Flower bud differentiation marks a critical transition period in plants from vegetative to reproductive growth. During this process, flavonoids, a key class of secondary metabolites in plants, do not directly influence flower bud differentiation. Instead, they play a vital role in the morphogenesis and developmental regulation of flower buds, serving as an indispensable material foundation for the normal formation and development of floral organs. They regulate the internal environmental homeostasis required for mango axillary bud differentiation, creating suitable conditions for the transformation of axillary buds into flower buds. Through pathways such as adjusting hormone balance, mediating signal transduction, and maintaining stable cellular metabolism, they indirectly promote the transformation of mango axillary buds into flower buds with corresponding morphological and physiological characteristics. Building upon the research group’s prior findings, this study demonstrated that removing terminal flowers during mango axillary bud conversion could delay flowering. Flower bud differentiation marks a critical transition period in plants from vegetative to reproductive growth. During this process, flavonoid, a key class of secondary metabolites in plants, do not directly influence flower bud differentiation. Instead, they play a vital role in the morphogenesis and developmental regulation of flower buds, serving as an indispensable material foundation for the normal formation and development of floral organs. They regulate the internal environmental homeostasis required for mango axillary bud differentiation, creating suitable conditions for the transformation of axillary buds into flower buds. Through pathways such as adjusting hormone balance, mediating signal transduction, and maintaining stable cellular metabolism, they indirectly promote the transformation of mango axillary buds into flower buds with corresponding morphological and physiological characteristics. Building upon the research group’s prior findings, this study demonstrated that removing terminal flowers during mango axillary bud conversion could delay flowering. This technique effectively mitigates damage from late spring frosts and other cold weather events, offering a crucial technical approach for securing mango yields. To delve into the underlying regulatory mechanisms, axillary buds from the “Guifei” mango cultivar at the Gan Zhuang Town mango base in Yuanjiang county, Yuxi city, Yunnan province (23.4210°N, 102.57189°E) were used as the research material. Axillary buds were collected after apical inflorescence removal and subjected to integrated transcriptomic and metabolomic analysis. This study examined gene expression and metabolic changes related to flavonoid biosynthesis following terminal inflorescence removal, revealing the association between flavonoid biosynthetic pathways and floral bud differentiation to effectively mitigate spring frost damage in mangoes. Results indicated that post-removal, gene expression changes in flavonoid biosynthesis pathways, including CHS1, CHI, F3'H, F3'5'H1, and F3H, affected the production of naringenin chalcone, naringenin, dihydroquercetin, cyanidin, pelargonidin,(+)-gallocatechin,2ʹ,3,4,4ʹ,6ʹ-pentahydroxychalcone, and pinobanksin. This indicates that the CHS1, CHI, F3H, F3'H, and F3'5'H1 genes accelerate the conversion of mango axillary buds into floral buds by regulating flavonoid biosynthesis, thereby promoting the formation of mango floral organs and providing new insights into the association between flavonoid biosynthesis and floral bud differentiation.
Cassava (Manihot esculenta Crantz), a vital tropical food crop, exhibits significant sensitivity to low temperature, which severely restricts its cultivation range. Lignin is a key stress-resistant component in cell walls, playing a crucial role in plant adaptation to low temperature stress. However, the function of cinnamyl alcohol dehydrogenase (CAD), a pivotal enzyme in lignin biosynthesis, during low-temperature stress responses remains unclear. This study analyzed physiological phenotypes, CAD enzyme activity and lignin accumulation in cassava under low temperature stress. CAD enzyme activity was significantly increased by 66.7% and lignin content was also increased by 14.8% at the low temperature of 10 ℃. Transcriptome profiling identified MeCAD2 as the key gene responsive to low temperature stress. Heterologous expression of MeCAD2 confirmed that its encoded MeCAD2 protein possessed CAD enzymatic activity. Virus-induced gene silencing (VIGS) of MeCAD2 in cassava resulted in a 18.9% reduction in CAD enzyme activity and a 12.3%-22.4% decrease in lignin content. Furthermore, under low temperature stress, MeCAD2-silenced plants exhibited exacerbated leaf damage, a 172.5% increase in malondialdehyde (MDA) accumulation, and intensified reactive oxygen species (ROS) staining. The results indicate that MeCAD2 enhances cassava low-temperature tolerance by regulating lignin deposition. This study elucidated the critical role of MeCAD2 in cassava’s response to low-temperature stress, providing a novel candidate gene for molecular breeding.
