Genetic diversity and population structure of pencil yam (Vigna lanceolata) (Phaseoleae, Fabaceae), a wild herbaceous legume endemic to Australia, revealed by microsatellite markers

Abstract

Pencil yam (Vigna lanceolata Benth.) (Phaseoleae, Fabaceae) is a herbaceous legume endemic to Australia. A previous morphological study suggested that pencil yam is a complex species of two or more related taxa with seven distinct morphological types (morphotypes) and, thus, taxonomic revision is necessary. In this study, we assessed genetic diversity and determined the genetic structure of a pencil yam collection of 62 accessions from seven morphotypes using 18 microsatellite (simple sequence repeat) markers with the aim to provide information for taxonomic study. In total, 138 alleles were detected with a mean of 7.67 alleles per locus. Polymorphism information content per marker varied between 0.06 and 0.90 with a mean of 0.61, while the overall gene diversity was 0.62. Bayesian clustering, principal coordinate, and neighbor-joining analyses consistently revealed that these accessions are grouped into two subpopulations with difference in number of alleles, allelic richness, and gene diversity. The population structure was not related to either morphotype or geographical origin. Gene diversity of V. lanceolata was higher than that of wild Vigna radiata (L.) Wilczek and wild Vigna umbellata (Thunb.) Ohwi & Ohashi, comparable with that of wild Vigna mungo (L.) Hepper, Vigna exilis Tateishi & Maxted, and Vigna grandiflora (Prain) Tateishi & Maxted, and lower than that of wild Vigna angularis (Willd.) Ohwi & Ohashi. These results indicated that the taxonomy of V. lanceolata should be revised and that its gene diversity was moderate compared with the other wild Vigna species.