Background: Section Camellia is the most diverse group in the genus Camellia L., and this group of plants has a long history of cultivation in China as popular ornamental flowers and oil plants. Sect. Camellia plants present diverse morphological variations and complexity among species, resulting in uncertainty in the classification of species, which has resulted in a degree of inconvenience and confusion in the use of plant resources and research. Methods: Here, We sequenced and assembled the chloroplast genomes of 6 sect. Camellia and performed comparative chloroplast genome analysis and phylogenetic studies combined with 15 existing sect. Camellia plants. Results: The chloroplast genome of 21 species in sect. Camellia species were quadripartite with length of 156,587–157,068 bp base pairs (bp), and a highly conserved and moderately differentiated chloroplast genome arrangement. The 21 sect. Camellia chloroplast genomes were similar to those of angiosperms, with high consistency in gene number, gene content and gene structure. After the annotation process, we identified a total of 132 genes, specifically 87 sequences coding for proteins (CDS), 37 transfer RNA (tRNA) genes, and 8 ribosomal RNA (rRNA) genes. The ycf1 gene in 21 species of the sect. Camellia was present only in the small single-copy/inverted repeat of a (SSC/IRa) region. Sequence variation was greater in the large single-copy (LSC) region than in the IR region, and the majority of the protein-coding genes presented high codon preferences. The chloroplast genomes of 21 plant species exhibit relatively conserved SC (single copy region)/IR (inverted repeat region) boundaries. We detected a total of 2975 single sequence repeats (SSRs) as well as 833 dispersed nuclear elements (INEs). Among these SSRs, A/T repeats and AT/AT repeats dominated, while among INEs, forward repeats and palindromic repeats predominated. Codon usage frequencies were largely similar, with 30 high-frequency codons detected. Comparative analysis revealed five hotspot regions (rps16, psaJ, rpl33, rps8, and rpl16) and two gene intervals (atpH-atpI and petD-rpoA) in the cp genome, which can be used as potential molecular markers. In addition, the phylogenetic tree constructed from the chloroplast genome revealed that these 21 species and Camellia oleifera aggregated into a single branch, which was further subdivided into two evolutionarily independent sub-branches. Conclusions: It was confirmed that sect. Camellia and C. oleifera Abel are closely related in Camellia genus. These findings will enhance our knowledge of the sect. Camellia of plants, deepen our understanding of their genetic characteristics and phylogenetic pathways, and provide strong support for the scientific development and rational utilization of the plant resources of the sect. Camellia.

Sect. Tuberculata, as one of the endemic plant groups in China, belongs to the genus Camellia of the Theaceae family and possesses significant economic and ecological value. Nevertheless, the characteristics of habitat distribution and the major eco-environmental variables affecting its suitability are poorly understood. In this study, using 65 occurrence records, along with 60 environmental factors, historical, present and future suitable habitats were estimated using MaxEnt modeling, and the important environmental variables affecting the geographical distribution of sect. Tuberculata were analyzed. The results indicate that the size of the its potential habitat area in the current climate was 1.05 × 10⁵ km², and the highly suitable habitats were located in Guizhou, central-southern Sichuan, the Wuling Mountains in Chongqing, the Panjiang Basin, and southwestern Hunan. The highest probability of presence for it occurs at mean diurnal range (bio2) ≤ 7.83 °C, basic saturation (s_bs) ≤ 53.36%, temperature annual range (bio7) ≤ 27.49 °C, −7.75 °C < mean temperature of driest quarter (bio9) < 7.75 °C, annual UV-B seasonality (uvb2) ≤ 1.31 × 10⁵ W/m², and mean UV-B of highest month (uvb3) ≤ 5089.61 W/m². In particular, bio2 is its most important environmental factor. During the historical period, the potential habitat area for sect. Tuberculata was severely fragmented; in contrast, the current period has a more concentrated habitat area. In the three future periods, the potential habitat area will change by varying degrees, depending on the aggressiveness of emissions reductions, and the increase in the potential habitat area was the largest in the SSP2.6 (Low-concentration greenhouse gas emissions) scenario. Although the SSP8.5 (High-concentration greenhouse gas emissions) scenario indicated an expansion in its habitat in the short term, its growth and development would be adversely affected in the long term. In the centroid analysis, the centroid of its potential habitat will shift from lower to higher latitudes in the northwest direction. The findings of our study will aid efforts to uncover its originsand geographic differentiation, conservation of unique germplasms, and forestry development and utilization.

Background/Objectives: Species within section Chrysantha represent the only camellias known to produce golden-yellow petals. The primary objectives of this study were to characterize the chloroplast genome structure of Camellia tianeensis and to elucidate its phylogenetic position with sect. Chrysantha. Methods: The complete chloroplast genome of C. tianeensis was sequenced, assembled, and annotated. Phylogenetic inference was conducted using maximum likelihood and Bayesian methods based on complete chloroplast genomic sequences. Results: The chloroplast genome of C. tianeensis is 156,865 bp in length and exhibits a typical quadripartite structure consisting of a large single-copy (LSC) region (86,579 bp), a small single-copy (SSC) region (18,236 bp), and two inverted repeat (IR) regions (26,025 bp each). The genome encodes 164 genes, including 111 protein-coding genes, 45 tRNAs, and 8 rRNA genes. The overall GC content was 37.32%, with regional values of 35.33% (LSC), 30.59% (SSC), and 42.99% (IRs). Sixty-nine simple sequence repeats (SSRs) were identified, predominantly mononucleotide repeats, Thirty-eight dispersed repeats were categorized into three types (forward, reverse, and palindromic), with no complement repeats detected. Phylogenetic analysis strongly supported that C. tianeensis is a member within sect. Chrysantha. Conclusions: C. tianeensis is phylogenetically closely related to C. huana, forming a well-supported clade. This study enhances the molecular research available for sect. Chrysantha and provides a genomic foundation for future phylogenetic and taxonomic studies in this group.

