Search Results (55)

Larix olgensis is a valuable timber species in northern China, typically propagated through somatic embryogenesis (SE). However, long-term subculture can lead to a loss of embryogenic potential. This study aimed to establish a simple and stable protocol for the cryopreservation and regeneration of L. olgensis embryogenic callus (EC) that preserves its SE potential and regenerative capacity. The slow-freezing method was employed for cryopreservation. A cryopreservation protocol for L. olgensis EC was developed by optimizing the preculture duration and conditions, cryoprotectant composition and thawing temperature. The results showed that optimal outcomes were achieved using a 24 h stepwise preculture on medium containing 0.2 and 0.4 mol∙L⁻¹ sucrose, followed by cryoprotectant treatment with 0.4 mol∙L⁻¹ sucrose, 2.5% (v/v) dimethyl sulfoxide (DMSO) and 10% polyethylene glycol 6000 (PEG₆₀₀₀), and thawing at 37 °C. EC cryopreserved using this protocol achieved a 100% recovery rate. Moreover, the cryopreserved recoverable EC successfully underwent SE, progressing through germination and rooting. Cryopreservation duration (storage duration in liquid nitrogen) did not affect cell viability and proliferation rate, confirming the protocol’s suitability for long-term cryopreservation of L. olgensis EC. This study provides a valuable reference for the cryopreservation and regeneration of L. olgensis EC, with potential applications for other coniferous species. It establishes a robust foundation for the large-scale propagation of conifers. Full article

Larch shoot blight, caused by Neofusicoccum laricinum, threatens global larch resources, while conventional chemical control is constrained by pollution and resistance. To address this gap, we integrated metabolomics, transcriptomics, and antifungal efficacy assays to identify Fraxetin, a disease-induced phytoalexin, and to elucidate its antifungal activity and mechanism. Metabolomics showed infection-triggered accumulation of Fraxetin in resistant Larix olgensis shoots. Antifungal experiments showed that within the range of 68–1088 μg/mL, the optimal antifungal concentration was 1088 μg/mL. When inoculated larches were treated with 1088 μg/mL Fraxetin, the maximum inhibition rate of pathogen growth reached 66.67% within 12 days, and the symptoms of the treated plants were alleviated. Transcriptomics revealed activation of damage responses, disruption of oxidative homeostasis, and compromised membrane integrity in the pathogen under Fraxetin treatment. Physiological measurements confirmed increased lipid peroxidation, redox collapse, membrane leakage, and reduced fungal viability. These findings indicate a lipid peroxidation–mediated oxidative–membrane mode of action and support the potential of plant-derived Fraxetin for more sustainable management of larch shoot blight. Full article

Long-term subculture of embryogenic callus leads to a decline in somatic embryogenesis and germination capacity, which may be associated with increased methylation levels. 5-Azacytidine (5-AzaC), a methylation inhibitor, modulates DNA methylation and is widely involved in regulating plant growth, development, and metabolism. In order to investigate the effect of 5-AzaC on somatic embryogenesis and germination in Larix olgensis, we supplemented the proliferation medium with different concentrations of 5-AzaC. The results showed that the addition of 5-AzaC inhibited the proliferation of embryogenic callus, with the proliferation of embryogenic line N2 completely inhibited at 100 μM, while that of embryogenic line N4 ceased at 20 μM. In contrast, treatment with 10 μM and 20 μM of 5-AzaC significantly increased the somatic embryo yield in both embryogenic lines, with the peak yield observed at 20 μM for embryogenic line N2 and at 10 μM for embryogenic line N4. Furthermore, the addition of 10 μM 5-AzaC effectively reduced the deformity rate during somatic embryo germination in embryogenic line N2 and N4, by 15.91% and 13.53%, respectively. These findings demonstrate that 5-AzaC can partially restore the somatic embryogenesis potential of embryogenic callus in L. olgensis under long-term subculture. Additionally, these results suggest that its effects may be both concentration-dependent and genotype-specific. The results provide a potential approach to mitigating the decline in embryogenic competence, while also demonstrating significant potential for large-scale propagation. Full article

