179-3163 13877473 Phaeoseptum hydei Wanas., Senwanna & Mortimer , sp. nov . Index Fungorum Number : IF557397, Facesoffungi Number : FoF 07860; FIGURE 2 . Etymology : Named in honour of British mycologist Kevin David Hyde, who celebrates his sixty-fifth birthday and for his innumerable contributions to ascomycete taxonomy. Saprobic on dead twigs in terrestrial habitats. Sexual morph : Ascomata 350–500 μm high, 300–380 μm diam. (x̅ = 411.4 × 323.6 µm, n = 10), scattered to gregarious, fully immersed under a small blackened pseudoclypeus, appearing as black, elongated regions on host surface; ascomata depressed spherical, laterally flattened. Pseudoclypeus composed of host cells with black deposits. Peridium 8–20(–40 at apex) µm wide, pseudoparenchymatous, of thinwalled cells, at apex comprising isodiametric angular cells that are more pigmented outwardly, at sides with flattened hyaline cells, at base of angular pigmented cells. Hamathecium comprising 1.5–2.5 μm (n = 20), wide septate, cellular pseudoparaphyses, situated between and above the asci, embedded in a gelatinous matrix. Asci 110–180 × 20–30 μm (x̅ = 141.5 × 36.5 μm, n = 30), 8-spored, bitunicate, fissitunicate, cylindrical-clavate, with a distinct pedicel (30–45 μm long; x̅ = 35.9 μm, n = 30), apically rounded with a minute ocular chamber. Ascospores 20–25 × 6–7 μm (x̅ = 22.3 × 6.4 μm, n = 50), uniseriate at base and overlapping 3–4-seriate at apex, pale to dark brown, broadly fusoid with broadly rounded ends, slightly curved, 7–9-transversally septate, with a vertical septum in nearly all median cells, not constricted at the septa, the septa partly pale brown, having at maturity a thickened and heavily pigmented appearance, wall smooth, without sheath or appendages. Asexual morph : Undetermined. Culture characteristics : Colonies on PDA reaching 4 cm diam. after 30 days at 25°C, circulate in shape, smooth margin, from above dark brown, dense, flattened, umbonate, fairly fluffy, reverse greenish grey. Hyphae septate branched, hyaline, thin, smooth-walled. Known distribution : Thailand , on dead twigs of Delonix regia (Boj. ex Hook.) Raf. Material examined : Thailand , Chiang Mai , Mueang Chiang Mai District , Suthep, Chiang Mai University, 18.794368N , 98.959904E , on a dead twig of Delonix regia ( Fabaceae ), 15 February 2017 , Chanokned Senwanna DHA17-1 (MFLU 17-0660, holotype ) , ex-type living culture, MFLUCC 17-0801. Notes : Phaeoseptum hydei was found on a dead twig of Delonix regia from Chiang Mai , Thailand . Its morphology comparable with the type species of the genus Phaeoseptum , P . aquaticum , and other species in Phaeoseptum in having fully immersed ascomata under a small blackened pseudoclypeus, cylindrical-clavate asci with a distinct pedicel and broadly fusoid, brown ascospores with multi-transverse septa. The phylogenetic analyses of a combined sequence data-set (LSU, SSU, ITS and TEF) positions our novel species, Phaeoseptum hydei (MFLUCC 17-0801) with other remaining taxa in Phaeoseptum (Clade A) with strong statistical support (100 % ML, MP and 1.00 PP, Fig. 1 ). The phylogeny shows Phaeoseptum hydei is basal to Phaeoseptum species with close affinity to P . terricola (MFLUCC 10-0102). Morphologically, Phaeoseptum terricola differs from P . hydei in having 8-spored and comparatively small asci (64–90 × 13–17.5 μm) whereas P . hydei has 32-spored asci that are larger (110–180 × 20–30 μm). Phaeoseptum terricola also has a relatively smaller (137–214 high × 155–224 diam.) ascomata compared with P . hydei (350–500 high × 300–380 diam.). The 32-spored asci is a unique characteristic for all sampled fruiting bodies of the holotype and this feature has not seen any of the other species in Phaeoseptum ( Table 2 ).