Camellia oleifera, belonging to the genus Camellia, is an important woody edible oil plant with high ecological and economic values. In this study, we assembled a chromosome-level genome of Camellia brevistyla that represents the closest diploid relative of polyploid C. oleifera based on current research. The genome size of the assembly was 3.10 Gb with a contig N50 size of 88.60 Mb. The BUSCO completeness score was estimated to be 98.88%, indicating high assembly completeness. A total of 2.29 Gb of the sequences were annotated as repetitive elements, accounting for 73.67% of the entire genome assembly. A total of 35,093 protein-coding genes were predicted, with the annotation completeness evaluated to be 97.03% via BUSCO analysis. In conclusion, the high-quality C. brevistyla genome is a pivotal genetic resource within the genus Camellia, which can serve as a vital diploid comparator for evolutionary and genomic studies in the more complex polyploid C. oleifera.

Chinquapin (Castanea henryi) is an important nut-producing tree species in southern China. Symbiosis with ectomycorrhizal fungi (EF) can promote nutrient absorption, which is correlated with colonization rate (CR). Lateral roots (LR) development is a precursor of ectomycorrhizal formation, and exogenous indole-3-butyric acid (IBA) is known to promote LR development. However, it is still not known whether IBA application increases ectomycorrhizal CR and improves nutrient absorption. Also, how do host plants respond to exogenous IBA at the physiological and gene levels is still not clear. To eliminate the influence of fungal growth rate on symbiosis, we selected a strain of EF (LY-9, Scleroderma citrinum 1) whose growth was unaffected by exogenous IBA, and determined the optimal concentration of IBA that promotes LR development. Results indicated that (1) exogenous IBA did not significantly increase CR; (2) both IBA application and EF inoculation enhanced seedling height, root collar diameter, biomass, and root tips. Notably, EF inoculation had a greater promoting effect on seedlings N, P, and K uptake than IBA addition. EF inoculation increased IAA, IBA, and GA3 content while reducing ABA content in roots and leaves. However, IBA uniquely reduced strigolactone (SLs) content in roots without affecting ABA or GA3; (3) both IBA addition and EF inoculation downregulated the auxin response factor ChARF18, but only EF induced upregulation of the symbiotic signaling gene ChNORK. These results indicated that exogenous IBA does not enhance EF colonization rate, and that both exogenous IBA and EF improve plant growth, albeit via different physiological and molecular strategies.

[Objective]To study the phenotype of disease-resistant superior plants in the offspring of'Youza 2'×'Haiyou 3',so as to provide a theoretical basis for the study of genetic variation of interspecific hybridization and the cultivation of excellent germplasm of Camellia oleifera.[Method]Ten disease-resistant and superior strains were selected from the F1 generation of Camellia oleifera with'Youza 2'as the female parent and'Haiyou 3'as the male parent,and their flower phenotypes were determined.Among the 10 excellent disease resistant plants,six of them were fruited,and their fruit phenotype and economic quality traits were determined and analyzed,and the scores were calculated by principal component analysis,and the optimal plants were selected.[Result]1)The flowering period of the 10 resistant plants and their male parent'Haiyou 3'was in winter,and the flowering period of the female parent'Youza 2'was spring,and the flowering period of the hybrid offspring was earlier than that of the male parent.The coefficient of variation of the 11 measured indexes,including floral appearance and pollen characteristics,ranged from 2.98%to 17.47%;2)The coefficient of variation of 26 measured fruit appearance,economy and quality traits among hybrid offspring ranged from 6.51%to 57.71%;3)Principal component analysis was performed on 14 indexes,including single fruit weight,fruit transverse and longitudinal diameter,peel thickness,etc.,and two principal components were extracted,with a cumulative contribution rate of 88.86%.The comprehensive ranking of 6 disease resistance results of the hybrid offspring was YH-10＞YH-7＞YH-2＞YH-5＞YH-4＞YH-1,of which YH-10 has the highest comprehensive score of 3.17.[Conclusion]After cross-breeding with'Youza 2'as the female parent and'Haiyou 3'as the male parent,the F1 generation of disease-resistant superior plants was rich in phenotypic variation among plants,and the F1 generation produced a disease-resistant large-fruited superior plant YH-10 with excellent traits of both parents(disease resistance and fruit economic traits significantly higher than those of the low parents),and its single fruit weight increased by 41.65 g compared with that of the female parent.

