Curcuma achrae Saensouk & Boonma, 2022

S., Saensouk, T., Boonma & Saensouk, P., 2022, Curcuma achrae (Zingiberaceae), a new species from Central Thailand, Rheedea 32 (1), pp. 30-45 : 31-37

publication ID	https://doi.org/10.22244/rheedea.2022.32.01.03
DOI	https://doi.org/10.5281/zenodo.16902451
persistent identifier	https://treatment.plazi.org/id/6F2D87C2-180B-D649-2B58-C8D96503FD07
treatment provided by	Felipe
scientific name	Curcuma achrae Saensouk & Boonma
status	sp. nov.

Treatment

Curcuma achrae Saensouk & Boonma View in CoL , sp. nov. Figs. 1–5 View Fig View Fig View Fig View Fig View Fig

Similar to Curcuma xanthella Škornik. but differs. C. achrae having pubescent petioles ( vs. glabrous), green with a reddish tinge ( vs. green); adaxially sparsely hairy leaves with fine hairs along the midrib ( vs. glabrous on both surfaces); fertile bracts connate in the lower 1/7 ( vs. connate in the lower 1/4), apex mucronate ( vs. narrowly acute); base of labellum white, middle and apical part golden yellow, with embossed two golden yellow median band running along the midrib from tip to base and divided into two Y-shaped patches at base ( vs. base of labellum white to light yellow, middle and apical part warm yellow, with two yellow-orange swollen bars running across the center); staminodes irregularly ovate, apex acute, golden yellow gradually fades to pale yellow at base, with reddish V-shaped or triangle patch at base of staminodes ( vs. staminodes irregularly oblong, apex obtuse, bright warm yellow without red patch); anther appear almost straight ( vs. anther appear as L-shaped), spurs c. 3 mm long ( vs. spurs c. 6 mm long), crest 3–4 mm long with apex acute to rounded or slightly truncate ( vs. crest not obvious).

Type: THAILAND, Nakhon Nayok province, Mueang Nakhon Nayok district, 60–152 m, 05.04.2021, T. Boonma 24 ( holo KKU!; iso QBG!, BKF!, BK!) .

Perennial herbs, up to 45 cm tall. Rhizome ovoid, 3.2–3.8 × 1–1.4 cm, brown externally, two layers of pale yellow internally, fragrant; root tubers ellipsoid, 2.5–3 × 1.2–1.4 cm, brown externally, white internally, fragrant, developing some distance from the rhizome. Leafy shoot with 6–8 leaves spread out in a circle parallel to the ground almost the same plane, developing after flowering; pseudostem 18–24 cm long, green with reddish brown tinge, composed of sheathing bracts and leaf sheaths; sheathing bracts 2–3, apex slightly mucronate, reddish when young with green tip and drying out and decaying while growing; leaf sheaths distichous, green with reddish brown tinge, pubescent; ligules up to 6 mm long, bilobed, hyaline, green with a reddish tinge, sparsely hairy; petioles up to 25 cm long (petiole of innermost leaves longest, outermost leaf shortest), canaliculate, green with a reddish brown tinge, pubescent; lamina narrowly ovate to narrowly elliptic, 26–45 × 10–13 cm, base cordate, margins slightly undulate, apex caudate, adaxially green, sparsely hairy, abaxially lighter green, puberulous, midrib green or brownish green, with fine hairs along the midrib, spread out into a circle shape, almost in the same plane parallel to the ground. Inflorescence lateral, peduncle and base of the spike often subterranean; peduncles 3–5 cm long, with up to 6 mm diam., white, pubescent, with up to 6 sheathing bracts (sheathing bracts red or reddish tinge with white at base, apex mucronate, pubescent); spike 4–6.5 cm long, 2–3 cm diam. in the middle, wider apically, coma absent; fertile bracts 10–18, narrowly ovate to lanceolate, smaller and narrowly ovate at the apex, 2.5–5.8 × 1–2.5 cm (larger at the base of the inflorescence), apex mucronate, both sides pubescent, pale green with various degrees of reddish tinge, connate in the lower 1/7; cincinni with 3–4 flowers at the base of the inflorescence, 1–2 flowers at the top; bracteoles one per flower, narrowly triangular, 7–12 × 1–2.7 mm (outer ones larger, inner ones are gradually smaller), pubescent, translucent white. Flowers 5.8–6.4 cm long; calyx tubular, 18–20 mm long, 3-toothed, with unilateral incision up to 8 mm long, pubescent, translucent white; floral tube 30–32 mm long, externally yellowish white with pale pink tinge, pubescent, white internally, with white hairy at throat; dorsal corolla lobe narrowly triangular ovate, 21–26 × 9– 11 mm, concave, sparsely hairy, apex mucronate, 3.3–4.8 mm long, sparsely hairy, pale yellowish white at base, yellowish with pale pink tinge towards the apex; lateral corolla lobes narrowly triangular-ovate; 18–24 × 7–9 mm, concave, apex slightly mucronate, sparsely hairy, pale yellowish white at base, yellowish with pale pink tinge towards the apex; labellum obovate, 27–29 × 18– 20 mm, apex emarginate, incision to 7 mm, base of labellum white, middle and apical part golden yellow, with embossed two golden yellow swollen bars running along the midrib from tip to base and divided into two patches at base like a Y-shape (forming a median band), fine and short hairy along both sides of median band; lateral staminodes irregularly ovate, 24–26 × 14–17 mm, apex acute, with short fine hairy on the adaxial side, golden yellow gradually fades to pale yellow at base, with reddish V-shaped or forming of triangle patch at base of staminodes. Stamen 12–14 mm long; filament 4–5 mm long, pale yellowish-white, c. 5 mm broad at the base, c. 3 mm broad at the apex (the point of attachment to the connective), covered with short fine hairs; anther 12.5–14 mm long (measured in side-view including spurs and crest), yellowish, spurred, pubescent; connective yellowish-white, covered with short fine hairs; anther spurs c. 3 mm long, conical, pale yellow, covered with transparent jelly on both spurs, pointing outwards; anther crest 3–4 mm long, 2.7– 3 mm wide, golden yellow, apex acute to rounded or slightly truncate, rarely retuse, covered with short fine hairs; anther thecae 6.5–7 mm long. Epigynous glands two, 5–7 mm long, 0.7–0.8 mm across, pale yellow, apex acute. Style thin, white, glabrous, placed in the groove in the dorsal side of floral tube; stigma c. 1.7 × 1.8 mm, pale yellow; ostiole ciliate. Ovary c. 3.8 × 3 mm, trilocular, puberulent. Fruits and seeds not seen.

