The taxonomic status of the wild rice species Oryza ridleyi Hook. f. and O . longiglumis Jansen (Ser. Ridleyanae Sharma et Shastry) from Southeast Asia

The taxonomic status of the two species O . ridleyi and O . longiglumis in Oryza series Ridleyanae was resolved using morphological and molecular markers. Cluster analysis using a similarity matrix based on 12 qualitative characters separated the O . ridleyi from the O . longiglumis samples and the O . ridleyi samples from Papua New Guinea (PNG). O . ridleyi and O . longiglumis formed distinct groups upon cluster analysis based on 16 quantitative characters. Canonical discriminant analysis showed significant differences between the two species with anther and ligule length and spikelet and leaf dimensions as the most discriminating characters. Cluster analysis based on RAPD markers showed distinct clusters for O . longiglumis and O . ridleyi samples from different geographic origins. Hybridization studies revealed an F 1 sterility barrier in interspecific hybrids and those obtained from intraspecific crosses between O . ridleyi from Southeast Asia and PNG.