Urochloa distachyos (L.) T.Q. Nguyen

Vorontsova, Maria S., 2022, Revision of some Malagasy forage grasses and their relatives within Brachiaria, Echinochloa, Moorochloa, and Urochloa, Candollea 77 (2), pp. 199-236 : 226

19. Urochloa distachyos (L.) T.Q. Nguyen in Novosti Sist. Vyssh. Rast. 1966: 13. 1966 (F ig. 14C–D).

Panicum distachyon L., Mant. Pl.: 183. 1767. Brachiaria distachyos (L.) Stapf in Oliv., F l. Trop. Afr. 9: 565. 1919.

Lectotypus (designated by HENRARD 1950: 191): INDIA: “Habitat in India orientali. Koenig.”, s.d., Herb. Linn. No. 80.41 ( LINN-HL80-41 image!) .

= Panicum subquadriparum Trin., Gram. Panic. : 145. 1826. Brachiaria subquadripara (Trin.) Hitchc. in Lingnan Sci. J. 7: 214. 1931. Urochloa subquadripara (Trin.) R. D. Webster, Austral. Paniceae ( Poaceae ) 252. 1987. Lectotypus (designated by SOSEF, 2016: 360): GUAM: sine loco, s.d., Chamisso in Herb. Trinius 0974.01 ( LE) .

= Panicum miliiforme J. Presl in C.B. Presl, Reliq. Haenk. 1: 300. 1830. Brachiaria miliiformis (J. Presl) Chase in Contr. U.S. Natl. Herb. 22: 35. 1920. Brachiaria subquadripara var. miliiformis (J. Presl) S.L. Chen & Y.X. Jin in Acta Phytotax. Sin. 22: 472. 1984. Holotypus: PHILIPPINES. Luzon: sine loco, s.d., Haenke s.n. (PR; iso-: B [B 10 0367348] image!, HAL [HAL0063364] image!, W [W18890237977, W0006077, W0006079] images!).

Stoloniferous mat-forming perennial, prostrate with ascending flowering culms, ascending to c. 0.5 m high, culms branched, rooting at lower nodes, often with a knotty rootstock, glabrous. Leaf sheath glabrous or sparsely pubescent with ciliate margins. Ligule a ciliate membrane. Leaf blade linear to narrow-lanceolate, chartaceous, 2–20 × 0.3–1 cm, glabrous to sparsely pubescent on both sides. Inflorescence racemose, slender, open, 3.5 – 15 cm long, peduncle glabrous to pubescent. Racemes 2–5, 1–6 cm long, gently curved, roughly even in length, on a common axis 0.5–10 cm long, with no secondary branching, rhachis narrowly winged, 0.7–1 mm wide, scaberulous, spikelets imbricate, single, subsessile, in 2 rows. Spikelets plump elliptic to obovate, apically subacute to acute, 2.5–3.7 mm long, whiteish, sometimes tinged with purple. Lower glume ⅓–½ as long as spikelet, membranous, clasping, obtuse, 5–7-veined, glabrous, separated from rest of spikelet by an internode c. 0.5 mm long, turned towards rhachis. Upper glume as long or almost as long as spikelet, membranous, 5–7-veined, glabrous. Lower floret infertile, palea ⅔ as long to almost as long as lemma. Lower lemma membranous, 5-veined, glabrous. Upper lemma subobtuse to acute, rugulose.

Distribution and ecology. – Paleotropical forage and adventitious grass common in the warmer lowland parts of Madagascar, and especially common the far north of Madagascar and on Nosy Be. Roadsides, rice paddies and fields of maize and sugarcane, savannas, costal habitats especially on sand, at elevations of 0–600 m (F ig. 13).

Notes. – Urochloa distachyos is a known invasive tropical lawn and pasture weed with creeping stolons, typically invading rice paddies and pastures at lower elevations. It seems to be related to U. arrecta (HACKEL et al., 2018), which is abundant across the highlands.

This treatment follows SOSEF (2016) and MORRONE & ZULOAGA (1992) in treating Urochloa distachyos as conspecific with U. subquadripara (Trin.) R.D. Webster, as part of a possible polyploid complex. BOSSER (1969) considered the northern populations previously assigned to Brachiaria subquadripara (Trin.) Hitchc. [ B. miliiformis (J. Presl) Chase in BOSSER (1969)] with longer spikelets to be recent introductions, making no statement on the origin of the B. distachyos with shorter spikelets in southern and western Madagascar.

Selected specimens examined. – MADAGASCAR. Reg. Androy [Prov. Toliara]: Ambovombe Sud, I.1956, Descoings 1577 ( P); Andasaria, 20 km before Tsihombe village on the RN 13, 18.III.2019 , Rakotomalala et al. 307 ( K, TAN). Reg. Atsinanana [Prov. Toamasina]: Tamatave, 13.VII.1964, Tateoka 3587 ( P). Reg. Boeny [Prov. Mahajanga]: Bealoy, VI.1953, Bosser 5468 ( P); 5–10 km before Ambondromamy , before Kamoro bridge, 13.II.2013, Vorontsova et al. 915 ( K, TAN). Reg. AIANA [Prov. Antsiranana]: Ambavahibe , Montagne d’Ambre, VII.1953, Bosser 5515 ( K, P); Nosy-Be , Ambatoloaka , VIII.1959, Bosser 13222 ( P); Ambilobe , Sosumav, XII.1964, Morat 1284 ( P); from Cape Ste Marie ANGAP office on the road to Soamanitra, 28.IV.2014, Vorontsova et al. 1432 ( P, TAN) .