Vernacular name: Khamin Thong.

Flowering & fruiting: Flowering from late March to early May; flowers open in the morning and last a single day. Leafy shoot emerging in late May and dormancy begins in November. Fruiting was not observed.

Habitat: Occurring at elevations of 60–152 m, growing in sandy loam soil at the boundary, close to the watercourse, in semi-open area in a deciduous forest.

Distribution: Curcuma achrae is known from the southwestern part of the Sankamphaeng mountain range in Mueang Nakhon Nayok district, Nakhon Nayok province, Central Thailand ( Fig. 4 View Fig ).

Etymology: The specific epithet “ achrae ” is chosen to honour Assistant Professor Dr. Achra Thammathaworn (botanist of Khonkaen University), who is a specialist in botany and teacher of many Thai botanists.

Specimens examined: Curcuma xanthella Škornièk. : VIETNAM, Bình Thu-n province, Hàm Thu-n Nam district, Tà Kóu Nature Reserve , 145 m, 11.06.2009, LÝ 348 ( holo SING; iso E, VNM); Tà Kóu mountain, 30.05.2009, Nguy n Thi n T ch (under Tr n collection number), Tr n 158 ( E, SING, incl. spirit). Lâm ÐÓng province, Bào Lôc pass, 22.06.2008, Tr n et al. s.n. (collected from cultivation, 06.05.2013), GRC-147 ( SING, incl. spirit) .

Curcuma flaviflora S.Q.Tong : CHINA, Yunnan australis, Menhai Xian , 1400 m, S.Q.Tong & A.M. Li 32855 ( holo YNTBI). THAILAND, Chiang Mai province, Doi Angkang, Fang , 12.06.1999, Srisanga 721 ( QBG). Ibid., 21.07.2003, Maknoi 356 ( AAU, PSU, QBG). Ibid., 15.05.2004, Maknoi 535 ( AAU, PSU, QBG). Chiang Dao , Norsaengsri 1476 ( QBG). Doi Pui, Huai Hi , Mueang , 25.07.2003, Maknoi 382 ( AAU, PSU, QBG). Khun Huai Mae Kok, 05.06.2001, Wongprasert 015-05 ( BKF). Mae Hong Son province, 15 km N.W. of Mae Hong Son , 18.06.1973, Geesink, Panichapol & Santisuk 5960 ( C, E).

Conservation status: This new species is hitherto known from the type locality in Nakhon Nayok province, Central Thailand (the Southwest part of the Sankamphaeng mountain range ). Available information about this species is insufficient for a proper assessment of its conservation status. Thus according to IUCN criteria ( IUCN, 2022) it should be listed as Data Deficient (DD). However , we expect this plant to be found distributed elsewhere in the Sankamphaeng mountain range and nearby in the Khao Yai National Park where suitable habitats still seems to exist. Further fieldwork and observations are needed to assess changes in population, distribution, and abundance of this taxon in the future.

Notes: Curcuma achrae belongs to subgen. Ecomata ( Záveská et al., 2012) because of the absence of a coma bract, open-form flower, presence of epigynous glands, and conical anther spur. This species has varied size and colour of bracts but produces almost the same size of flowers ( Fig. 2d View Fig ).

Curcuma achrae is similar to C. flaviflora S.Q.Tong , C. aruna Maknoi & Saensouk , and C. xanthella Škornièk. in having yellow flowers, an inflorescence produced directly from the rhizome before the new leaves, lacking coma bracts, open flowers, and presence of epigynous glands. Curcuma flaviflora is a high-elevation species known to occur in pine forests in the mountains of northern Thailand and southern China. Curcuma aruna occurs in scrub forests at foothills of limestone mountains and is currently only found in Sukhothai province in northern Thailand, while C. xanthella is so far recorded from two places in southern Vietnam and differs from C. achrae by many characteristics e.g., shape and surfaces of leaves, and different shapes, colors, sizes, and proportions of various flower parts, especially in having an Lshaped anther whereas in C. achrae it is almost straight. The morphological comparison of C. achrae with its allied species C. xanthella and C. flaviflora is provided in table 1. A comparison of anthers in front and side view, and flowers of the newly described species and its similar species are additionally provided in figure 5. A key to the species of Curcuma distributed in Thailand and a revised key to species of Curcuma subgen. Ecomata are provided for facilitating their identification in the field.