Camellia oleifera is an important woody oilseed crop, and petaloid male-sterile germplasm provides valuable female parents for hybrid breeding by reducing the need for manual emasculation. However, the molecular events linking stamen petaloidy with pollen abortion remain poorly understood. Here, we compared normal anthers of the cultivar ‘Huashuo’ (HS) with petaloid anthers of its male-sterile mutant (HSP) using RNA-seq, WGCNA, endogenous hormone profiling, cytological observation, PCD detection, and transient/heterologous functional assays. A total of 55,166 unigenes and 6454 DEGs were identified across the anther petaloidy gradient. Petaloid anthers showed elevated IAA and CTK levels, reduced GA₃ content, and altered expression of hormone-signaling genes, indicating that hormonal reprogramming is associated with anther identity transition. WGCNA highlighted CoAPETALA2 (CoAP2), an A-class floral identity gene, and CoCP1, a cysteine protease gene related to tapetal PCD, as candidate regulators. HSP anthers exhibited premature tapetal PCD at the microsporocyte stage, accompanied by H₂O₂ accumulation and increased CoCP1 expression. In Nicotiana benthamiana, ectopic expression of CoAP2 affected stamen development, CoAP1 promoted petaloid anther-like malformations, and CoCP1 overexpression disrupted anther locule formation and reduced pollen fertility. Our findings support a regulatory model in which altered A-class floral identity activity contributes to anther petaloidy, whereas CoCP1-associated premature tapetal PCD contributes to pollen abortion in C. oleifera.

Camellia oleifera Abel. is an important woody oil tree species in China, and increasing the content of polyunsaturated fatty acids (PUFAs), particularly α-linolenic acid (ALA), is critical for improving the quality of its oil. Fatty acid desaturase 7 (FAD7) is a key enzyme in ALA biosynthesis in plants. However, the allelic variation, functional role, and regulatory mechanisms underlying FAD7-mediated ALA accumulation in C. oleifera remain poorly understood. In the study, we cloned three homologous CoFAD7 genes: CoFAD7-1, CoFAD7-2, and CoFAD7-3 from C. oleifera 'Huashuo'. All three genes contained eight exons and seven introns, encoding 452 amino acids. Expression analysis revealed that CoFAD7 was highly expressed during the fruit maturation stage (258-333 DAP), correlating positively with seed ALA accumulation. Haplotypes analysis and transgenic experiments identified CoFAD7-G as a superior genotype associated with higher ALA content. Biochemical assays further showed that the transcription factor CoAP2-3 binds to the CoFAD7 promoter and activates its expression. These findings suggest that CoFAD7-G is a key determinant of ALA content, providing a theoretical basis for the early identification of high-ALA C. oleifera germplasm.

The growing demand for wood products and ecosystem services in Chinese fir plantations has led to longer rotation ages and density control practices, raising concerns about their impact on soil fertility. This study assessed soil fertility of Chinese fir plantations in Fujian, Jiangxi, and Sichuan Provinces using the Nemerow index. The effects of stand age and initial planting density on soil fertility were analyzed using statistical models. In Fujian and Jiangxi, soil fertility was significantly higher at 11 and 30 years than at 5 and 25 years, while in Sichuan, it was higher at 25 and 30 years than at 5 and 11 years. In Fujian, soil fertility was higher at 6667 trees ha⁻2 than at 1667 trees ha⁻2. No significant differences were observed in Jiangxi, while in Sichuan, soil fertility at 6667 trees ha⁻2 was significantly higher than at 5000 and 1667 trees ha⁻2, and soil fertility at 10,000 trees ha⁻2 exceeded that at 1667 trees ha⁻2. Soil fertility typically increased with stand age, especially in Fujian and Sichuan. Soil fertility also increased with initial planting density, especially in Jiangxi and Sichuan. A structural equation model (SEM) explained 88% of the variance in soil fertility, with stand age directly affecting soil fertility and soil organic matter mediating the effects of stand age and planting density. These findings suggest that adjusting rotation age and planting density could help improve soil fertility, offering practical implications for sustainable forest management in Chinese fir plantations.

Background Many plants, including those commonly found in the Fagaceae family, produce more flowers and ovules than mature fruits and seeds. In Castanea henryi, an ovary contains 16–24 ovules, but only one develops into a seed. The other ovules abort or otherwise fail to fully develop, but the reason for this is unknown. Such a strict reproductive screening mechanism is rare in plants. Methods In this study, controlled pollination scheme were adopted, and conventional paraffin embedding and semi-thin sectioning techniques, followed by microscopy, were used for cytological studies of ovule development in C. henryi. Results Pollination affected not only the process of ovule development, but also the proportion of ovules that formed mature embryo sacs. Approximately 53.53% of the ovules in the pollinated treatment developed normally, while only 16.55% of the ovules in the unpollinated treatment developed into mature embryo sacs with a seven-cell, eight-nucleated structure. Failure to form mature embryo sacs and the abnormal divisions of the zygote, respectively, were the reasons for the pre- and post-fertilization ovule failures. Our findings not only provide basic information on the reproductive biology and also information on seed production of C. henryi.

