The Complete Chloroplast Genome of Poa pratensis (Poaceae), a High-Quality Forage

Poa pratensis L. (Poaceae) is a hardy, persistent, attractive forage and turf grass adapted to a wide range of soils and climate. In this study, we release and detail the complete chloroplast genome sequences of P. pratensis. The whole chloroplast genome was 135,649 bp in length and comprised 131 genes, including 85 protein-coding genes, 38 tRNA genes, 8 rRNA genes. The P. pratensis chloroplast genome had a GC content of 38.3%. The result of phylogenetic analysis showed that P. pratensis was closely related to P. pratensis cv. Qinghai and P. poophagorum. This study would provide useful genetic information for the protection of P. pratensis and other related species.


Introduction
Poa pratensis L., also known as Kentucky bluegrass, belongs to the Poaceae family. It is a hardy, persistent, attractive forage and turf grass adapted to a wide range of soils and climate [1]. P. pratensis is widely used in lawns, golf courses, landscapes, and sports fields as a prominent cool-season grass [2], and is the longest-established non-native vascular plant in the Antarctic [3]. The chloroplast genome can provide valuable genomic information for the systematic study and the conservation of rare species [4] [5]. Here, we sequenced and analyzed the complete chloroplast genome genome of P. pratensis based on Next-generation sequencing technology and compared it with other genome sequences of Trib. Poeae (Poaceae).

Materials and Methods
The samples of P. pratensis were collected in Ledu County, China (102.3E, 36.4N) and the voucher specimens (JingML2019002) are deposited in the Herbarium of College of Pharmacy, Qinghai Nationalities University, Xining, China. The whole-genome sequencing was conducted by Nanjing Genepioneer Biotechnologies Inc. (Nanjing, China) with the Illumina NovaSeq Sequencing System. Approximately 6.12 GB of clean data were yielded. The high-quality reads were applied to a de novo assembly performed using the program SPAdes assembler v3.10.1 [6]. The trimmed reads were mainly annotated by CpGAVAS2 (http://47.96.249.172:16019/analyzer/home; [7]).

Discussion
In order to reveal the phylogenetic position of P. pratensis with its close allies, a phylogenetic analysis was performed based on twelve complete chloroplast genomes sequence of of Trib. Poeae (Poaceae). The sequences were aligned by MAFFT v7.307 [8] and the maximum-likelihood tree (Figure 2) was built using MEGA7 [9]. Using the Tamura-Nei model model the ML phylogenetic analysis were conducted with MEGA v7.0.26 generating 200 bootstrap replicates to determine measures of nodal support with each run initiating from a random starting tree.

Conclusions
According to the result of phylogenetic analysis (Figure 1), the phylogenetic tree showed that P. pratensis was closely related to P. pratensis cv. Qinghai and P. poophagorum. P. pratensis cv. Qinghai is a common cultivated variety of P. pratensis, and its chloroplast genome has been reported by Wei et al. [10]. The P. pratensis cv. Qinghai chloroplast genome reported in paper of Wei et al. [10] is 43 bp shorter, and 6 fewer genes than the chloroplast genome we obtained. Such genomic differences may be the result of artificial domestication. This study would provide useful genetic information for the protection of P. pratensis and other related species.

Data Availability
The genome sequence data that support the findings of this study are openly available in GenBank of NCBI at https://www.ncbi.nlm.nih.gov/ under the accession number MT295102. The associated BioProject, SRA, and Bio-Sample numbers are PRJNA699977, SRR13647703, and SAMN17817424 respectively.

Conflicts of Interest
No potential conflict of interest was reported by the authors.