Lu Zhang

The application of organic fertilizer is an effective way to improve soil fertility and promote seedling growth. Toona fargesii (T. fargesii) is a fast-growing tree with high commercial value due to its excellent timber quality. However, the mechanism underlying its rapid growth at the seedling stage in red soil remains unclear. Here, we investigated the effects of cow manure application (OF group) on soil nutrients and rhizosphere microbial communities in red soil, as well as how it promotes the seedling growth of T. fargesii. Seedlings in the OF group showed a significantly higher specific growth rate than those in the unfertilized control (CK) group (73.51 ± 11.82% vs. 34.90 ± 5.49%, p = 0.022). This growth promotion was accompanied by an increase in soil pH (6.36 ± 0.01 vs. 6.22 ± 0.02, p = 0.001) and a concurrent decrease in NO₃⁻-N (10.60 ± 3.20 vs. 22.58 ± 3.49, p = 0.044). High-throughput sequencing demonstrated that cow manure tended to enhance bacterial diversity while decreasing fungal diversity. The OF treatment significantly enriched the relative abundances of bacterial phyla Myxococcota, Bacteroidota, Firmicutes, and Proteobacteria, while reducing Chloroflexi. For fungi, the relative abundances of Calcarisporiellomycota and Chytridiomycota were reduced under OF treatment. Redundancy analysis indicated that soil pH and organic matter (OM) content were the main environmental drivers shaping rhizosphere microbial communities. Our results demonstrated that short-term cow manure application raised soil pH and shifted the microbiome, coinciding with promoted seedling growth. This study provides insights into the microbiome-mediated rapid growth of tree seedlings in red soil. It implies that applying cow manure is an effective way to promote seedling performance in the early stages.

Objective This study aims to explore the relationship between the biomass investment patterns and the seedling quality index of different grades of Toona fargesii seedlings. Method The growth，morphological indexes and biomass of 468 annual seedlings of T. fargesii were measured when the seedlings stopped growing in winter.Factor analysis combined with the mean ± standard deviation method was employed to evaluate and classify the seedling quality index. Result （1） The results indicated that the ground diameter and seedling height of one-year-old T. fargesii seedlings were 1.37 cm and 145.37 cm，respectively.The total biomass and quality index of the seedlings were 59.93 g and 0.66，respectively.The coefficients of variation for growth traits and total biomass were both higher than 29.64%.The positive correlation coefficients between ground diameter and seedling height with biomass were 0.89 and 0.60，respectively，both reaching a highly significant level （P<0.01）.（2） Seedlings were classified into three grades based on diameter or height：Grade I seedlings （D≥2.00 cm，H≥203.96 cm）；Grade II seedlings （0.76 cm≤D<2.00 cm，88.16 cm≤H<203.96 cm）；and Grade III seedlings （D<0.76 cm，H<88.16 cm）.There were significant differences in biomass investment among the different grades of seedlings （P<0.05）.The aboveground biomass was consistently higher than the belowground biomass，indicating that T. fargesii seedlings tend to allocate more resources to aboveground growth to enhance seedling height and ground diameter development.（3） The fitted model assessing the relationship between growth quantity and total biomass for Grade II seedlings based on height was optimal，represented by the equation y=0.15x+4.73 with an R² value of 0.80.（4） The better the seedling grade （Grade I），the more significant the positive correlation between the seedling quality index and biomass，suggesting that seedlings with higher biomass possess higher quality. Conclusion The greater the biomass of T. fargesii seedlings，the higher their quality.Ground diameter and seedling height are two indicators that effectively reflect the total biomass of the seedlings.Classifying seedling grades based on these two indicators can provide a reliable evaluation of seedling quality.

Slash pine (Pinus elliottii Engelm.) is an economically significant tree species valued for its timber and resin production. Establishing a somatic embryogenesis system is essential for the effective utilization of slash pine. This study aims to develop an optimized cultivation system for the long-term proliferation of embryogenic callus (EC) in slash pine. The study used the EC induced from immature zygotic embryos as materials to investigated the effects of plant growth regulators (PGRs), subculture cycles, and subculture durations on the EC proliferation coefficient and the number of somatic embryos (SE). Additionally, we monitored the changes in the proliferation coefficient, the number of SE, and physiological and biochemical indicators of EC during long-term proliferation. The EC proliferation coefficient reached its highest value (7.65) when the DCR medium was supplemented with 1.0 mg/L 2,4-dichlorophenoxyacetic acid (2,4-D) and 1.0 mg/L 6-benzylaminopurine (6-BA). Refreshing the culture medium every 14 days, EC maintaining proliferation coefficient (4.05) and embryogenic potential for approximately three year (980 d), but the number of somatic embryos was low and significantly declined after 140 days.The additional supplementation of 1.0 mg/L 2- (1-naphthyl) acetic acid (NAA) to the original proliferation medium further enhanced SE induction, achieving a maximum of 143.25 SE per gram of EC. Under the optimal proliferation culture conditions, EC was subcultured for 392 days, with no significant differences observed in the proliferation coefficient and the number of SE. The results of correlation and path analyses between physiological indicators and proliferation coefficient indicate that the proliferation coefficient of EC is mainly related to the content of storage substances (starch and soluble sugars) and the activities of redox-related enzymes (POD and CAT). The optimized long-term proliferation culture system for EC in slash pine provides an efficient approach to enhance the production of EC and SE.