Aging is a limiting factor for adventitious root (AR) formation, the accumulation of metabolic inhibitors in mature cuttings may be the cause. Rejuvenation by basal pruning is considered an effective method to promote rooting in mature cuttings. However, its effectiveness in mature Castanea henryi, the key inhibitory as well as the mechanism cause difficulty in AR formation remains unclear. In this study, rejuvenation was conducted on 2-year-old (juvenile) and 8-year-old (mature) C. henryi. Results indicated that the AR rate of juvenile cuttings was significantly higher than that of mature cuttings, and rejuvenation did not significantly increase AR incidence. Widely targeted metabolomic analysis revealed that rejuvenation has a relatively small impact on metabolites, while age remains the main factor. Kaempferol-3-O-(6″-malonyl) galactoside (Lmdp004892, trifolin) might be an inhibitor. In vitro validation experiments indicated that a low concentration of trifolin significantly promoted AR formation in 2-month-old cuttings, whereas a higher concentration inhibited rooting. RT-qPCR analysis further revealed that genes involved in trifolin biosynthesis (ChPAL, ChCHI, and ChF3H) were significantly high expression in mature cuttings, but genes of polar auxin transport (ChPIN2, ChPIN3, ChABCB1, and ChAUX1), auxin signaling (ChIAA2, ChIAA3, ChGH3-1, and ChGH3-3) were significantly low expression in mature cuttings. Taking all these evidences into account, we propose that trifolin accumulation in mature C. henryi cuttings inhibits the polar auxin transport and auxin signaling, thereby causing difficulties in AR formation. Rejuvenation through basal pruning may not be effective for AR formation in mature C. henryi.

Native pollinators greatly contribute to plant yield, which underpins global food security. However, breeding significantly alters plant flower traits, and the effects of breeding-mediated flower trait changes on sustainable agroecosystem production via the plant–pollinator relationship is unclear. An economically important oilseed tree ( Camellia oleifera ) was considered in this study to resolve this critical question. Breeding based on fruit traits induced significant changes in flower anthesis and size, which subsequently affected the plant–native pollinator relationship and even the pollinator specialization of plants. Changes in anthesis decreased the interactions between plants and pollinators; smaller flowers decreased the attractiveness of plants to pollinators, while larger flowers decreased the pollen transfer efficiency of pollinators. Additionally, the pollen transfer efficiency of pollinators contributed more to the plant fruit set than the attractiveness of plants to pollinators. Thus, breeding may decrease the contribution of native pollinators to the fruit yield of plants, especially that of large-flowered varieties. Overall, breeding-mediated flower trait changes will diminish the contribution of native pollinators to sustainable production in agroecosystems, highlighting the importance of managed pollinators in future agroecosystem production. Additionally, we call for including pollination syndrome in domestication syndrome in future agriculture, ensuring sustainable agroecosystems for future food security.

Camellia hainanica, a newly identified species in Hainan Province, China, is an edible oil tree with low fruit set under natural pollination. This study examined the flowering dynamics and reproductive system of C. hainanica 'H4'. Flowering occurred from mid-October to late December, peaking in early November. Each flower produced 2,373,649 +/- 139,795 pollen grains. Stigmatic receptivity, measured via benzidine-hydrogen peroxide method, peaked during the initial and peak flowering phases. Orthogonal array experiments identified optimal pollen storage at'-80 degrees C, sealed & dry, and air drying', maintaining 93% viability after 5 h in vitro germination-significantly exceeding C. oleifera (70.47%-87.91%). Pollination experiments revealed partial self-compatibility, with geitonogamy yielding a lower fruit set than xenogamy. No fruit set occurred in direct bagging or emasculation without pollination, indicating reliance on cross-pollination. The pollen-ovule (P/O) ratio (114,117.76) and outcrossing index (OCI = 4) suggested a partially self-compatible, outcrossing breeding system dependent on pollinators. Floral visitation peaked at 10:00 and 14:00, with Apis cerana identified as the most effective pollinator. These findings demonstrate that low natural yield in C. hainanica stems from pollinator limitation and partial self-incompatibility. Strategic introduction of managed pollinators and inter-varietal planting are recommended to enhance cross-pollination efficiency.