Coffee, one of the most important economic crops worldwide, is widely cultivated in tropical and subtropical regions and serves as a major source of income for many countries and regions. Caffeine (1,3,7-trimethylxanthine) is the main metabolite in coffee beans and related products, which not only imparts the characteristic bitter taste and stimulates effect of coffee but also exerts multiple biological functions. The N-methyltransferase (NMT) gene family plays a key role in the caffeine biosynthetic pathway. Therefore, systematic identification of coffee NMT family members and analysis of the expression patterns at different developmental stages are of great importance for investigating caffeine metabolism, improving coffee quality, and breeding stress-resistant varieties. In this study, a total of 27 NMT genes were identified in allotetraploid Coffea arabica, including 14 genes from the C subgenome and 13 from the E subgenome, distributed across 10 chromosomes. Gene structure analysis revealed that family members shared similar motif compositions but differed in intron arrangement and number. Cis-acting element analysis showed that the promoters of C. arabica NMT genes were enriched with various regulatory elements related to light response, stress response and hormone signaling, and contained transcription factor binding sites such as MYB, MYC and W-box. Transcriptome analysis further demonstrated that NMT genes exhibited dynamic expression during fruit development, with the ripening stage showing the highest number of differentially expressed genes (14 703), while the expansion stage showed the lowest (4419). Moreover, C. arabica NMT genes displayed clear temporal and tissue-specific expression patterns. Weighted gene co-expression network analysis (WGCNA) identified 12 co-expression modules, among which the ivory, coral1 and darkolivegreen modules were enriched in pathways related to environmental stress and protein folding, energy metabolism and nucleic acid metabolism, respectively. Core gene network analysis revealed the critical roles of NMT genes in caffeine metabolism, stress response, and developmental regulation. Taken together, this study systematically identified the NMT gene family in allotetraploid C. arabica, characterized the expression patterns during different stages of fruit development, and elucidated the potential functional differentiation, thereby providing a theoretical basis for coffee breeding.
As an important ornamental flower, Cymbidium sinense needs to undergo a long period of low temperature dormancy during its flower development to achieve flowering. SHORT VEGETATIVE PHASE (SVP) is a key regulator in plant flowering pathway and plays an important role in plant dormancy and flowering. In this study, three SVP homologous genes, named CsSVP1, CsSVP2 and CsSVP3, were cloned from Xiaoxiang. The results of bioinformatics analysis showed that the full-length of the three CsSVPs genes were 651 bp, 687 bp and 714 bp, encoding 216, 228 and 237 amino acids, respectively, and all of them contained conserved MADS-box and K-box domains. Amino acid sequence alignment and phylogenetic analysis showed that CsSVP1 had the highest similarity with CgSVP, CsSVP2 and CsSVP3 had the highest similarity with EpMADS18 and DhcSVP, respectively. CsSVP1 was closely related to CgSVP of C. goeringii. CsSVP2 was closely related to EpMADS18, while CsSVP3 was closely related to DhcSVP. Promoter cis-element analysis showed that the CsSVPs gene contained many light response, hormone response and other elements. The results of qRT-PCR showed that the three CsSVPs genes were expressed in roots, stems, leaves, flowers and fruits of C. sinense. The expression patterns of CsSVP1 and CsSVP3 genes were similar, which were accumulated in leaves and stems, and the expression levels in flowers and fruits were significantly decreased. The expression of CsSVP2 was the highest in fruit, followed by leaves, stems and flowers, suggesting that their biological functions may be quite different. At the same time, the expression in different floral organs was detected, and it was found that the three CsSVPs had the highest expression in sepals. Furthermore, the expression of CsSVP2 gene in different flower development stages was also detected. It was found that the expression level of CsSVP2 gene was the highest in the S1 stage of early development, and decreased with the development of flower organs, and the expression level was the lowest in the S5 stage of mature flowers. The overall expression levels of CsSVP1 and CsSVP3 in floral organs were not high. The expression level of CsSVP1 was the highest in S2 period and the lowest in S5 period. The expression level of CsSVP3 was the lowest in S2 period, and the expression level continued to increase in the late stage of flower development. In addition, low temperature treatment found that the expression of CsSVP1 and CsSVP2 increased slightly after low temperature treatment, while CsSVP3 decreased significantly. In ABA treatment, only the expression of CsSVP1 was significantly inhibited, while CsSVP2 and CsSVP3 did not respond. The results suggest that different CsSVPs genes have different functions and may play different roles in the process of low temperature dormancy promoting flowering of orchids, which would provide an experimental basis for further analysis of the specific functions of SVP genes in the process of flower development.
