Background: Studying population genetic structure and gene flow of plant populations and their influencing factors is of particular significance in the field of conservation biology, especially important for species such as rare and endangered plants. Tetraena mongolica Maxim. (TM), belongs to Zygophyllaceae family, a rare and endangered plant with narrow distribution. However, for the last decade, due to excessive logging, urban expansion, industrial and tourism development, habitat fragmentation and loss of natural habitats have become major threats to the population of endangered plants. Results: In this study, genetic diversity, population genetic structure and gene flow of TM populations were evaluated by reduced representation sequencing technology, and a total of more than 133.45 GB high-quality clean reads and 38,097 high-quality SNPs were generated. Analysis based on multiple methods, we found that the existing TM populations have moderate levels of genetic diversity, and very low genetic differentiation as well as high levels of gene flow between populations. Population structure and principal coordinates analysis showed that 8 TM populations can be divided into two groups. The Mantel test detected no significant correlation between geographical distances and genetic distance for the whole sampling. Moreover, the migration model indicated that the gene flow is more of a north to south migration pattern in history. Conclusions: This study demonstrates that the present genetic structure is mainly due to habitat fragmentation caused by urban sprawl, industrial development and coal mining. Our recommendation with respect to conservation management is that, all 8 populations should be preserved as a whole population, rather than just those in the core area of TM nature reserve. In particular, the populations near the edge of TM distribution in cities and industrial areas deserve our special protection.

Background: Genetic diversity, genetic structure, and gene flow in plant populations and their influencing factors are important in conservation biology. Cypripedium macranthos is one of the few wild orchids with high ornamental value in northern China. However, over the past decade, excessive collection, trading, tourism development, habitat fragmentation, deceptive pollination, and seed germination difficulties have all caused a sharp decline in the number of C. macranthos individuals and its population. In order to propose a scientific and effective conservation strategy, the genetic diversity, genetic structure and gene flow of the current CM population are urgent scientific issues to be clarified. Results: Here, 99 individuals of C. macranthos from north and northeast China were analyzed to evaluate the genetic diversity, gene flow among populations, and genetic structure by genotyping-by-sequencing. More than 68.44 Gb high-quality clean reads and 41,154 SNPs were obtained. Our data based on bioinformatics methods revealed that C. macranthos has lower genetic diversity, high levels of historical gene flow, and moderate-to-high genetic differentiation between populations. The gene migration model revealed that the direction of gene flow was mainly from northeast populations to north populations in China. The results of genetic structure analysis showed that 11 C. macranthos populations can be considered as two groups, and further divided into four subgroups. Moreover, the Mantel test detected no significant “Isolation by Distance” between populations. Conclusions: Our study demonstrates that the present genetic diversity and genetic structure of C. macranthos populations were mainly caused by biological characteristics, human interference, habitat fragmentation, and restricted gene flow. Finally, constructive measures, which can provide a basis for the proposal of conservation strategies, have been suggested.

Lindera glauca(Lauraceae) is a tree of economic and ecological significance that reproduces sexually and asexually via apomictic seeds. It is widely distributed in the low-altitude montane forests of East Asia. Despite the potential implications of a mixed reproductive system in terms of genetic diversity, few studies have focused on this aspect. In this study, the genetic structure of wild populations ofL. glaucawas investigated via genetic analyses. Overall, 13 nuclear microsatellites (nSSRs) and five chloroplast microsatellites (cpSSRs) were used to genotype 300 individual plants, taken from 20 wild populations (a small sample size in some wild populations is due to the limitation of its specific reproduction, leading to certain limitations in the results of this study) and two cultivated populations ranging across nearly the entire natural distribution of mainland China. The populations exhibited low levels of genetic diversity (nSSR:A_R= 1.75,Ho= 0.32,He= 0.36; cpSSR:Nb= 2.01,Hrs= 0.40), and no significant effect of isolation by distance between populations existed, regardless of marker type (nSSR:R²= 0.0401,P= 0.068; cpSSR:R²= 0.033,P= 0.091). Haplotype networks showed complex relationships among populations, and the H12 haplotype was predominant in most populations. Analyses of molecular variance obtained with nuclear markers (Fsc = 0.293,F_ST= 0.362) and chloroplast markers (Fsc = 0.299,F_ST= 0.312) were similar. The migration ratio of pollen flow versus seed flow in this study was negative (r= −1.149). Results suggest that weak barriers of dispersal between populations and/or the similarity of founders shared between neighbors and distant populations are indicative of the gene flow between populations more likely involving seeds. WildL. glaucain mainland China was inferred to have highly skewed sex ratios with predominant females. In addition, some populations experienced a recent bottleneck effect, especially in Gujianshan, Chongqing, and southwest China (population GJS). It is suggested that few wild male individuals should be conserved in order to maintain overall genetic diversity in the wild populations of this species. These findings provide important information for the sustainable utilization and preservation of the overall genetic diversity ofL. glauca.

Lindera glauca is a crucial source of diverse industrial oil and medicines. The spicy aroma of tender leaves is caused by the presence of abundant aromatic compounds. Here, we present its chromosome-level genome assembly comprising 12 pseudochromosomes (2,092.2 Mb; scaffold N50: 186.5 Mb), which was predicted to have 65,145 protein-coding genes. Comparative genomic analyses indicated two whole-genome duplication (WGD) events in the Lauraceae family, contributing to the production of numerous terpene synthase (TPS) genes. We identified 138 TPS genes in L. glauca. Comparative transcriptomic analyses revealed high expression of genes Lg03G2346 and Lg08G140 in TPS-a and Lg07G2961 and Lg12G971 in TPS-b subfamilies, which regulated the biosynthesis of the monoterpenoid β-ocimene and sesquiterpenoid D-germacrene in L. glauca. The results suggested a molecular basis for species-specific terpenoid biosynthesis and provided a foundation for molecular breeding to produce desired characteristics and a valuable reference genome.

Schoenoplectus tabernaemontani (C. C. Gmelin) Palla is a typical macrophyte in diverse wetland ecosystems. This species holds great potential in decontamination applications and carbon sequestration. Previous studies have shown that this species may have experienced recent polyploidization. This would make S. tabernaemontani a unique model to study the processes and consequences of whole-genome duplications in the context of the well-documented holocentric chromosomes and dysploidy events in Cyperaceae. However, the inference was not completely solid because it lacked homology information that is essential to ascertain polyploidy. We present here the first chromosome-level genome assembly for S. tabernaemontani. By combining Oxford Nanopore Technologies (ONT) long reads and Illumina short reads, plus chromatin conformation via the Hi-C method, we assembled a genome spanning 507.96 Mb, with 99.43% of Hi-C data accurately mapped to the assembly. The assembly contig N50 value was 3.62 Mb. The overall BUSCO score was 94.40%. About 68.94% of the genome was comprised of repetitive elements. A total of 36,994 protein-coding genes were predicted and annotated. Long terminal repeat retrotransposons accounted for ∼26.99% of the genome, surpassing the content observed in most sequenced Cyperid genomes. Our well-supported haploid assembly comprised 21 pseudochromosomes, each harboring putative holocentric centromeres. Our findings corroborated a karyotype of 2n = 2X = 42. We also confirmed a recent whole-genome duplication occurring after the divergence between Schoenoplecteae and Bolboschoeneae. Our genome assembly expands the scope of sequenced genomes within the Cyperaceae family, encompassing the fifth genus. It also provides research resources on Cyperid evolution and wetland conservation.