Background: Bromus inermis is a high-quality perennial forage grass in the Poaceae family, with significant ecological and economic value. While its chloroplast genome has been sequenced, the mitochondrial genome of this species remains poorly understood due to the inherent complexity and frequent recombination of plant mitochondrial genomes. Methods: We sequenced the complete mitochondrial genome of B. inermis using both Illumina Novaseq6000 and Oxford Nanopore PromethION platforms. Subsequently, comprehensive bioinformatics analyses were performed, including genome assembly and annotation, repetitive sequence identification, codon usage analysis, RNA editing site prediction, the detection of chloroplast-derived sequences, and phylogenetic reconstruction. Results: The mitochondrial genome of B. inermis was determined to be 515,056 bp in length, with a GC content of 44.34%, similar to other Poaceae species. This genome encodes 35 protein-coding genes, 22 tRNA genes, and 10 rRNA genes. Repetitive sequences account for 16.2% of the genome, totaling 83,528 bp, including 124 simple sequence repeats, 293 dispersed repeats, and 31 tandem repeats. A total of 460 RNA editing sites were identified, among which 430 were nonsynonymous. Additionally, 110 putative chloroplast-derived sequences were detected. A phylogenetic analysis based on mitochondrial genome data clarified the species’ evolutionary position within Poaceae. Conclusions: This study provides genetic resources for evolutionary research on and the communication of organelle genomes. Meanwhile, it also lays a solid foundation for the better development and utilization of the germplasm resources of B. inermis.

Thymus mongolicus (Lamiaceae) is a plant commonly found throughout China, in which it is widely used in chemical products for daily use, traditional medicinal preparations, ecological management, and cooking. In this study, we have assembled and annotated for the first time the entire mitochondrial genome (mitogenome) of T. mongolicus. The mitochondrial genome of T. mongolicus is composed in a monocyclic structure, with an overall size of 450,543 base pairs (bp) and a GC composition of 45.63%. It contains 32 unique protein-encoding genes. The repetitive sequences of the T. mongolicus mitogenome include 165 forward repetitive sequences and 200 palindromic repetitive sequences, in addition to 88 simple sequence repeats, of which tetramers accounted for the highest proportion (40.91%). An analysis of the mitogenome codons revealed that synonymous codons generally end with A/U. With the exception of nad4L, which uses ACG/ATG as an initiation codon, all other genes begin with the ATG start codon. Codon analysis of the mitogenome also showed that leucine (909) are the most abundant amino acid, while tryptophan (134) are the least prevalent. In total, 374 RNA editing sites were detected. Moreover, 180 homologous segments totaling 105,901 bp were found when the mitochondrial and chloroplast genomes of T. mongolicus were compared. Phylogenetic analysis further indicated that T. mongolicus is most closely related to Prunella vulgaris in the Lamiaceae family. Our findings offer important genetic insights for further research on this Lamiaceae species. To the best of our knowledge, this study is the first description of the entire mitogenome of T. mongolicus.

Leymus chinensis, a major component of the plant community in the eastern Eurasian grasslands with a wide distribution, provides stability to grassland ecosystems and supports animal husbandry. This study aimed to bridge the gap between the molecular breeding and industrial application of L. chinensis by conducting a comprehensive simple sequence repeat (SSR) analysis. A total of 973,129 SSRs were identified in the L. chinensis whole genome, which was used to design 20 polymorphic pairs of SSR primers to further assess 105 L. chinensis accessions. On average, 33.55 alleles were detected per locus, with an average Shannon index of 2.939 and a polymorphic information content value of 0.910. Principal coordinate, maximum likelihood, and structure analyses consistently showed that all samples were coincidentally divided into four subclasses. In addition, Mantel test data indicated a weak correlation between genetic and geographical distances in L. chinensis, whose variability may be related to the pollination mode and natural selection pressures. Finally, we used the 20 pairs of selected markers to scan 105 accessions, constructing a fingerprint for them. These findings provide new foundations for identifying superior varieties, improving the management of genetic resources, and constructing a germplasm resource database for L. chinensis.

Bromus (Poaceae Bromeae) is a forage grass with high adaptability and ecological and economic value. Here, we sequenced Bromus ciliatus, Bromus benekenii, Bromus riparius, and Bromus rubens chloroplast genomes and compared them with four previously described species. The genome sizes of Bromus species ranged from 136,934 bp (Bromus vulgaris) to 137,189 bp (Bromus ciliates, Bromus biebersteinii), with a typical quadripartite structure. The studied species had 129 genes, consisting of 83 protein-coding, 38 tRNA-coding, and 8 rRNA-coding genes. The highest GC content was found in the inverted repeat (IR) region (43.85–44.15%), followed by the large single-copy (LSC) region (36.25–36.65%) and the small single-copy (SSC) region (32.21–32.46%). There were 33 high-frequency codons, with those ending in A/U accounting for 90.91%. A total of 350 simple sequence repeats (SSRs) were identified, with single-nucleotide repeats being the most common (61.43%). A total of 228 forward and 141 palindromic repeats were identified. No reverse or complementary repeats were detected. The sequence identities of all sequences were very similar, especially with respect to the protein-coding and inverted repeat regions. Seven highly variable regions were detected, which could be used for molecular marker development. The constructed phylogenetic tree indicates that Bromus is a monophyletic taxon closely related to Triticum. This comparative analysis of the chloroplast genome of Bromus provides a scientific basis for species identification and phylogenetic studies.