Gibberellins (GAs) play important roles in regulating reproductive development, especially flower development. However, the regulation of GA metabolism and GA signaling component genes of flower bud development in Camellia oleifera is not entirely understood. In this study, 6-year-old C. oleifera 'Huashuo' was used as the experimental material. Exogenous GA3 and GA biosynthesis inhibitors, chlormequat chloride (CCC) and uniconazole (UCZ), were applied to investigate the flower development, levels of GA3, GA metabolism, and the expression of genes involved in GA signaling across the different treatments. Our results demonstrate that exogenous GA3 promoted flower bud growth and accelerated blooming, with the rate of petaloid-anther transformation reaching up to 64.11% during the peak blooming period. Cytological analysis showed that the anthers in the GA3-treated flowers exhibited abnormal longitudinal elongation 30 days after spraying, and gradually developed into petaloid anthers. KEGG analysis revealed that the GA3 treatment regulated the plant hormone signal transduction. The genes encoding DELLA protein accounted for the largest proportion (52.45%) of the gibberellin signal transduction pathway DEGs. GA3 enhanced gibberellin content by regulating the gibberellin biosynthesis gene CoGA20ox1 during early flower development, and GID1 also showed a significant response to GAs. Additionally, the expression of genes associated with flower development (FT, LFY, SOC1, SVP) and those involved in petaloid-anther (MADS-box family members AP1, AGL8) exhibited significant differences. These results elucidated the regulatory effects of gibberellins and their inhibitors on anther development via the GA pathway in C. oleifera, which provides a foundation for further investigation into the mechanism of flower development.

Castanea henryi (Ch) is an underexploited chestnut, has a higher starch content (47.58-56.94%) than other nuts (including C. mollissima, pine nuts, etc.) and is abundant in bioactive substances. Thus, Ch is expected to safeguard human health while relieving arable land pressure. However, there is a lack of a consolidated overview of health benefits and potential applications of Ch and its by-products. The Ch kernel is abundant in resistant starch (65.4% of starch) and polyphenols (1.03-1.07 mg/g), and has lipid-lowering, anti-diabetes, anti-inflammatory, and anti-cancer benefits, enabling it to develop functional products. Notably, severe kernel damage and browning deteriorate its quality during processing. In addition, numerous Ch by-products (such as shells, leaves, flowers, and wood) are often regarded as waste. However, Ch shells and leaves contain rich nutrients, such as polyphenols, flavonoids, proteins, and carbohydrates, which can directly produce functional products, plant substrates, and feedstuff. Meanwhile, the wasted Ch by-products can also indirectly produce some mushrooms, herbs, or animal products. This review integrates advanced knowledge on product development and processing of fleshy fruits, proposing innovative and practical strategies to achieve high-value utilization of Ch kernels and providing insights for the waste utilization of by-products, thereby unlocking their full industrial and health potential.

Plant breeding has long focused on improving economic traits, yet its unintended effects on plant–pollinator interactions remain largely overlooked. Here, we report that selective breeding in Camellia oleifera unexpectedly enhances petal blue fluorescence, altering its attractiveness to bees. Field assays and behavioral experiments demonstrated that visual cues, rather than floral scents, play a decisive role in pollinator visitation, with bees showing a strong preference for petals emitting bright blue fluorescence under ultraviolet (UV) light. All six widely cultivated varieties exhibited stronger blue fluorescence than wild C. oleifera , in which the petals were nearly non-fluorescent. Metabolomic profiling revealed that the enhanced fluorescence correlated with the accumulation of hydroxycinnamic acid derivatives, particularly 3-O-p-coumaroylquinic acid. These compounds, originally targeted for improving fruit and oil quality, were found to mediate the formation of petal fluorescence and spatial patterning. This breeding-mediated metabolic shift effectively transformed C. oleifera from an “anti-bee” species into a “bee-attraction” species, suggesting a reversal of its natural pollination syndrome. Our findings uncover a previously unrecognized ecological consequence of plant breeding, linking secondary metabolism with pollination ecology. Recognizing and harnessing such floral traits in future breeding programs may not only improve pollination efficiency but also offer a novel pathway toward sustainable agroecosystem design.