Climate change and injudicious nitrogen addition alter the soil physico-chemical properties and microbial activity in oligotrophic forest soil, which disrupts the nitrogen cycle balance. Nevertheless, recommended fertilizer forms and levels are considered to be crucial for stable nitrogen application. We established a short-term field trial for the first time using a randomized complete block design under the yellow larch forest, with six treatments applied, including urea CO(NH₂)₂, ammonium chloride NH₄Cl, and sodium nitrate NaNO₃ at concentrations of 10 and 20 kg N hm⁻² yr⁻¹, each extended by three replicates. The gene abundances were measured using quantitative PCR (qPCR), in which the abundance levels of AOA (amoA) and nirS were higher under high CO(NH₂)₂ 2.87 × 10¹⁰ copies g⁻¹ dry soil and low NO₃⁻ 8.82 × 10⁹ copies g⁻¹ dry soil, compared to CK, representing 2.8-fold and 1.5-fold increases, respectively. We found niche partitioning as revealed despite AOA (amoA) increasing in number, AOB (amoA) contributing more to ammonia oxidation while nirS proved opportunistic under stress conditions. This was supported by distinct significant correlations among factors, in which soil urease enzymatic activity (S-UE) was associated with AOA (amoA) and nirK, while AOB (amoA) and nirS positively correlated with NH₄⁺ content and soil potential of hydrogen (pH), respectively. Among the applied treatments, high-level NO₃⁻ increased total nitrogen content and had a significant effect on soil N-acetyl-β-d-glucosaminidase (S-NAG) and soil acid protease (S-ACPT) activity. In summary, we observed an increase in Larix olgensis growth with high nitrogen retention. Full article

Accurate segmentation of fine roots in field rhizotron imagery is essential for high-throughput root system analysis but remains challenging due to limitations of traditional methods. Traditional methods for root quantification (e.g., soil coring, manual counting) are labor-intensive, subjective, and low-throughput. These limitations are exacerbated in in situ rhizotron imaging, where variable field conditions introduce noise and complex soil backgrounds. To address these challenges, this study develops an advanced deep learning framework for automated segmentation. We propose an improved U-shaped Convolutional Neural Network (U-Net) architecture optimized for segmenting larch (Larix olgensis) fine roots under heterogeneous field conditions, integrating both in situ rhizotron imagery and open-source multi-species minirhizotron datasets. Our approach integrates (1) a Convolutional Block Attention Module (CBAM) to enhance feature representation for fine-root detection; (2) an additive feature fusion strategy (UpAdd) during decoding to preserve morphological details, particularly in low-contrast regions; and (3) a transfer learning protocol to enable robust cross-species generalization. Our model achieves state-of-the-art performance with a mean intersection over union (mIoU) of 70.18%, mean Recall of 86.72%, and mean Precision of 75.89%—significantly outperforming PSPNet, SegNet, and DeepLabV3+ by 13.61%, 13.96%, and 13.27% in mIoU, respectively. Transfer learning further elevates root-specific metrics, yielding absolute gains of +0.47% IoU, +0.59% Precision, and +0.35% F1-score. The improved U-Net segmentation demonstrated strong agreement with the manual method for quantifying fine-root length, particularly for third-order roots, though optimization of lower-order root identification is required to enhance overall accuracy. This work provides a scalable approach for advancing automated root phenotyping and belowground ecological research. Full article

Specialized research on large trees in Northeast China is rare. To strengthen the understanding of local large trees, a survey of 4055 tree individuals from 75 plots in southeastern Jilin Province was conducted. The individual number and species composition of large trees in the community, as well as large individual standards in diameter at breast height (DBH) and population structures of typical tree species, were analyzed. By setting a DBH ≥ 50 cm as the threshold, 155 individuals across all the recorded trees were determined as large trees in the community, and 32.9% (51/155) of them were national second-class protected plant species in China. By setting the top 5% in DBH of a certain tree species as the threshold of large individuals of that tree species, the large individual criteria of six typical tree species were determined. The proportion of basal area of large trees to all trees was 30.4%, and the mean proportion of basal area of large individuals across the six typical tree species was 23.9% (±4.0%). As for the population characteristics, Abies nephrolepis and Picea jezoensis had large population sizes but relatively thin individuals, Tilia amurensis and Pinus koraiensis had small population sizes but relatively thick individuals, while Betula costata and Larix olgensis had medium population sizes and medium-sized individuals. Full article

