Mycorrhizal fungi plays important roles in the seed germination and subsequent growth of orchids. The research of fungi in orchid roots, especially dominant mycorrhizal fungi is critical for orchids protection. In this study, the fungal community and composition of mycorrhizal fungi in roots, rhizomes and rhizosphere soil of Bulbophyllum tianguii grown in three terrestrial environments were analyzed by the second generation sequencing technology. The results of OTU clustering and α and β diversity analysis showed that there were significant differences in fungal communities in roots, rhizomes and rhizosphere soil of B. tianguii. The total number of OTUs in rhizomes was much less than that in roots and rhizosphere soil. The number of OTUs in rhizosphere soil and the diversity of mycorrhizal fungi were the highest. Meanwhile, the species and abundance of mycorrhizal fungi in roots and rhizomes of B. tianguii were different from those in rhizosphere soil. For different elevations, compared with B. tianguii that grow in middle of Tiankeng and top of Tiankeng, the OTUs number of B. tianguii in orchid garden is richest, and the diversity of mycorrhizal fungi in orchid garden was significantly higher than other locations. Among the three different habitats of B. tianguii, the number of OTUs in humus soil and stone habitats was notably higher than tree habitats, and the diversity of mycorrhizal fungi in humus soil was the highest. The analysis of mycorrhizal fungi in different habitats and altitudes of B. tianguii showed that Sebacina and Exophiala were the dominant mycorrhizal fungi in B. tianguii. The results of species annotation, phylogenetic tree and co-occurrence network analysis showed the dominant mycorrhizal fungi of B. tianguii mainly included Sebacina, Cladosporium, Exophiala, Fusarium. This study reveals the symbiotic relationship between Sebacina, Exophiala, Cladosporium and the B. Tianguii. It will provide a theoretical basis for the protection and biological function study of B. Tianguii.

Whether ex situ populations constructed in the limited nursery resources of botanical gardens can preserve enough genetic diversity of endangered plants in the wild remains uncertain. Here, a case study was conducted with Camellia tunghinensis, which is one of the species with the lowest natural distribution area in the sect. Chrysantha (golden camellia) of the family Theaceae. We investigated the genetic diversity and population structure of 229 samples from wild and ex situ populations using genotyping by sequencing (GBS). Core germplasm was constructed from these samples. The results showed that wild C. tunghinensis exhibited high genetic diversity, with observed heterozygosity of 0.257–0.293 and expected heterozygosity of 0.247–0.262. Compared with wild populations, the genetic diversity of ex situ populations established by transplanting wild seedlings was close to or even higher. However, the genetic diversity of those established by seed or cuttings of a few superior trees was lower. The Admixture analysis revealed that the structure of the ex situ populations derived from seeds and cuttings was relatively simple compared with the ex situ populations derived from transplanted wild seedlings and wild populations. These results suggested that direct transplanting of wild seedlings was more conducive to preserving the genetic diversity of endangered plants in the wild. In addition, wild populations demonstrated a small differentiation (mean F_ST = 0.044) among themselves, possibly due to long‐term and frequent gene flow between the wild populations. In contrast, moderate differentiation (mean F_ST > 0.05) was detected among ex situ populations and between ex situ and wild populations. This may be the combined result of the absence of gene flow pathways and strong selection pressure in various ex situ environments. Finally, 77 core germplasms were extracted from 229, likely representing the genetic diversity of C. tunghinensis. This study provides future strategies for the ex situ conservation and management of the golden camellia species and other rare and endangered plants.

Background: Understanding genetic diversity is a core issue in conservation genetics. However, previous genetic diversity evaluations of narrowly distributed species have rarely used closely related widespread species as a reference. Furthermore, identifying natural hybridization signals between narrowly and widely distributed sympatric species is of great importance for the development of species conservation programs.Methods: In this study, population genotyping by sequencing (GBS) was performed for a narrowly distributed species,Geodorum eulophioides(endemic and endangered in Southwest China), and a widespread species,G. densiflorum. A total of 18,490 high-quality single nucleotide polymorphisms (SNPs) were identified at the whole-genome level.Results: The results showed that the nucleotide diversity and heterozygosity ofG. eulophioideswere significantly higher than those ofG. densiflorum, confirming that narrowly distributed species can still preserve high genetic diversity. Consistent with taxonomic boundaries, all sampled individuals from the two species were divided into two genetic clusters and showed high genetic differentiation between species. However, in a sympatric population, a fewG. eulophioidesindividuals were detected with genetic components fromG. densiflorum, suggesting potential interspecific natural hybridization. This hypothesis was supported by Treemix analysis and hand-hybridization trials. Invasion of the habitat ofG. eulophioidesinvasion byG. densiflorumunder anthropogenic disturbance may be the main factor causing interspecific hybridization.Conclusions: Therefore, reducing or avoiding habitat disturbance is a key measure to protect theG. eulophioidespopulations. This study provides valuable information for future conservation programs for narrowly distributed species.