Aquilaria sinensis, a plant belonging to the genus Aquilaria of the Thymelaeaceae family, can produce agarwood when exposed to natural factors (such as lightning strikes, fire, and insect bite) or artificial factors (such as cuts, holes, and inoculation of fungi). MADS is a transcription factor that plays a significant role in plant growth and development and stress response. However, its function in A. sinensis remains unclear. To elucidate the stress response of MADS-box genes in A. sinensis after injury, this study utilized transcriptomic data derived from A. sinensis to expression heatmaps and screen for differentially expressed genes, leading to the identification and cloning of a MADS-box encoding gene, designated AsMADS12, which exhibited significant differential expression. Comprehensive analyses were subsequently conducted on the domain architecture, physicochemical properties, phylogenetic relationships, and predicted secondary and tertiary structures of AsMADS12. The expression dynamics of the AsMADS12 at various time points after methyl jasmonate (MeJA) treatment were assessed via real-time quantitative PCR (RT-qPCR). Furthermore, subcellular localization of the AsMADS12 was determined by transiently expressing in onion epidermal cells (Agrobacterium-mediated infiltration) and observing fluorescence under a confocal laser scanning microscope. Sequence and evolutionary analyses revealed that AsMADS12 possessed a complete open reading frame (ORF) of 678 bp, encoding a protein of 255 amino acids. The predicted molecular weight of the encoded protein was 25.28 kDa. AsMADS12 contained a typical MEF2-like MADS domain and was classified as a MIKC-type transcription factor. The secondary structure of the protein was mainly composed of 52.00% α-helix, 11.56% extended chain, and 36.44% random coil. Phylogenetic cluster analysis revealed that AsMADS12 was clustered in the same branch as the MADS of Citrus sinensis and Citrus trifoliata. The subcellular localization experiment showed that the AsMADS12 protein was located in the nucleus. The real-time fluorescence quantitative results indicated that methyl jasmonate treatment could induce the expression of AsMADS12, and the expression level was the highest at 24 hours after treatment. It was speculated that AsMADS12 might play a potential role in the formation of agarwood in A. sinensis. This study completed the cloning of the gene for the first time and conducted preliminary exploration, laying the foundation for further research on whether it participates in the formation of agarwood and its role in biotic or abiotic stress responses, thereby providing a theoretical basis for understanding the molecular regulatory mechanism of agarwood formation in A sinensis.
Rubber tree (Hevea brasiliensis), an economically significant species, produces natural rubber, a strategic resource for China. Since rubber tree introduced from South America to Southeast Asia in the 19th century, rubber tree productivity has been substantially improved through sustained genetic improvement. This article comprehensively reviewed the botanical characteristics of the rubber tree, traced its history of introduction and domestication, and analyzed the current applications, achievements, challenges, and future research directions of both conventional breeding techniques (including hybrid breeding, polyploid breeding, mutagenesis breeding, etc.) and modern biotechnological breeding techniques (including molecular marker-assisted selection, genomic selection, genetic modification, gene editing, etc.) in rubber tree improvement. The review aims to provide a reference for researchers in rubber tree genetics and breeding, facilitate progress in this field, and promote the sustainable development of the natural rubber industry.
Hainan oil-tea Camellia (locally termed Shanyou in Hainan) is a regionally endemic decaploid species thriving under monsoonal tropical climatic conditions, which confers its distinctive flavor profile and quality attributes. This paper summarized recent research on Shanyou, examining its evolutionary distribution, growth traits, the exceptional quality characteristics of the oil, and methodologies for germplasm identification. Furthermore, strategic recommendations were proposed to advance the development of the Hainan Shanyou industry, in order to provide a critical foundation for subsequent research, product development, and the establishment of a premium Shanyou oil brand, thereby facilitating the distinctive development of the regional industry.