Sect. Tuberculata as one of the endemic plant groups in China, it belonging to the genus Camellia of the Theaceae family, possessing significant economic and ecological value. Nevertheless, the characteristics of habitat distribution and the major eco-environmental variables affecting its suitability are poorly understood. In this study, we have using 65 occurrence records along with 60 environmental factors, historical, present and future suitable habitats were estimated using MaxEnt modeling, and the important environmental variables affecting its geographical distribution were analyzed. The results indicate that the size of the potential habitat area of it in the current climate was 1.05 × 105 km2, and the highly suitable habitats were located in Guizhou, central-southern Sichuan, the Wuling Mountains in Chongqing, the Panjiang Basin, and southwestern Hunan. The highest probability of presence for it occurs at bio2 ≤ 7.83 °C, S_bs ≤ 53.36%, bio7 ≤ 27.49 °C, -7.75 °C < bio9 < 7.75 °C, uvb2 ≤ 1.31 × 105 W/m2, and uvb3 ≤ 5089.61 W/m2. In particular, bio2 is the most important environmental factor for it. During thehistorical, the potential habitat area of it was severely fragmented; in contrast, it is much more contiguous in the current period. In the three future periods, the potential habitat area will change by varying degrees, depending on the aggressiveness of emissions reductions, and the increase in the potential habitat area was the largest in the RCP2.6 scenario. Although the RCP8.5 scenario indicated an expansion in the habitat of it in the short term, their growth and development would be adversely affected in the long term. In the centroid analysis, the centroid of the potential habitat of it will shift from lower to higher latitudes in the northwest direction. The findings of our study will aid efforts to uncover the origins of it, their geographic differentiations, conservation of unique germplasms, and forestry development and utilization.

Idesia polycarpa Maxim (Salicaceae) is an endemic woody oil tree native to China with multi-purpose economic and ecological applications, including seed oil production, timber utilization, landscape afforestation and biomass exploitation. To date, a unified phenological classification system tailored to this species remains unavailable, restricting standardized cultivation practices and germplasm phenotypic assessment. Here, we developed the first comprehensive Biologische Bundesanstalt, Bundessortenamt und CHemische Industrie (BBCH) scale phenological coding system for I. polycarpa through two consecutive full-year phenological monitoring trials in Guizhou Province, Southwest China. We defined eight principal growth stages spanning the complete annual cycle: bud development, leaf expansion, shoot elongation, inflorescence differentiation, blooming, fruit development, fruit ripening, and leaf senescence coupled with dormancy initiation, together with 40 morphologically described secondary stages supported by field photographic documentation. Synchronous vegetative and reproductive growth was observed, while staminate individuals exhibited earlier and longer flowering periods relative to pistillate trees. Three female genotypes were harvested at BBCH principal stage 89 (full fruit maturity) to verify the applicability of the established scale. Distinct genotypic differences in fruit dimensional traits, 1000-seed weight and fatty acid composition were characterized, confirming that BBCH-standardized harvesting eliminates confounding temporal biases for oil quality comparisons. This standardized BBCH coding system offers a universal phenological descriptor for I. polycarpa and delivers actionable protocols for orchard fertilization, canopy pruning, pollinizer arrangement and uniform fruit collection. Our findings establish a baseline phenotypic framework to facilitate germplasm discrimination, targeted breeding and intensive sustainable production of this commercially valuable indigenous oil tree.

Section Chrysantha plants are the only camellias with golden yellow flower petals. In this study, the complete genome of the chloroplast of Camellia tianeensis was determined. The results showed that the complete chloroplast genome of C. tianeensis was 156,865 bp in length; had a typical tetrameric structure; and had a large copy region (LSC), a small copy region (SSC), and two inverted repetitive regions (IRs) with lengths of 86,579 bp, 18,236 bp, and 26,025 bp, respectively. A total of 164 genes were identified, containing 111 protein-coding genes, 45 tRNAs, and 8 rRNA genes; the total GC content was 37.32%, including 35.33% of the LSC, 30.59% of the SSC, and 42.99% of the IRs. There were 69 simple sequence repeats (SSRs) in C. tianeensis, with the number of single nucleic acid repeats being significantly greater than the number of other repeat types. There were 38 dispersed repeats categorized into three types, and no complement (C) repeats were found; The phylogenetic tree supports that C. tianeensis is a constituent member of sect. Chrysantha. Therefore, the results not only enrich the sect. Chrysantha molecular database, but also provide a framework for future studies on the evolution and taxonomic revision of the sect. Chrysantha.