The Complete Chloroplast Genome and the Phylogenetic Analysis of Panicum bisulcatum (Thumb.) (Poaceae)

The chloroplast (cp) genome of <i>Panicum bisulcatum</i> (Thumb.), a significant agricultural weed, was sequenced and characterized to elucidate its genomic architecture, evolutionary dynamics, and phylogenetic relationships. The complete cp genome was assembled as a circular DNA molecule of 138,489 bp, exhibiting a typical quadripartite structure comprising a large single-copy (LSC, 82,260 bp), a small single-copy (SSC, 12,569 bp), and a pair of inverted repeats (IR, 21,830 bp each) regions. It encodes 135 genes, including 89 protein-coding genes, 49 tRNAs, and 8 rRNAs. Functional annotation revealed that most genes are involved in photosynthesis and genetic system. A total of 51 simple sequence repeats (SSRs) and 62 long repeats (LRs) were identified, providing potential molecular markers. Comparative analysis of IR boundaries highlighted both conserved features and species-specific expansion/contraction events among <i>Panicum</i> species. Phylogenomic analysis robustly placed <i>P. bisulcatum</i> within the genus <i>Panicum</i>, showing a closest relationship with <i>P. incomtum</i> and confirming the monophyly of the genus. Furthermore, single nucleotide polymorphism (SNP) analysis with its closest relative, <i>P. incomtum</i>, revealed 4659 SNPs, with a dominance of synonymous substitutions, indicating the action of purifying selection. This study provides the first comprehensive cp genomic resource for <i>P. bisulcatum</i>, which will facilitate future studies in species identification, phylogenetic reconstruction, population genetics, and the development of sustainable management strategies for this weed.