Hainan Island possesses unique ecological conditions that nurture abundant wild tea resources. This study systematically investigated the distribution patterns and growth models of wild tea trees in Hainan through literature review and field surveys. Curvilinear regression analysis was employed to establish growth relationships among tree height (H), crown width (P), diameter at breast height (DBH, D), and basal diameter (d). Wild tea populations are distributed in Wuzhishan City, Baoting County, Qiongzhong County, Baisha County, Ledong County, and Lingshui County, spanning longitudes 108.85°E-109.91°E, latitudes 18.21°N-19.19°N, and elevations 357.0-1410.6 m. The population primarily occur in secondary forests and cultivated tea gardens, with significant canopy density fluctuations. The wild tea tree resources in the study area were mainly distributed in sheets, and 6915 wild tea trees were preliminarily investigated in 6 cities and counties, and the area with the largest number of wild tea trees was Wuzhishan, with a total of 4461 trees, accounting for 64.51% of the total. Wild tea tree diameter structure showed a normal distribution characteristic with grade II seedlings accounting for the main body (40.68%), followed by grade I seedlings (25.29%), and only 2.22% of the V-VI. large-diameter wild tea trees remaining, showing an obvious juvenile structure. Maximum crown width (11.5 m) and tree height (26.0 m) were recorded in Wuzhishan City, alongside the highest coefficients of variation for crown width (56.53%) and height (53.87%), with a crown-to-height ratio of 0.62. Optimal cubic regression models for growth relationships were: H=0.614+0.014C−0.258C2+2.13C3 (R2=0.488, h<700 m); H=1.949−0.001D+0.020D2+ 0.248D3 (R2=0.340, 700 m≤h<1300 m); D=−0.726+0.001d−0.024d2+1.026d³ (R2=0.887, h≥1300 m). The research would provide critical data for ecological monitoring in Hainan Tropical Rainforest National Park, tea germplasm conservation, and green certification of tea industries. It also would advance carbon sink management under China’s carbon neutrality goals and highlights the urgency for scientific conservation and sustainable utilization of wild tea resources to enhance biodiversity and regional socioecological resilience.
Intercropping within rubber plantations presents an effective strategy to counteract the financial challenges posed by sustained low prices of natural rubber and widespread cultivation losses. The success of the intercropping systems is critically dependent on understory light availability, which serves as a key driving factor. A thorough analysis of the variations in understory light conditions among different rubber clones and the underlying causes is essential for providing a theoretical basis for optimal clone selection and system design. This study investigated rubber plantations featuring various clones, tree ages, and planting patterns. The understory light intensity were measured and compared. Unmanned Aerial Vehicle LiDAR point clouds were used to extract key tree architecture parameters to determine the architectural drivers of light variability. Findings revealed significant differences in understory light intensity attributable to clone type, tree age, and planting pattern. Notably, the Reken 628 clone consistently provided significantly higher understory light levels across all ages and row orientations compared to other clones like CATAS 72059, and CATAS 73397. UAV-derived data confirmed that Reken 628 plantations exhibited larger inter-row gaps and significantly lower canopy closure. Architectural analysis further elucidated that Reken 628 was characterized by a taller stature, higher branching, a smaller crown length ratio, and a more compact, sparser crown structure with fewer, smaller-angled primary branches. This clone also displayed pronounced natural self-pruning, which collectively contributes to its low canopy closure. Conversely, CATAS 73397 features a wider crown, a higher crown length ratio, more numerous and wider-angled branches, and severe crown overlap, resulting in high canopy closure. In conclusion, considering its favorable tree architecture and the resultant superior light conditions, Reken 628 is identified as an excellent clone for intercropping systems. This research holds significant practical value for advancing the adoption and sustainable development of intercropping in rubber plantations.
