Comparative Chloroplast Genomics and Phylogenetic Relationships of Poa angustifolia and Poa lipskyi (Poaceae)

Abstract

Poa L. (Poaceae), comprising over 500 species, is taxonomically challenging due to morphological plasticity, hybridization, and polyploidy. To clarify plastome architecture and phylogenetic relationships within the genus, we sequenced and annotated complete chloroplast genomes of Poa angustifolia (accessions P10, P14) and Poa lipskyi (P17) from Uzbekistan. The three plastomes (135,310–135,609 bp) shared the typical quadripartite structure and an identical complement of 130 genes across self-replication, photosynthesis, and other functional categories. Codon usage and amino acid composition were highly conserved, with a consistent bias toward A/T-ending codons and leucine, isoleucine, glycine, and serine as the dominant residues. Sliding-window analysis identified two nucleotide-diversity hotspots, in the rpl32 – trnL -UAG and trnC -GCA– rpoB regions, and SSR profiling showed predominant mononucleotide A/T repeats alongside a few taxon-specific pentanucleotide motifs. Maximum-likelihood phylogenomic analysis placed the P. angustifolia accessions in a strongly supported clade sister to P. lipskyi , consistent with shared membership in sect. Poa. These results indicate that Poa plastomes are structurally conserved yet retain informative variable regions useful for phylogenetics and barcoding.