Gastrodia kachinensis, a new species of Orchidaceae, is described and illustrated from Putao, Kachin State, Myanmar. It is morphologically similar to G. gracilis, presumably its nearest relative, but can be easily distinguished from the latter by having perianth tube with punctate outer surface, verrucose outer surface of sepal lobe, orbicular petals, ovate-elliptic lip with truncate apex and auriculate-clawed base, glabrous lip apex with a pair of twin protuberance-like lamellae and column with a pair of blade-like lateral wings and acute stelidia at apex. Identification key and colour photographs are provided. A preliminary risk-of-extinction assessment, according to the IUCN Red List Categories and Criteria, is given for the new species.

Gastrodieae , Kachin, key, montane forest, taxonomy

Gastrodia R. Brown (1810: 330) (Orchidaceae, Epidendroideae, Gastrodieae) is composed of approximately 90 species, widespread from northeast India through the eastern Himalayas and southern China to Japan and eastern Siberia, southwards to Malaysia and Australia, eastwards to the Pacific Islands as far as Samoa and westwards to Madagascar, Mascarene Islands and tropical Africa (Pridgeon et al. 2005, Chen et al. 2009, Cribb et al. 2010, The Plant List 2013, Chase et al. 2015, Huang et al. 2015, Hsu et al. 2016). It is characterised by a fleshy tuber or coralloid underground stem, absence of leaves, union of sepals and petals and two mealy pollinia with/without caudicles (Dressler 1993, Seidenfaden and Wood 1995, Leou 2000, Chung and Hsu 2006). Although there is no record of Gastrodia in the checklist of Myanmar (Kress et al. 2003), two species of Gastrodia were newly recorded in Myanmar recently (Kurzweil and Lwin 2014, Jin and Kyaw 2017). During fieldwork in Putao, Kachin State, Northern Myanmar, in May 2017, a new species of Gastrodia was discovered and is described below.

All measurements of the new species here described, i.e. Gastrodia kachinensis, were taken from dried herbarium specimens and field notes. In the description, length and width are represented as length × width. About five living plants and four dried specimens of the new species were examined. In addition, all specimens of Gastrodia kept in the Herbarium of Myanmar Forest Department, KUN and PE were examined. Morphological characters of the new species, Gastrodia gracilis Blume and other related species, were based on dried herbarium specimens deposited at the Chinese National Herbarium (PE) and on the high resolution photographs of live plants provided by Tian-Chuan Hsu and Xiao-hua Jin.

Gastrodia kachinensis and G. gracilis are very similar in their vegetative as well as floral morphology. However, Gastrodia kachinensis can be easily distinguished from Gastrodia gracilis by having perianth tube with punctate outer surface, verrucose outer surface of sepal lobe, orbicular petals, ovate-elliptic lip which is orange-yellow towards apex and pale greenish white along each lateral margin and is composed of entire margin, truncate apex, auriculate-clawed base and glabrous adaxial surface with a pair of twin protuberance-like lamellae only at apex and column with a pair of blade-like lateral wings and acute stelidia at apex (Table 1). Gastrodia kachinensis grow at 1400 m in elevation and G. gracilis at ca. 600–1500 m in elevation (Chen et al. 2009). In addition, Gastrodia longitubularis Q.W. Meng, X.Q. Song & Y.B. Luo and G. huapingensis X.Y. Huang, A.Q. Hu & Yan Liu might also be the allied species of Gastrodia kachinensis (Meng et al. 2007, Huang et al. 2015), but G. kachinensis can be easily distinguished from the former two species (Table 1).

Special thanks are due to the Guest Editor Yunhong Tan and two reviewers, Tian-Chuan Hsu and Carlos Leopardi, for their critical and helpful comments on the manuscript. This research was supported by grants from the Southeast Asia Biodiversity Research Institute, Chinese Academy of Sciences (Grant No.Y4ZK111B01) and the National Natural Science Foundation of China (Grant Nos. 31670194, 31110103911). We also thank Yunxi Zhu for the excellent illustration.