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Hibiscus mutabilis is native to China with a long cultivation history, and is an ancient garden tree species and medicinal plant. In this study, we selected three cultivars of H. mutabilis in a hybrid combination(H. mutabilis cv. Danbanbai, H. mutabilis cv. Jinqiusong, H. mutabilis cv. Mudanfen)to investigate evolutionary characteristics between the cultivars of H. mutabilis and its related species, and clarify the phylogenetic relationship between the cultivars of H. mutabilis and its related species, as well as explore the genetic model of chloroplast genome(cpDNA)of H. mutaibilis at the same time. We first sequenced the three cultivars of H. mutaibilis using Illumina NovaSeq. After assembly and annotation, three complete chloroplast genome sequences were obtained. The cpDNAs of the related species H. taiwanensis from our group, and H. syricus and H. rosa-sinensis from the gene bank. Then we carried out comparative analysis on composition and structure of cpDNAs of four species of Hibiscus and three cultivars of H. mutabilis, and completed its phylogenetic tree reconstruction. The results were as follows: (1)Total sizes of cpDNAs of H. mutabilis cv. Danbanbai, H. mutabilis cv. Jinqiusong, H. mutabilis cv. Mudanfen were 160 880, 160 879, 160 920 bp, respectively, and the total gene number was 130, including 85 protein-coding genes, eight ribosomal RNAs, and 37 transfer RNAs. (2) The comparative analyses showed that the cpDNAs of three cultivars of H. mutabilis and the related species H. taiwanensis were highly conserved, and the inverted repeat regions(IR)were all 26 300 bp; H. rosa-sinensis and H. syriacus shrank to at 25 745 and 25 598 bp, respectively.(3)The phylogenetic analysis revealed that the three cultivars were planted into a monophyletic branch, and then together with H. taiwanensis into a high support branch, indicating that H. mutabilis and H. taiwanensis had the closest relationship; Compared with H. syriacus and H. rosa-sinensis, H. mutabilis and H. taiwanensis were more closely related to H. hamabo, H. tiliaceum and H. canabinus.(4)Three cultivars of H. mutabilis could be distinguished by cpDNA sequence, the length of LSC/SSC of H. mutabilis cv. Danbanbai, H. mutabilis cv. Jinqiusong, H. mutabilis cv. Mudanfen were 89 355 bp/18 925 bp, 89 353 bp/18 926 bp, 89 400 bp/18 920 bp, respectively. And candidate molecular markers and DNA barcodes had been developed from repeat sequence and nucleotide diversity analyses, which could be used as a tool for cultivars identification.(5)The cpDNAs of H. mutabilis cv. Danbanbai and H. mutabilis cv. Jinqiusong showed a minimum difference and had the closest phylogenetic relationship. According to the relationship between their female and offspring, the maternal genetic characteristics of the cpDNAs of Hibiscus were proved. This study will help us to understand the evolutionary characteristics and phylogenetic relationship of cpDNAs of three cultivars of H. mutabilis and H. taiwanensis, and provide basic data on cpDNA for accurate identification of the cultivars of H. mutabilis and breeding of excellent cultivars. [ABSTRACT FROM AUTHOR]

Carpinus tientaiensis is an endangered plant species with sparse population densities and is endemic to China. The distribution of this species is restricted to the territory of Zhejiang Province and its survival rate is very low. Based on data of chloroplast genome(cpDNA)single nucleotide polymorphism(SNP)in six natural populations(including the mother plants of all populations), we investigated genealogical structure and systematic development, assessed how endangered C. tientaiensis is and put forward relevant conservation strategies. The genomic DNA of C. tientaiensis was extracted using TIANGEN kit method and a library was constructed for high-throughput sequencing with Illumina NovaSeq 6000. To obtain the sequence of chloroplast complete genome, cpDNA maps were constructed using the online program OGDRAW. Nucleotide diversity was analyzed by DnaSP software while PopART was used for haploid network construction and RAxML was adopted for maximum likelihood(ML)tree construction. Finally, MrBayes software was used for construction of Bayes tree. The results were as follows:(1)According to chloroplast complete genome sequence analysis of C. tientaiensis, most of the protein-coding genes and amino acid sequences showed obvious codon preference. Moreover, chloroplast long-term relationship(cpLTR)revealed 32 forward repeats, 25 palindromic repeats and 22 reverse repeats. We detected 87 simple sequence repeats(SSR)in different types, most of which were A/T rich and the number of single nucleotides was the largest.(2)A total of 314 SNPs was identified in the cpDNA of C. tientaiensis. Single-nucleotide substitution indicated that C. tientaiensis was monophyletic and could be categorized into Tiantai County(THS)and Jingning County(JST)populations. The evolution of the haplotypes of the population manifested stellar radiation.(3)The variation of nucleotide diversity was low in all populations(Pi<0.005)and the haplotype diversity of THS and JST populations was also low(Hd 0.5-0.6). This indicated that C. tientaiensis had undergone historically local expansions after experiencing bottlenecks across its evolution history, with lower genetic variation within populations and higher level of diversity among populations. The results of SNP of the cpDNA reveal the genetic diversity and lineage differentiation of C. tientaiensis, and provide theoretical basis for conservation of the genetic resources as well as rescue of this endangered plant species. [ABSTRACT FROM AUTHOR]