DNA barcoding of the recently evolved genus Holcoglossum (Orchidaceae: Aeridinae): a test of DNA barcode candidates

Orchidaceae is one of the largest families of flowering plants. Many species of orchid are endangered, and all species are included in Conventions on International Trade of Endangered Species of Fauna and Flora (CITES) I and II, but it is very difficult to identify orchid species, even those with fertile parts. The genus Holcoglossum (Orchidaceae: Aeridinae) has long been problematic in taxonomy. It consists of both long-evolved and radiated species and is an excellent case to use for testing DNA barcodes for Orchidaceae. We investigated the power of a subset of proposed plant barcoding loci [rbcL, matK, atpF-atpH, psbK-psbI, trnH-psbA and internal transcribed spacer (ITS)] to discriminate between species in this genus. Our results showed that all these DNA regions, except psbK-psbI and atpF-atpH, can be amplified easily from Holcoglossum and sequenced with established primers. The DNA regions matK and ITS had the highest variability. Among the six loci, matK resolved eight of the 12 Holcoglossum species and had the highest discriminatory ability. However, the combination of matK and ITS showed a greater ability to identify species than matK alone. Single or combined DNA markers discriminated between Holcoglossum species distributed in tropical areas effectively, but had less ability to identify radiated species from the temperate Hengduan Mountains of China. In the study, matK proved to be a useful DNA barcode for the genus Holcoglossum; however, complementary DNA regions are still required to accelerate the investigation and preservation of radiated species of orchid.     

Pollination system of Holcoglossum rupestre (Orchidaceae): A special and unstable system

The pollination system of Holcoglossum rupestre was studied in northwestern Yunnan. The species is self-compatible but pollinator-dependent and offers nectar as a reward to visitors. A species of beetle, Hybovalgus bioculatus Kolbe, is identified as the pollinator among all visitors observed. The beetles carried the pollinia in two different positions, i.e. on the buttock and the foreleg, and pollinated the flowers by two different mechanisms. The analysis suggests that Holcoglossum rupestre and its pollinator may be in an unstable pollination relationship. The natural fruit set is low, which is attributed to the low visiting frequency of pollinator and the effective mechanism to prevent self-pollination.     

Generic delimitation and a new infrageneric system in the genus Holcoglossum (Orchidaceae: Aeridinae)

Based on herbarium and field observations, we confirm the generic delimitation of Holcoglossum and present a new infrageneric system for the genus. Our work supports Holcoglossum as a natural group including H. amesianum (Rchb.f.) Christenson and H. subulifolium (Rchb.f.) Christenson. The new infrageneric system of Holcoglossum includes two subgenera: Holcoglossum subgen. Brachycentron subgen. nov. and Holcoglossum subgen. Holcoglossum , the latter comprising two new sections, Holcoglossum sect. Holcoglossum and Holcoglossum sect. Sorotylos .  © 2005 The Linnean Society of London, Botanical Journal of the Linnean Society , 2005, 149 , 465–468.     

耳唇槽舌兰——中国兰科一新种

对产于云南的兰科新种耳唇槽舌兰(Hotcoglossum auriculatum)进行了描述和绘图。该新种具有显著特征：萼片与花瓣基部有长爪;花瓣边缘具不规则齿或呈啮蚀状;唇瓣椭圆状圆形,边缘有短流苏或啮蚀状流苏,基部有爪和耳,极易区别于该属已知的种类,包括它的近缘种白唇槽舌兰(H．subulifolium)。     

管叶槽舌兰新鲜及硅胶干燥根样内生菌多样性研究

管叶槽舌兰(Holcoglossum kimballianum)是一种珍稀濒危兰科植物,其野生种群亟需保护。内生菌对兰科植物的生长发育至关重要,为评估管叶槽舌兰内生菌的多样性、分析采样方式对其内生菌的影响,该文采用高通量测序技术对迁地保育状态下新鲜与硅胶干燥的管叶槽舌兰根内生菌进行研究。结果表明:(1)新鲜及干燥管叶槽舌兰根内生菌物种组成明显不同,管叶槽舌兰内生真菌注释到6门46科51属,内生细菌注释到15门105科178属; 干燥后管叶槽舌兰根内生真菌注释到6门88科116属,内生细菌注释到21门154科336属。(2)迁地保育状态的管叶槽舌兰根样内生菌具有丰富的多样性,并且内生细菌群落丰富度和多样性远比内生真菌群落高; 经硅胶干燥后,内生真菌α多样性指数升高、β多样性指数降低,而内生细菌的α多样性指数降低、β多样性指数则升高。(3)差异显著性真菌黄盖小脆柄菇(Psathyrella candolleana)和刺盘孢属(Colletotrichum)的C. tofieldiae只存在于新鲜根样中,新鲜管叶槽舌兰差异显著性细菌是马赛菌属(Massilia),干燥根样中差异显著性细菌类群包括拜叶林克氏菌科(Beijerinckiaceae)、黄色杆菌科(Xanthobacteraceae)及慢生根瘤菌属(Bradyrhizobium)。(4)共发生网络分析显示,经干燥后管叶槽舌兰根样内生菌群落中占互作主导地位的优势物种和互作模式都发生了改变。综上认为,不同采样处理会影响管叶槽舌兰根内生菌的群落结构,在研究兰科植物根样内生菌时宜使用新鲜的根样。该研究结果为管叶槽舌兰野生种群保护及人工栽培提供了内生菌数据基础,也为兰科植物内生微生物采样方法提供了参考。