The nitrogen (N) and phosphorus (P) additions were commonly used to improve plantation quality. However, the balance between nutrient uptake in the underground part and nutrient utilization in the aboveground part of Pinus elliottii (Slash pine) plantation in subtropical regions after N and P addition is still unclear. We conducted the experiment using a randomized complete block design with four treatments: N (50 kg N ha⁻² yr⁻¹, P (100 kg P ha⁻² yr⁻¹), NP (N + P), and a control (CK). Nutrient transport dynamics of underground (rhizosphere soil and roots) and aboveground (twigs and needles) parts of a 10-year-old Pinus elliottii plantations were evaluated. The trial was maintained for three consecutive growing seasons. The results showed that N and P additions significantly increased the N, P, and potassium (K) contents of soils and plant tissues in subtropical slash pine plantation forests, and showed a significant and gradual increase in interannual variations over the observation period (except for TN in soils, which increased first and then decreased). In terms of nutrient transport and reabsorption efficiency, N addition promoted the transport of elemental P from the translocating root system to the twigs, whereas P addition inhibited this process. P addition significantly increased the nitrogen reabsorption efficiency (NRE) of the needles, but decreased the phosphorus reabsorption efficiency (PRE), showing an element-specific response to the nutrient reabsorption process. Structural equation modeling further revealed that N or P addition had direct positive effects on soil N, P, and K content (path coefficients r: 0.54, 0.71, 0.41). N addition indirectly negatively affected N resorption efficiency (NRE) and K resorption efficiency (KRE) (r: −0.62, −0.51) but positively affected PRE (r: 0.44). Conversely, P addition had an indirect negative effect on PRE (r: −0.59). These results reveal that in subtropical regions, slash pine plantations adapt to N or/and P addition by adjusting nutrient absorption, transport, and resorption efficiency. This provided new insights into nutrient transport and distribution strategies in underground and aboveground parts of plants under N or/and P additions.

Objective This study aims to investigate the genetic variation patterns of growth traits in half-sib families of Pinus elliottii plantations across multiple sites，with the goal of early selection of superior families for Pinus elliottii. Method Taking the 2-year-old progeny test forest of Pinus elliottii established in three places in Jiangxi Province as the object，the seedling height and ground diameter were investigated.Genetic parameters were estimated using the HalfsibMS package developed by the Key Laboratory of Forest Genetics and Breeding at Nanjing Forestry University.Comprehensive evaluation and early selection of 18 Pinus elliottii families were performed through breeding value estimation，multiple comparison methods，and comprehensive selection index methods，combined with uniformity indicators. Result The variation ranges of tree height and diameter traits in the 2-year-old progeny test forest of Pinus elliottii families were 43 to 198 cm and 0.8 to 6.2 cm，respectively，with genetic variation coefficients of 22.81% to 45.83%.The differences in tree height and diameter growth among families were highly significant （P<0.01），and there were interaction effects on growth traits among the three locations.The estimated genetic parameters indicated that the family heritability for tree height and diameter were 0.573 9 and 0.647 6，respectively，with individual heritability values of 0.108 9 and 0.184 7，indicating high family heritability，genetic stability，and minimal environmental influence.The breeding value estimation results showed differences in growth trait breeding values among Pinus elliottii families.Among them，the top 5 families in terms of tree height are Family No.3，4，6，1 and 5；the top 5 families in terms of ground diameter are Family No.4，1，3，2 and 6.By leveraging a joint selection strategy based on breeding values and comprehensive methods，families 3，4，2，and 6 were preliminarily identified as superior families.Based on breeding values and comprehensive index joint selection，families 3，4，2，and 6 were identified as superior families；further selection based on uniformity indicated that families 3，4，and 6 were the final selected superior families.Genetic gain estimates for the final selected three superior families showed height genetic gains and actual gains of 12.98%，12.1%，and 11.6%；and 20.04%，18.6%，and 17.94%，respectively.Ground diameter genetic gains and actual gains were 14.29%，9.13%，and 10.34%；and 24.9%，15.9%，and 17.97%，indicating their genetic advantages and application potentials. Conclusion Taking the breeding value as the main factor and combining it with other methods to carry out comprehensive evaluation and early selection can effectively screen out the excellent families that meet the breeding objectives.Combined with the results of the joint selection of breeding values，comprehensive selection indices and uniformity indices，the excellent half-sib families with high genetic gains，good comprehensive evaluations，high breeding values and excellent uniformity are Family No.3，Family No.4 and Family No.6，These families provide good germplasm material for subsequent genetic improvement and stand establishment of Pinus elliottii.