This study investigated the effects of planting density and site index on stand attributes and soil nutrients in mature Chinese fir [Cunninghamia lanceolata (Lamb.) Hook.] plantations across Fujian and Sichuan Provinces, elucidating the pathways through which these factors influence standing volume (SV). The results showed that (1) planting density significantly affected stand variables, with average diameter at breast height (ADBH) decreasing and SV initially increasing and then declining with higher density. The number of mortality plants (NMP) and actual stand density (ASD) both increased significantly with higher density. Average tree height (ATH) and dominant height (DH) responses varied by region, with ATH decreasing in Sichuan and DH decreasing in Fujian with higher density. (2) Planting density affected soil nutrients differently in the two provinces, with soil total potassium (TK) increasing in Fujian and phosphorus decreasing in Sichuan. (3) Site index was positively correlated with ATH and ADBH but negatively correlated with ASD and NMP. Its relationship with soil nutrients was province-specific: in Fujian, site index was negatively correlated with total phosphorus (TP) and positively correlated with TK and soil pH, while in Sichuan it was only positively correlated with TK. (4) Structural equation modeling revealed different regulatory pathways: in Fujian, planting density influenced SV through both ASD and soil nutrients, while in Sichuan it affected only through ASD. This study highlights the region-specific interactions between planting density, site index, stand structure, and soil nutrients, providing a foundation for optimized plantation management.

Plant symbiosis with ectomycorrhizal fungi (ECMF) promotes soil phosphorus (P) uptake, and studies have suggested that acid phosphatase (ACP) produced by ECMF promotes soil organic phosphorus (Po) mineralization and thus aids in plant P uptake. However, how the host plant plays a role, if any in this process, is not clear. We explored the response of the host plant, Castanea henryi, to phytate and its utilization mechanism after inoculation with Pisolithus orientalis LY-8. In this study, ECMF inoculation significantly enhanced plant biomass, and soil available phosphorus, labile organic phosphorus, moderately labile organic phosphorus content, and Po mineralization rate. After inoculation, the ACP activity of plant root tips was higher than the sum of the ACP secreted by uninoculated root tips and the ACP secreted by fungi. Besides, alkaline phosphatase, and root tip vigor were significantly increased after inoculation. Transcriptome sequencing and RT-qPCR revealed that the relative expression of ChACP genes, especially purple acid phosphatase (ChPAPs) and phosphorus transporter genes were significantly higher in the inoculated treatment than in the uninoculated treatment. These results indicate that ECMF can induce the expression of ChPAPs, thus affecting the secretion of ACP in the root system of C. henryi, which in turn strengthens the ability to mineralize soil Po and promotes plant growth. Our results provide new insights into the understanding of the mechanisms of the role of ECMF in plant P nutrient acquisition.

Northward expansion of economically essential plants is a vital strategy for enhancing agricultural productivity; however, it often results in reduced yields. This study systematically assessed the impact of translocating the high-value oilseed species Camellia hainanica from its native tropical habitat Sanya to the temperate cultivation area of Changsha, focusing on its reproductive processes, including flowering, pollination, and fruit development. Our findings revealed a 45-day delay in anthesis at the transplanted location, which was associated with notably lower average daily temperatures (7.89 °C in Changsha compared to 24.63 °C in Sanya) during the anthesis period. While floral longevity, stigma receptivity, and pollen viability remained comparable between sites, anther dehiscence was markedly delayed by three days after transplanting. Crucially, pollinator visitation during peak flowering plummeted by 92% compared to the levels in Sanya, and a 57% reduction in pollen deposition on stigmas occurred. Consequently, natural fruit sets in Changsha collapsed to 0%, significantly lower than those in Sanya, despite artificial cross-pollination achieving an 11% fruit set rate. These results and the pollination deficit coefficient (D = 1.00) all demonstrate that severe pollination deficits are the key limitation causing reproductive failure in northward-expanded C. hainanica orchards. Addressing these yield constraints necessitates targeted breeding for earlier flowering genotypes and implementing pollination management strategies.

Camellia oleifera (C. oleifera) is one of the most important economic oil species in China. This study established an efficient protocol for the induction and multiplication of embryogenic callus, and the isolation, purification and Polyethylene glycol (PEG) induced fusion of protoplasts in C. oleifera. It is shown that the embryogenic callus induction was best when nodular embryogenic structures were treated with the hormone of 1.5 mg/L 2,4-Dichlorophenoxyacetic acid (2,4-D) and 1.5 mg/L 6-Benzylaminopurine (6-BA) on Murashige and Skoog (MS) medium, and the highest induction rate of embryogenic callus was 18.82