NAC transcription factors are a kind of plant specific transcription factor widely distributed in plants, and they play an important role in the process of plant growth and development. According to the transcriptome data, a transcription factor with typical NAC characteristics was isolated from Larix olgensis (common name “Dahurian larch”), that we named LoNAC5. The length of the coding sequence (CDS) was 1164 bp, encoding 387 amino acids. The LoNAC5 protein harbors a NAM (NAC family) domain at the 14–139 aa region of its N-terminus and an activation domain at the 324–364 aa region of the C-terminus. Phylogenetic tree analysis revealed that LoNAC5 belonged to the ATNAC3 subgroup. Cis-acting element analysis showed that there were multiple plant stress-resistance-related elements on the promoter of LoNAC5, including hormone and light responsiveness elements. LoNAC5 was localized in the nucleus by injection transformation of tobacco leaves. Results suggested that the LoNAC5 protein is active as a homodimer and that it binds to the GATGTG motif. The results of RT-qPCR showed that LoNAC5 is a highly expressed gene in L. olgensis, and the expression level is highest in 180-day needles. LoNAC5 responded to various hormone treatments and was induced by drought and salt stress. The yeast phenotype test showed that overexpression of LoNAC5 could make yeast grow better under drought and salt stress. It was speculated that LoNAC5 might act in L. olgensis as a positive regulator of drought and salt tolerance. Full article

Herein, we explored the ecologic niches of generalist and specialist species within the subalpine vegetation zone, a habitat of Abies sp. distributed throughout South Korea and China. We included Abies sp. habitats in inland areas of South Korea and parts of the Manchurian region of China. Rhododendron schlippenbachii Maxim., Acer pseudosieboldianum (Pax) Kom., Picea jezoensis (Siebold & Zucc.) Carrière, Betula ermanii Cham., Acer komarovii Pojark., Pinus koraiensis Siebold & Zucc., Betula davurica Pall., Betula costata Trautv., Quercus mongolica Fisch. ex Ledeb, and Sorbus commixta Hedl. were selected as generalist species. Betula chinensis Maxim., Betula platyphylla var. japonica (Miq.) H. Hara, Euonymus pauciflorus Maxim., Salix maximowiczii Kom., Cornus walteri F.T. Wangerin, Carpinus laxiflora (Siebold & Zucc.) Blume, Populus davidiana Dode, Philadelphus tenuifolius Rupr. & Maxim., Rhododendron brachycarpum D. Don ex G. Don, and Larix olgensis var. koreana (Nakai) Nakai were selected as specialist species. NMS ordination analysis showed that specialist, generalist, and other plant species distribution correlated with basal area at breast height, stand density, and species diversity index. Generalist species could be grouped based on Quercus sp., Betula sp., and Acer sp. niche spaces. Specialist species shared ecological niches with plant species found in the limestone zone, sedimentary rock zone, and valley area. Full article

Neofusicoccum laricinum is the causal agent of larch shoot blight, a fungal disease affecting several species of larch. It causes severe damage, including stunting and mortality. This study aims to address the severe impact of larch shoot blight by evaluating the effect of farrerol on the inhibition of Neofusicoccum laricinum in Larix olgensis. We used LC-MS/MS and weighted gene co-expression network analysis to investigate farrerol’s effects on Neofusicoccum laricinum and identify associated genes in resistant and susceptible larch. Our study identified significant differences in metabolite profiles between resistant and susceptible cultivars, with higher concentrations of farrerol showing complete inhibition of N. laricinum. Additionally, specific genes associated with farrerol content were up-regulated in resistant larch. Farrerol at higher concentrations completely inhibited N. laricinum, showing a strong correlation with increased disease resistance. This research suggests that farrerol enhances disease resistance in larch and provides a foundation for developing disease-resistant larch varieties based on antifungal metabolite traits. Full article

Needles play key roles in photosynthesis and branch growth in Larix olgensis. However, genetic variation and SNP marker mining associated with needle and branch-related traits have not been reported yet. In this study, we examined 131 samples of unrelated genotypes from L. olgensis provenance trails. We investigated phenotypic data for seven needle and one branch-related traits before whole genome resequencing (WGRS) was employed to perform a genome-wide association study (GWAS). Subsequently, the results were used to screen single nucleotide polymorphism (SNP) loci that were significantly correlated with the studied traits. We identified a total of 243,090,868 SNP loci, and among them, we discovered a total of 161 SNP loci that were significantly associated with these traits using a general linear model (GLM). Based on the GWAS results, Kompetitive Allele-Specific PCR (KASP), designed based on the DNA of population samples, were used to validate the loci associated with L. olgensis phenotypes. In total, 20 KASP markers were selected from the 161 SNPs loci, and BSBM01000635.1_4693780, BSBM01000114.1_5114757, and BSBM01000114.1_5128586 were successfully amplified, were polymorphic, and were associated with the phenotypic variation. These developed KASP markers could be used for the genetic improvement of needle and branch-related traits in L. olgensis. Full article

