Diaporthe siamensis Udayanga et al., Cryptogamie Mycologie 33: 298 (2012)

Saprobic on dead leaves of woody plants. Sexual morph Undetermined. Asexual morph Conidiomata pycnidial,
185–200 μm high, 150–200 μm diam. (x = 190 x 170 μm, n = 10), ampulliform, scattered, immersed, ostiolate, with elongate black neck. Pycnidial wall, comprising 2–3 layers, with heavily pigmented outer layer, thick-walled, comprising blackish to dark brown cells of textura angularis, with lighter cells towards the inside, with inner layer composed of 1–2 layers, hyaline, thin-walled cells of textura angularis. Conidiophores reduced to conidiogenous cells. Conidiogenous cells enteroblastic with percurrent annellations, integrated, solitary, hyaline, smooth-walled and formed from the inner layer of pycnidium wall. Paraphyses extending above conidiophores and hyaline, 20–35 lm long. Alpha conidia 3–5 x 2–3 μm (x = 3.5 x 2.4 μm, n = 30), hyaline, smoothwalled, mono- or bi-guttulate. Beta conidia1 5–20 x 1.5–2 μm (x = 18.5 x 1.8 μm, n = 30), aseptate, hyaline, hamate or curved, apex acutely rounded.

Culture characteristics: Colonies on PDA 30 mm diam. after 4 weeks at 25 ºC, cream to white mycelium, cottony and lobate at the margins, white at the center; reverse yellowish. Material examined: THAILAND, Chiang Rai Province, Thasud, Muang District, Mae Fah Luang University, on dead leaves of Castanopsis sp. (Fagaceae), 21 March 2012, N. Tangthirasunun (MFLU 13-0257, NTCL056-1), living culture, MFLUCC 12-0300.

Notes: Diaporthe siamensis was introduced by Udayanga et al. (2012). This species was described on leaves of Dasymaschalon sp. (Annonaceae) from Chiang Rai, Thailand. Since then this species has not been reported from any locality worldwide. Here we have collected D. siamensis for the first time on Castanopsis sp. (Fagaceae) from a close locality in Thailand. The morphological characters are similar to the type specimen. Based on the phylogenetic analysis of combined ITS, EF1-a, CAL sequence data, shows high support to its ex-type strain MFLUCC 10-0573a, clusters with high support with D. siamensis MFLUCC 12-0300. According to Udayanga et al. (2012) this species was found in different habitats of Dasymaschalon sp. whereas, in this study we isolated it as a saprobic fungus. Identification of D. siamensis, within the same locality on two different plant groups, reveals the potential of this species to occur on multiple hosts in different habitats.

Fig. Diaporthe siamensis (MFLUCC 12-0300, NTCL056-1). a Herbarium specimen. b Appearance of conidiomata on the host surface. c Vertical section of conidioma. d Peridium. e Ostiole. f, g Conidiogenous cells with developing conidia. h Alpha conidia. i Beta conidium. j Germinating alpha conidium. k–l Culture on PDA, k top, l reverse. Scale bars b = 500 lm, c, d = 100 lm, e = 50 lm, f–j = 10 lm