Plastome Sequences Uncover the Korean Endemic Species Polygonatum grandicaule (Asparagaceae) as Part of the P. odoratum Complex

TL;DR

This study uses plastome sequences to show that the Korean endemic Polygonatum grandicaule is part of the P. odoratum complex, despite morphological differences.

Contribution

The study provides new plastome data and proposes a taxonomic reclassification of several Polygonatum species into a single complex.

Findings

The plastomes of P. grandicaule are identical to those of P. falcatum, P. odoratum, and P. infundiflorum.

Phylogenetic analysis shows P. odoratum and its variety are nested within other species in the complex.

The study suggests using plastome-based super-barcoding for species identification in Polygonatum.

Abstract

Background/Objectives: Polygonatum grandicaule Y.S.Kim, B.U.Oh & C.G.Jang (Asparagaceae Juss.), a Korean endemic species, has been described based on its erect stem, tubular perianth shape, and pedicel length. However, its taxonomic status remains unclear due to limited molecular data. Methods: This study presents the complete plastid genomes (plastomes) of two P. grandicaule individuals and its close relative, P. odoratum (Mill.) Druce var. thunbergii (C.Morren & Decne.) H.Hara. Results: The plastomes, ranging from 154,578 to 154,579 base pairs (bp), are identical to those of P. falcatum A.Gray, P. odoratum var. odoratum, and another Korean endemic species, P. infundiflorum Y.S.Kim, B.U.Oh & C.G.Jang. All contain 78 plastid protein-coding genes (PCGs), 30 tRNA genes, and four rRNA genes, except for the pseudogene infA. Phylogenetic analyses using 78 plastid PCGs and whole intergenic spacer (IGS) regions strongly support the three sections within Polygonatum Mill. and show that P. odoratum and its variety are nested within P. falcatum, P. grandicaule, and P. infundiflorum. Conclusions: Given the limited genomic variation and phylogenetic relationships, we propose treating P. falcatum, P. grandicaule, and P. infundiflorum as part of the P. odoratum complex, despite their morphological differences. This study offers valuable putative molecular markers for species identification and supports the application of plastome-based super-barcoding in the morphologically diverse genus Polygonatum.

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