Comparative analyses on chloroplast genome between Spiraea media and Spiraea pubescens in the forest-grass transition zone of Inner Mongolia,northern China
[Objective]China is the modern distribution and differentiation center of Spiraea plants.S.media and S.pubescens are sympatric species of Spiraea distributed in the forest-grass transition zone of Inner Mongolia,northern China.Analysis of chloroplast genomic differences between the two species can provide a basis for identifying plant relatives in the same genus.[Method]In this study,the complete chloroplast genome sequences of the two species were obtained by assembly and annotation using second-generation sequencing technology and Illumina Novaseq 6000 platform,and the sequence structures were analyzed using bioinformatics methods to construct phylogenetic trees.[Result]The total length of chloroplast genome of S.media was 155 916 bp with 36.72%total GC content,and the total length of chloroplast genome of S.pubescens was 155 942 bp with 36.76%total GC content.Both were annotated to obtain 130 genes,111 of which were unique,containing 78 protein-coding genes,29 tRNA genes and 4 rRNA genes.S.media and S.pubescens detected 238 and 241 simple repeats,respectively,with codon preference ending in A or U over codon preference ending in G or C and the genomic variation regions were mainly distributed in non-coding regions.They were both with the largest number of codons encoding leucine and the least number of codons encoding cysteine.The phylogenetic tree showed that these two species formed a sister group,and had a relatively close relation.Spiraea and Sibiraea were closely related,showing a sister group relationship.[Conclusion]The results of the study can provide basic information for the phylogeny,taxonomic identification and resource development and utilization of Spiraea.