Plastome evidence for the reclassification of Scorzonera gageoides within Gelasia (Asteraceae)

The complete chloroplast (cp) genomes of Scorzonera gageoides and Gelasia circumflexa were sequenced, assembled, and analyzed to clarify the systematic position of S. gageoides . Both cp genomes exhibited the typical quadripartite structure of angiosperms, comprising a large single-copy (LSC) region, a small single-copy (SSC) region, and two inverted repeats (IRs). The genome sizes were 152,892 bp for S. gageoides and 152,917 bp for G. circumflexa , with identical overall GC contents of 37.6%. Both genomes encoded 113 unique genes, including 80 protein-coding genes, 29 tRNAs, and 4 rRNAs. Eighteen genes were duplicated within the IRs, and 17 genes contained introns. Phylogenetic analyses based on cp sequences (156,866 bp) and ITS sequences (557 bp) consistently placed S. gageoides as sister to G. circumflexa , with near-identical cp genomes (genetic distance 0.001) and strong bootstrap support. Morphologically, the two species share a tuberous-rooted habit, coriaceous pubescent leaves, homogamous capitula, and lanate achenes, differing mainly in leaf width, venation, and margin morphology. Combined molecular and morphological evidence supports transferring S. gageoides to Gelasia as Gelasia gageoides (Boiss.) Karimov, Yuldashev, Yusupov, Kim & Tojibaev, comb. nov. This study provides genomic resources for further phylogenetic and conservation studies in Asteraceae.

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