ISSN 1346-7565 Acta Phytotax. Geobot. 71 (3): 187–199 (2020) doi: 10.18942/apg.202003 A Revised Infrageneric Classification of Old World Species of Dioscorea (Dioscoreaceae) 1,* 1 2 3 3 HIROSHI NODA , SHIZUKA FUSE , JUN YAMASHITA , RACHUN POOMA , MANOP POOPATH , 1 1 HIROSHI TOBE AND MINORU N. TAMURA 1Department of Botany, Graduate School of Science, Kyoto University, Kitashirakawa-oiwake-cho, Sakyo-ku, Kyoto 606-8502, Japan. *
[email protected] (author for correspondence); 2Institute of Plant Science and Resources, Okayama University, Chuo 2-20-1, Kurashiki-shi, Okayama 710-0046, Japan; 3The Forest Herbarium, Department of National Parks, Wildlife and Plant Conservation, Chatuchak, Bangkok 10900, Thailand Dioscorea (Dioscoreaceae), a morphologically diverse genus, consists of more than 600 species distrib- uted worldwide. Recent molecular and morphological analyses allowed us to recognize two subgenera, Dioscorea and Helmia, and 19 Old World species groups (sections) in subgenus Helmia. In this paper we present a diagnostic key and taxonomic treatment for the subgenera and sections, including D. sect. Ta- mus (stat. nov.) and four new sections; Afroborderea, Perennia (validated here), Pseudoshannicorea and Pseudostenophora. Lectotype species for eleven sections; Enantiophyllum, Illigerastrum, Lasiophyton, Macrocarpaea, Macropoda, Madagascarienses, Orientali-asiaticae, Rhacodophyllum, Shannicorea, Stenophora and Syntepaleia, are also designated. Keywords: Dioscorea, Dioscorea sect. Afroborderea, Dioscorea sect. Perennia, Dioscorea sect. Pseu- doshannicorea, Dioscorea sect. Pseudostenophora, Dioscorea sect. Tamus, Dioscorea subg. Helmia, Dioscoreaceae, lectotypification, taxonomy Dioscorea (Dioscoreaceae), yams, are mostly used by combining all existing cpDNA sequence dioecious vines with twining stems (Fig. 1). data obtained in previous studies (Caddick et al. Based on their great morphological diversity, 2002a, Wilkin et al.