The absence of standardized protocols for harvesting green betel nut fruits has led to significant inconsistencies in the quality of fresh produce. Therefore, this experiment used Hainan betel nuts as the test material, sampling every 30 days starting from 30 days after fruit setting, measuring the developmental dynamics of fruit phenotype and inclusions, exploring the development law of betel nut fruits, and determining the optimal harvesting period for green betel nuts. The fruit shape index showed a trend of first increasing and then decreasing, with a variation range of 1.69−1.87. Among them, when the fruit developed to 120 days (1.79)−150 days (1.61), the fruit shape index met the first-grade standard, presenting a long elliptical shape. The chlorophyll content was high at 120−180 days, and the fruit color was emerald green. The pulp hardness showed a trend of first increasing and then decreasing, with a variation range of 85.2−274.49 gf. The hardness at 120−150 days was lower than the average (197.34 gf), meeting the first-grade standard. The soluble sugar contents in both the pulp and kernel showed a trend of first increasing and then decreasing, with variation ranges of 1.23%−4.47% and 5.56%−7.12%, respectively. The soluble sugar contents in the pulp and kernel were high at 120−180 days. The arecoline contents in both the pulp and kernel showed a gradual decreasing trend, with variation ranges of 3.55%−0.19% and 3.42%−0.40%, respectively. The arecoline content in betel nut fruits reached a relatively high level at 120−180 days. After standardizing the data for several key nodes and performing Principal Component Analysis (PCA), the comprehensive score of the pulp and kernel was the highest (1.18) at approximately 150 days after flowering. Combining the variation laws of fruit phenotype and internal quality, the optimal harvesting period for green betel nuts is approximately 150 days after fruit setting.
Fruit quality is the key indicator to measure the commodity value of fruit, and the indicators such as single fruit weight, fruit shape and fruit determination degree (DD) are particularly crucial, which directly affect consumers' desire to buy. In addition, primary metabolites are indispensable substances in the process of plant growth and development, which are widely present in all plants, providing basal metabolites and energy support for plant growth, development and reproduction. Primary metabolites such as sugars, organic acids, amino acids and inositol are the key factors affecting fruit quality, and they are also important criteria for measuring fruit flavor and texture. With the improvement of consumers' living standards and the pursuit of healthy fruits, a large amount of data is needed to screen out Annona squamosa varieties with high nutritional value and high sugar. Yunnan's hot and dry valley climate provides an excellent environment for the fruit to thrive. In order to explore the differences in fruit quality and the composition and content of primary metabolites in the pulp of the four varieties of A. squamosa in the dry and hot river valley of Yunnan Province, the varieties with high nutritional value and high sugar were screened. Four varieties (AP, Damu, Fengli and Liulian) from the planting base of Yuanjiang County, Yuxi City, Yunnan Province were used as the test materials. Gas chromatography-mass spectrometry (GC-MS) was used to determine the composition and content of primary metabolites per unit weight of fresh fruit pulp, and the one-way analysis of variance (ANOVA), principal component analysis (PCA) and partial least squares discriminant analysis (PLS-DA) were used for comprehensive analysis and evaluation. Among the four cultivars in the dry-hot valley area of Yunnan, AP A. squamosa had the largest single fruit weight. The content of soluble solids (TSS) in Liulian A. squamosa was the highest. The fruit shape of the Damu A. squamosa is oval, and the other three varieties are oblong; The fruit DD of Fengli A. squamosa was the smallest, and there was no significant difference among the other three cultivars. A total of 43 primary metabolites were detected in the pulp of the four cultivars, including 9 amino acids, 13 organic acids, inositol and 20 soluble sugars. Further analysis of the contents of various primary metabolites in the pulp of the four varieties showed that the contents of sucrose, fructose, glucose, allulose, citric acid and malic acid were the main among the 43 primary metabolites. The contents of glucose, allulose, citric acid and malic acid in Liulian A. squamosa were significantly higher than those of other varieties, and the contents of sucrose and fructose in AP A. squamosa were significantly higher than those of other varieties. In addition, some primary metabolites had significant cultivarity specificity, among which leucine, acetamide acid, xylulose and threonate were only detected in AP A. squamosa. Trehalose is only detected in Liulian A. squamosa. Principal component analysis (PCA) showed that the variance contribution rate of PC1 was 48.3%, that of PC2 was 25.8%, and that of cumulative variance was 74.1%. Partial least squares discriminant analysis (PLS-DA) was used to screen 19 primary metabolites as the characteristic differential metabolites in VIP≥1, including 5 amino acids, serine, L-hydroxyproline, leucine, L-norvaline and L-glutamic acid. 2 organic acids, acetamide and 2-ketoglutarate; 7 soluble sugars, namely D-(+)-xylose, D-arabinose, hexapyranose, xylulose, L-threonose, L-(-)-fucose, sucrose, d-galactose, D-(+)-pinedisinose, maltose and D-(+)-cellobiose; and inositol. From the perspective of basic quality and primary metabolite level, the fruit TSS and primary metabolite content of Liulian A. squamosa were the highest, while the TSS of Fengli A. squamosa was moderate and the outer gauge was the most regular. Therefore, the two varieties can be promoted and planted as A. squamosa varieties with high nutritional value and high sugar in dry and hot river valleys.