Introduction: Meliaceae, a significant group in Sapindales, possesses material and medicinal value due to its applications in timber and bioactive compounds. However, the high morphological diversity of the Meliaceae species and the lack of comparative studies of chloroplast (cp) genomes have led to great challenges in the classification and identification of Meliaceae species.Methods: In this study, we sequenced the complete cp genomes of three Toona species (Toona fargesii, Toona ciliata, and Toona sinensis), and conducted comparative analyses of these cp genomes along with 29 previously published cp genomes of Meliaceae. Additionally, we performed the phylogenetic analyses and estimated the divergence times of Meliaceae.Results: The cp genomes of 32 Meliaceae species ranged from 158,558 bp to 160,978 bp in length. Specifically, the cp genomes of Toona varied from 159,242 bp to 159,617 bp in length. These cp genomes contained a total of 135 unique genes, comprising 90 protein-coding, 8 rRNA, and 37 tRNA genes. Divergence time estimation revealed that the Meliaceae family diverged into two subfamilies (Cedreloideae and Melioideae) approximately 72.92 Ma (95% HPD: 60.62-87.01 Ma) in the Late Cretaceous. The diversification of Cedreloideae (47.86 Ma, 95% HPD: 47.42-48.22 Ma) occurred later than that of Melioideae (66.60 Ma, 95% HPD: 55.41-79.73 Ma). Furthermore, comparative genomic analysis identified 52 to 116 simple sequence repeats (SSRs) and twelve highly variable regions (HVRs) found among the cp genomes of Meliaceae.Discussion: Divergence time estimation indicates that most Meliaceae species have a relatively recent origin, with rapid divergence occurring during the Late Oligocene or Early Miocene epochs. Comparative analysis of cp genomes revealed that Meliaceae exhibits relative conservation in terms of cp genome size, inverted-repeat (IR) boundary, genome structure, HVRs and codon patterns. Although differences exist between the Cedreloideae and Melioideae subfamilies, the overall similarity remains notably high. Furthermore, the ycf1, trnK-rps16, and ndhF-rpl32 regions exhibited the highest nucleotide polymorphism within Meliaceae, while the rpl22 gene displayed significant genetic diversity within both subfamilies. As candidate molecular markers, these regions may effectively distinguish among species. These findings not only provide insights into the evolution and species identification but also establish a scientific foundation for future systematics within Meliaceae.

Frequent interspecific hybridization, unclear genetic backgrounds, and ambiguous evolutionary relationships within the genus Lycoris pose significant challenges to the identification and classification of hybrids, thereby impacting the application and development of Lycoris. This study utilizes karyotype structure, genome size, and fluorescent in situ hybridization (FISH) technology to explore the chromosomal evolution and hybrid identification of Lycoris employing three approaches at the cytogenetic level. The findings indicate that species with a smaller basic chromosome number exhibit less asymmetry than those with a larger basic chromosome number, suggesting that species with different basic chromosome numbers may have followed different evolutionary pathways. Lycoris aurea has a more symmetrical karyotype, which may be the plesiomorphic state, reflecting an evolutionary transition from symmetry to asymmetry in Lycoris chromosomes. Systematic clustering of 18 Lycoris species is consistent with chromosomal karyotype classification, primarily dividing into two groups: species with M + T + A type an M + T type as one group, and A type as another group. The average nuclear genome size (C-value) of the Lycoris genus is 22.99 Gb, with the smallest genome being that of L. wulingensis (17.10 Gb) and the largest being L. squamigera (33.06 Gb). Chromosome length is positively correlated with the C-value, and the haploid genome size (Cx-value) decreases with an increase in basic chromosome number (x). The FISH technique can quickly identify and authenticate artificial hybrids, thus inferring the parentage of natural hybrids. The study reveals the genetic background and interspecific relationships of 18 Lycoris species, identifies the authenticity of artificial Lycoris hybrids, and infers the possible parentage of natural hybrids, offering technical insights for the identification, classification, and genomic projects of Lycoris.