Cycas (family Cycadaceae), which spread throughout tropical and subtropical regions, is crucial in conservation biology. Due to subtle morphological variations between species, a solid species-level phylogeny for Cycas is lacking. In the present study, we assembled and analyzed the chloroplast genomes of six Cycas plants, including their genome structure, GC content, and nucleotide diversity. The Cycas chloroplast genome spans from 162,038 to 162,159 bp and contains 131 genes, including 86 protein-coding genes, 37 transfer RNA (tRNA) genes, and 8 ribosomal RNA (rRNA) genes. Through a comparative analysis, we found that the chloroplast genome of Cycas was highly conserved, as indicated by the contraction and expansion of the inverted repeat (IR) regions and sequence polymorphisms. In addition, several non-coding sites (psbK-psbI, petN-psbM, trnE-UUC-psbD, ndhC-trnM-CAU, and rpl32-trnP-GGG) showed significant variation. The utilization of phylogenetic analysis relying on protein-coding genes has substantiated the division of Cycas primarily into four groups. The application of these findings will prove valuable in evaluating genetic diversity and the phylogenetic connections among closely related species. Moreover, it will provide essential support for the advancement of wild germplasm resources.

Golden Camellia species are highly specific to certain soil environments. Most species are only native to calcareous soils in karst regions, except for a few that grow only in acidic soils. Our aim is to elucidate the adaptation mechanisms of the species of calcareous-soil golden Camellia (CSC) and acidic-soil golden Camellia (ASC) to habitat soils through plant–soil nutrient characteristics and their relationships. We investigated 30 indices for soils and plants. Compared with ASC, CSC had more fertile soil, while their plant tissues exhibited stronger Ca, P, and Mn and weaker K storage, which may be important mechanisms for adapting to habitat soils. However, ASC showed a higher biological absorption coefficient (BAC) for nutrients, which may contribute to the adaptation of ASC to relatively barren acidic soils. Both CSC and ASC showed much higher BAC and accumulation of Ca than other nutrients. We also found that the concentrations of nutrients in the different tissues varied considerably between species. Correlation analysis revealed 135 significant relationships between the 30 indices, with the soil pH and soil Ca levels being the most important factors influencing the nutrient uptake network. This information helps in understanding the adaptation mechanisms of karst plants to habitat soils.

The golden camellia, a highly valued ornamental plant, belongs to the Chrysantha section, the sole group in the Camellia genus that produces yellow flowers. The cultivation and broader application of this unique species have been significantly hindered by the scarcity of golden camellia and the limited knowledge of the molecular mechanisms governing yellow flower development. To investigate the dynamics of metabolite accumulation and gene expression during the yellow flower formation of C. perpetua, a continuously flowering golden camellia, a comprehensive metabolomic and transcriptomic analysis was performed across five distinct developmental stages. This analysis identified 1,160 metabolites, with flavonoids constituting the largest proportion at 21.6%. Comparative transcriptomic profiling indicated that differentially expressed genes (DEGs) associated with photosynthesis were predominantly active during the early stages of flower development, while DEGs involved in the flavonoid biosynthesis pathway showed a marked increase as the flowers matured. The integrated metabolomic and transcriptomic data highlighted the pivotal regulatory role of the flavonoid biosynthesis pathway in the formation of yellow flowers in C. perpetua, identifying 50 key genes and 17 crucial metabolites and mapping their interaction networks. Furthermore, weighted gene co-expression network analysis pinpointed several hub genes, such as flavonol synthase, which are likely critical to flavonoid production due to their elevated expression levels, particularly in the early bud and yellowing phases. This study provides valuable insights into the molecular pathways that underlie yellow flower development in golden camellia species.