Date palm, a member of the palm family, is dioecious with highly heterozygous genes and severe trait segregation. The propagation of its seedlings depends on asexual reproduction. Tissue culture technology is currently the main approach to realize the commercial production of date palm seedlings. However, the low germination rate of somatic embryos and the long period of seedling formation lead to difficulties in system construction and high tissue culture costs. Therefore, studying the physiological responses of date palm to adventitious bud induction regulated by hormones and optimizing the adventitious bud induction system are urgent tasks. Based on the previous screening of explant types of date palm, an orthogonal experimental design was used to optimize the induction of callus and embryogenic callus. By screening and proportioning the types and concentrations of plant growth regulators in the MS medium, adventitious buds were induced from somatic embryos. The germination rate of adventitious buds and the induction time of buds were statistically analyzed. Date palm adventitious buds obtained under different hormone levels were sampled, and the morphological change patterns of adventitious buds were observed. The change patterns of antioxidant enzyme activities (peroxidase, superoxide dismutase, glutathione reductase, catalase), hydrogen peroxide content, and other indicators in the samples were determined. The results indicated that the bud induction rate was P8>P6>P5>P4. The highest bud induction rate was achieved under the P8 (MS+30 g/L sucrose+3 mg/L NAA+2 mg/L 6-BA+1 mg/L KT) treatment. The shortest bud induction time was under the P6 (MS+30 g/L sucrose+2 mg/L NAA+3 mg/L 6-BA+1 mg/L KT) treatment. The highest activity of glutathione reductase was under the P8 treatment. The coefficient of variation was the largest for the activity of glutathione reductase, and the range was the largest for the activity of superoxide dismutase. Principal component analysis revealed that the cumulative contribution rate of the first three principal components reached 94.614%. The eigenvalue of the first principal component was 2.365, with a contribution rate of 50.729%. In the first principal component, the activities of glutathione reductase, catalase, and peroxidase jointly affected, among which the eigenvalue of the activity of glutathione reductase was the largest at 0.821, mainly reflecting the influence of the activity of glutathione reductase on adventitious bud induction. The results of the study would provide a theoretical basis for optimizing the adventitious bud induction system and lay a technical foundation for achieving efficient and rapid propagation of date palm.
The study was aimed to explore the changes of basic nutrients, active substances and antioxidant activity of the Macadamia flowers in the bud swelling period, early flowering, and full-flowering stages, and provide the basis for its development and utilization. The changes of basic nutrients, active substance content and antioxidant activity of the Macadamia flowers at the bud swelling period, early flowering stage and full-flowering stage were systematically analyzed. The results showed that among the basic nutrients of the Macadamia flowers at three flowering stages, the water content showed a decreasing trend [the highest at the bud swelling period was (70.99±2.58)%]. Soluble protein was the highest (0.054±0.009)% in the bud swelling period. Crude fat increased first and then decreased [the highest was (2.20± 0.021)% at early flowering]. The total ash content decreased first and then increased [the highest was (3.73±0.02)% at full-flowering stage]. The early flowering stage of total sugar was the highest (1.65±0.19)%. It contained 16 abundant amino acids (7 essential amino acids and 9 non-essential amino acids), and the total amino acid content decreased with the development of flowering period. The proportion of essential amino acids and E/N value were close to the international high-quality protein standard, showing good protein nutritional value. In the Macadamia flowers at different flowering stages, the contents of five major elements in the three flowering stages showed the order of K>Ca>P>Mg>Na, highlighting the advantages of high K and low Na. The content of K at full-flowering stage was 5.2 times that of banana, and the content of Ca was 5.0 times that of milk. However, as a food development, it is necessary to pay attention to the risk of excessive As, Cr and other harmful elements. A total of 22 (the bud swelling period), 14 (early flowering stage) and 20 (full-flowering stage) volatile components were identified, mainly hexanal and d-limonene, which together constituted its unique floral characteristics.The analysis of active components showed that the content of total polyphenols decreased significantly with the prolongation of flowering period, and the bud swelling period was (18.47±2.3)mg/g. The content of total flavonoids increased first and then decreased, and the content was the highest in the early flowering stage, reaching (8.09±0.63)mg/g. The antioxidant activity evaluation showed that the DPPH and ABTS free radical scavenging rates were the highest in the bud swelling period, which were (89.96±0.61)% and (99.50±0.22)%, respectively, and the antioxidant capacity was strong. In summary, the Macadamia flowers are rich in amino acids, minerals and active substances from the bud swelling period to the full-flowering stage, and have high antioxidant capacity, which provides a scientific basis for their subsequent development and utilization.