To explore the radial variation in wood properties of slash pine (Pinus elliottii Engelm.) during its growth process and to achieve the early prediction of these properties, our study was carried out in three slash pine harvest-age plantations in Ganzhou, Jian, and Jingdezhen, Jiangxi province of South China. Wood core samples were collected from 360 sample trees from the three plantations. SilviScan technology was utilized to acquire wood property parameters, such as tangential fiber widths (TFWs), radial fiber widths (RFWs), fiber wall thickness (FWT), fiber coarseness (FC), microfibril angle (MFA), modulus of elasticity (MOE), wood density (WD) and ring width (RD). Subsequent systematic analysis focused on the phenotypic and radial variation patterns of wood properties, aiming to establish a clear boundary between juvenile and mature wood. Based on determining the boundary between juvenile and mature wood, a regression equation was used to establish the relationship between the properties of juvenile wood and the ring ages. This relationship was then extended to the mature wood section to predict the properties of mature wood. Our results indicated significant differences in wood properties across different locations. The coefficients of variation for RD and MOE were higher than other properties, suggesting a significant potential for selective breeding. Distinct radial variation patterns in wood properties from the pith to the bark were observed. The boundary between juvenile and mature wood was reached at the age of 22. The prediction models developed for each wood property showed high accuracy, with determination coefficients exceeding 0.87. Additionally, the relative and standard errors between the measured and predicted values were kept below 10.15%, indicating robust predictability. Mature wood exhibited greater strength compared to juvenile wood. The approach of using juvenile wood properties to predict those of mature wood is validated. This method provides a feasible avenue for the early prediction of wood properties in slash pine.

Toona ciliata var. pubescens, known as “Chinese mahogany”, has high commercial value and is classified as a level II priority protected wild plant in China. However, due to overexploitation and its poor natural regeneration capacity, natural T. ciliata var. pubescens forests show varying degrees of decline in habitat adaptability. Arbuscular mycorrhizal fungi (AMF) symbiosis presents a potential strategy to enhance its regeneration. In this study, T. ciliata var. pubescens seedlings were inoculated with Septoglomus viscosum, followed by RNA-Seq analysis to compare gene expression differences between AMF-inoculated (AMI) and non-mycorrhizal (NM) treatments three months post-inoculation. A total of 16,163 differentially expressed genes (DEGs) were upregulated by AMF colonization, constituting 96.46% of the total DEGs. Specifically, 14,420 DEGs were exclusively expressed in the AMI treatment, while 35 DEGs were completely silenced. Most of the upregulated DEGs were located on the cell membrane, nucleus, and cytoskeleton and functioned in protein binding, S-adenosylmethionine-dependent methyltransferase activity, and lipid binding during cellular/macromolecule/protein localization, intracellular/protein transport, the cell cycle, and signal transduction. Additionally, lots of key genes related to oxidative stress responses, nutrient transport, and small GTPase-mediated signal transduction were found to be upregulated. These results suggest that AMF inoculation may enhance root cell growth by activating genes involved in nutrient uptake, stress responses, signal transduction, and substance transportation. This study elucidates the molecular mechanisms underlying the growth promotion of T. ciliata var. pubescens through AMF symbiosis, laying a foundation for the future application of AMF in its natural forest regeneration.

Toona fargesii (T. fargesii) is a deciduous tree of the Meliaceae family which is utilized for high-value timber. Interestingly, root sprouting is a typical reproductive pattern in T. fargesii. Nevertheless, the genetics underlying this phenomenon are still unclear. Here, three type of roots of T. fargesii were used for histological observation, plant endogenous hormone determination, non-structural carbohydrate (NSC) determination, and sequencing using the Illumina next-generation and PacBio SMRT platforms. Our results indicated that root sprouts originated from cork cambiums. Furthermore, indole-3-acetic acid (IAA), zeatin riboside (ZR), gibberellic acid 3 (GA3), and abscisic acid (ABA) content was significantly increased, while soluble sugar content was significantly decreased in the root sprouts. In addition, transcriptomic analysis suggested a total of 36.19 G of raw data from which 210 differentially expressed genes (DEGs) of were identified in RS vs. SR. Of these, the candidate DEGs were largely enriched in the citrate cycle, gluconeogenesis, starch and sucrose metabolism, and plant hormone signal transduction pathways. We therefore speculated that the accumulation of cytokinin and auxin might be induced by ATP-binding cassette-B 19 (ABCB19) and ABCG14, which were necessary for root sprouting. Additionally, transcription factors SQUAMOSA promoter binding protein-like 18 (SPL18) and NAM, ATAF1/2, and CUC2-14 (NAC14) were found in response to environmental water and epigenetic modification in RS. Overall, this study was to unravel the physiological and transcriptomic levels of the development of root sprouting in T. fargesii.