Forest defoliating pests are significant global forest disturbance agents, posing substantial threats to forest ecosystems. However, previous studies have lacked systematic analyses of the continuous spatiotemporal distribution characteristics over a complete 3–5 year disaster cycle based on remote sensing data. This study focuses on the Dendrolimus superans outbreak in the Changbai Mountain region of northeastern China. Utilizing leaf area index (LAI) data derived from Sentinel-2A satellite images, we analyze the extent and dynamic changes of forest defoliation. We comprehensively examine the spatiotemporal patterns of forest defoliating pest disasters and their development trends across different forest types. Using the geographical detector method, we quantify the main influencing factors and their interactions, revealing the differential impacts of various factors during different growth stages of the pests. The results show that in the early stage of the Dendrolimus superans outbreak, the affected area is extensive but with mild severity, with newly affected areas being 23 times larger than during non-outbreak periods. In the pre-hibernation stage, the affected areas are smaller but more severe, with a cumulative area reaching up to 8213 hectares. The spatial diffusion characteristics of the outbreak follow a sequential pattern across forest types: Larix olgensis, Pinus sylvestris var. mongolica, Picea koraiensis, and Pinus koraiensis. The most significant influencing factor during the pest development phase was the relative humidity of the year preceding the outbreak, with a q-value of 0.27. During the mitigation phase, summer precipitation was the most influential factor, with a q-value of 0.12. The combined effect of humidity and the low temperatures of 2020 had the most significant impact on both the development and mitigation stages of the outbreak. This study’s methodology achieves a high-precision quantitative inversion of long-term disaster spatial characteristics, providing new perspectives and tools for real-time monitoring and differentiated control of forest pest infestations. Full article

Atmospheric nitrogen deposition can alter soil microbial communities and further impact the structure and function of forest ecosystems. However, most studies are focused on positive or negative effects after nitrogen addition, and few studies pay attention to its interruption. In order to investigate whether interruption after different levels of short-term N additions still benefit soil health, we conducted a 2-year interruption after a 4-year short-term nitrogen addition (10 and 20 kg N·hm⁻²·yr⁻¹) experiment; then, we compared soil microbial diversity and structure and analyzed soil physicochemical properties and their correlations before and after the interruption in Larix olgensis forest soil in northeast China. The results showed that soil ecological stabilization of Larix olgensis forest further improved after the interruption compared to pre-interruption. The TN, C:P, N:P, and C:N:P ratios increased significantly regardless of the previous nitrogen addition concentration, and soil nutrient cycling was further promoted. The relative abundance of the original beneficial microbial taxa Gemmatimonas, Sphingomonas, and Pseudolabrys increased; new beneficial bacteria Ellin6067, Massilia, Solirubrobacter, and Bradyrhizobium appeared, and the species of beneficial soil microorganisms were further improved. The results of this study elucidated the dynamics of the bacterial community before and after the interruption of short-term nitrogen addition and could provide data support and a reference basis for forest ecosystem restoration strategies and management under the background of global nitrogen deposition. Full article

