THE COMPLETE CHLOROPLAST GENOME OF A MEDICINAL PLANT, Inula grandis (Asteraceae)

Abstract

The genus Inula (Asteraceae) includes numerous medicinally important species, but phylogenetic relationships within the Inula complex remain difficult to resolve using morphological characters alone. In this study, we assembled and annotated the complete chloroplast genome of Inula grandis using Illumina paired-end sequencing data and compared it with 24 publicly available plastome accessions representing 13 additional species of Inula, Carpesium, Pentanema, and Limbarda. The chloroplast genome of I. grandis was 151,160 bp in length and exhibited the typical quadripartite structure consisting of a large single-copy region, a small single-copy region, and two inverted-repeat regions. Comparative analysis showed that the LSC/IR and IR/LSC boundaries were generally conserved, whereas greater variation was detected at the IRb/SSC junction. Sliding-window analysis identified several highly variable regions that may provide candidate markers for future phylogenetic and DNA-barcoding studies; however, their discriminatory power requires validation using broader taxon and population sampling. Maximum-likelihood analysis placed I. grandis with several Carpesium accessions, whereas most sampled Inula accessions were recovered in a separate lineage together with Pentanema britannicum and two accessions identified as Carpesium abrotanoides. These findings reveal discordance between plastome relationships and currently recognized generic boundaries within the Inula complex. Because the present analysis is based exclusively on chloroplast genomes and includes limited taxon sampling, no formal taxonomic changes are proposed. Broader sampling based on verified voucher specimens and the integration of nuclear genomic and morphological data are required to clarify evolutionary relationships within the group.