Digitaria isanensis B. Boonsuk, Chantar. & Hodk. (2014b)

Boonsuk, Boonchuang, Chantaranothai, Pranom & Hodkinson Abstract, Trevor R., 2016, A taxonomic revision of the genus Digitaria (Panicoideae: Poaceae) in mainland Southeast Asia, Phytotaxa 246 (4), pp. 248-280 : 260

9. Digitaria isanensis B. Boonsuk, Chantar. & Hodk. (2014b) . Type:— THAILAND, Kalasin, Yang Talat, Hua Na Kham , B. Boonsuk 430 (holotype KKU!; isotypes BK!, BKF!, K!, QBG!).

Annual. Culms stoloniferous, decumbent, 10–30 cm high; nodes glabrous, rooting at lower nodes; internodes glabrous. Sheath s pilose or glabrous, 1–3 cm long. Blades lanceolate, 1.5–4 by 2–4 mm, apex acuminate, both surfaces sparsely pilose or glabrous. Ligules 0.4–0.6 mm long. Inflorescences a solitary raceme or composed a few racemes; peduncles glabrous; common axis absent. Racemes 1–3, usually 1, longest 2.5–6 cm long, digitate; rachis ribbon-like, winged, 0.7–0.9 mm wide, serrate. Pedicels terete with spicules; abscission cupuliform. Spikelets ternate, homomorphous, elliptic, 2.1–2.3 mm long; hairs verrucose with acute apex. Lower glume 0.1–0.2 mm, membranous, apex truncate. Upper glume elliptic, as long as the spikelet, chartaceous, apex acute, pubescent between the nerves, nerves 7. Lower lemma as long as the spikelet, chartaceous, apex acute, pubescent with narrow glabrous interspaces beside the midnerve, nerves 7, inequidistant. Upper lemma slightly shorter than spikelet, chartaceous to coriaceous, apex acuminate, yellowish. Anthers 0.5–0.7 mm long, reddish brown. Caryopsis ellipsoid, 1.4–1.6 mm long, creamy.

Distribution: — Thailand, Cambodia.

Selected specimens examined: — CAMBODIA. Kampong Cham: July 1921 A. Pételot 241 (P). THAILAND. Udon Thani:Phu Foi Lom Forest Park, 8 September 2012, B. Boonsuk 632 (BK, BKF, KKU, QBG). Nakhon Ratchasima: Bua Yai, 28 July 2008, M. Norsaengsri 3990 (QBG). Yasothon: Phu Sa Dok Bua National Pak, 30 May 2010, B. Boonsuk 253 (KKU). Ubon Ratchathani: Sirindhorn, 26 July 2010, B. Boonsuk 345 (BK, BKF, KKU, QBG).

Ecology: —Sandy soils in open areas; elevation 150– 500 m.

Conservation status: — Digitaria isanensis is known from specimens from the northeast of Thailand and one specimen from Cambodia. Its conservation status is assessed as Data Deficient (DD) according to IUCN (2012) criteria.

Note: — Digitaria isanensis is similar to D. petelotii but differs in its smaller habit, its smooth internodes and its single raceme. We here report the first occurrence of this species for Cambodia.