Forests are affected by a wide range of disturbances globally, resulting in the decline or death of large areas of them. There is a lack of comparative studies on how soil properties change in forests that die under the influence of disturbances, especially considering different levels of disturbance. For this study, we took Larix olgensis—a major plantation forest species in northeast China—as the research object, one in which a large outbreak of bark beetle led to large-scale forest death, and set up fixed sample plots characterized by different disturbance intensities. We investigated the responses of soil physicochemical properties and microbial community compositions to different disturbance intensities through the determination of soil nutrient indices and high-throughput sequencing. The results show that there were significant differences (p < 0.05) in the effects of different disturbance intensities on soil physicochemical properties, where the soil moisture content, total nitrogen, total carbon, and total phosphorus in the control group were significantly higher than those in the disturbed groups. The soil pH was highest under low-intensity disturbance and the soil total potassium content was highest under high-intensity disturbance. At different disturbance intensities, the highest soil moisture content was found in the high-intensity group. Proteobacteria, Actinobacteria, Verrucomicrobia, Acidobacteria, Candidatus_Rokubacteria, Chloroflexi, Gemmatimonadetes, and Thaumarchaeota were the dominant populations with higher abundances; meanwhile, the relative abundance of Bacteroidetes, Tenericutes, and a tentatively unclassified fungus differed significantly (p < 0.05) across disturbance intensities. Among the dominant microbial populations, Acidobacteria showed a significant negative correlation with soil pH and a significant positive correlation with total potassium content, Thaumarchaeota showed significant positive correlations with soil moisture content and total nitrogen content, and Firmicutes and Gemmatimonadetes showed significant negative correlations with total carbon content in the soil. Furthermore, soil total nitrogen content was the key factor driving changes in microbial communities. The results of this study provide a scientific basis for the study of the long-term effects of tree mortality caused by insect pests on soil microbial communities and their response mechanisms, which is of great theoretical value for the establishment of scientific and effective methods for woodland restoration. Full article

Larch is widely distributed throughout the world and is an important species for timber supply and the extraction of industrial raw materials. In recent years, the hybrid breeding of Larix kaempferi and Larix olgensis has shown obvious heterosis in quick-growth, stress resistance and wood properties. However, its growth and development cycle is too long to meet general production needs. In order to shorten the breeding cycle, we have for the first time successfully established and optimized a somatic embryogenesis system for Larix kaempferi × Larix olgensis. We found that the highest rate of embryonal-suspensor mass (ESM) induction was observed when late cotyledonary embryos were used as explants. The induced ESMs were subjected to stable proliferation, after which abscisic acid (ABA) and polyethylene glycol (PEG) were added to successfully induce somatic embryos. Treatment with PEG and ABA was of great importance to somatic embryo formation and complemented each other’s effect. ABA assisted embryo growth, whereas PEG facilitated the formation of proembryo-like structures. On top of this, we studied in more detail the relationship between redox homeostasis and the efficiency of somatic embryogenesis (frequency of ESM induction). During subculture, we observed the gradual formation of three distinct types of ESM. The Type I ESM is readily able to form somatic embryos. In contrast to type I, the type III ESM suffers from severe browning, contains a higher level of hydrogen peroxide (H₂O₂) and demonstrates a decreased ability to form somatic embryos. External treatment with H₂O₂ decreased the somatic embryogenesis efficiency of Type I and type III ESMs, or the higher the exogenous H₂O₂ content, the lower the resulting somatic embryogenesis efficiency. We found that treatment with the H₂O₂ scavenger DMTU (dimethylthiourea) could significantly increase the somatic embryogenesis efficiency of the type III ESM, as a result of a decline in endogenous H₂O₂ content. Overall, these findings have contributed to setting up a successful somatic embryogenesis system for larch production. Full article

AP2/ERF is an important transcription factor family involved in physiological processes such as plant development and hormone signaling. In this study, based on the available transcriptome data of hybrid larch during floral induction, 13 DREB genes belonging to the AP2/EREBP family with complete CDS regions were identified through alignment using the NCBI website. We conducted a bioinformatics analysis on the gene sequences, examining their tissue specificity, response to hormone treatment, and response to environmental factors. The DREB genes in hybrid larch (Larix kaempferi × Larix olgensis) showed tissue-specific expression, with DREB7, DREB8, DREB10, DREB12, and DREB13 exhibiting higher expression levels in nascent buds and higher expression in female cones compared to male cones. They also showed high expression during signal convergence and floral induction, and were highly expressed in materials with good fertility, suggesting their positive role in the cone-setting process of hybrid larch. Additionally, 13 DREB genes were all induced by abscisic acid (ABA), gibberellin 3 (GA₃), and indoleacetic acid (IAA), with the most pronounced expression changes observed after ABA treatment, indicating that these genes might be mainly regulated by ABA. In response to temperature and photoperiod treatments, DREB7, DREB8, DREB10, DREB12, and DREB13 showed significant responses, with increased expression levels induced by low temperature, while no clear pattern was observed after long or short-day treatments. These results of the study provide a reference for understanding the function of the DREB gene family in hybrid larch, offer a theoretical basis for inducing floral bud differentiation in hybrid larch, and contribute to a better understanding of the molecular mechanisms underlying cone-setting in hybrid larch. Full article