0, 60 and 120 kg/hm2 MgO treatments (denoted by Mg0, Mg60, and Mg120, respectively) on a long-term wax gourd (Tiezhu No.2) magnesium (Mg) fertilizer gradient positioning experiment was conducted in 2022 and 2023 to investigate the physiological mechanism of Mg to improve the storage resistance of wax gourd fruits by regulating pectin metabolism by measuring indicators such as fruit hardness, weight loss rate, Mg content and morphology, pectin content and morphology, and pectin metabolic enzyme activity during fruit storage. Results showed that wax gourd yield increased by 8.5% to 16.9% after Mg fertilization, with the Mg60 treatment showing the greatest increase. Compared with the Mg0 treatment, the flesh hardness of the Mg60 treatment increased by an average of 12.9%, 11.7%, and 18.9% in the two years of 0, 30, and 60 d storage, while the Mg120 treatment showed a significant difference from the Mg0 only after 30 days of storage in 2022. Suitable Mg fertilization delayed the rise of the fruit storage weight loss rate. The fruit storage weight loss rate of Mg60 after 60 d was 34.4% and 35.1% lower than that of Mg0 and Mg120 treatment. Magnesium fertilization significantly increased fruit Mg content. Alcohol-soluble (MgEth), water-soluble (MgWat), and salt-soluble Mg (MgNaCl) were the main forms of Mg in the fruit. The content gradually increased with the prolongation of storage time. During fruit storage, the total pectin content gradually decreaseg. However, appropriate Mg fertilization (Mg60) delayed the decline in water-soluble (WSP), ion-bound (CSP), and covalently bound pectin (SSP) content, thereby maintaining the total pectin content. Suitable Mg fertilization (Mg60) inhibited the activity of polygalacturonase (PG) and β-galactosidase (β-Gal), thereby slowing down the degradation process of pectin. Concurrently, it increased pectin methylesterase (PME) activity and the content of free Mg2+ (MgEth and MgWat), enabling negatively charged pectin acid to bind with Mg2+, thereby increasing CSP and SSP. This slowed the rate of hardness decline and weight loss caused by pectin degradation during fruit storage. Comprehensively, suitable Mg (60 kg/hm2) fertilization can improve the storage resistance of wax gourd by regulating pectin metabolism, which is conducive to optimizing the Mg of wax gourd, improving the storage quality, and promoting the sustainable development of the industry.
Eotetranychus sexmaculatus Riley is an important pest mite on rubber trees, it causes damage to rubber leaves, causing localized chlorotic spots to spread to the entire leaf, resulting in severe yellowing. Severe infestations result in massive leaf drop, disrupting normal tapping operations and leading to yield losses. However, the changes in physiological and biochemical indicators of rubber tree leaves after mite damage, and the relationship with mite population density and infestation duration, remain unclear. This study aimed to reveal the effects of varying mite densities and infestation durations on physiological and biochemical traits in rubber tree leaves, and to elucidate the defense mechanisms of rubber trees, thereby providing a theoretical basis for mite monitoring and early warning and precise prevention and control of the mite. In this study, the effects of malondialdehyde (MDA), soluble sugars, soluble proteins and protective enzymes (SOD, POD, CAT) activities on the leaves of rubber trees with different infestation times were determined on the rubber potted seedlings of the same length of Thermo Scientific 7-33-97 rubber seedlings inoculated with different mite densities in the greenhouses. The two-way analysis of variance (ANOVA) was used to reveal the interaction between mite population density and infestation time. Regarding membrane lipid peroxidation damage, both mite population density and infestation duration significantly influenced MDA content, exhibiting an initial increase followed by a decrease as infestation time prolonged. MDA levels peaked at (73.91±1.89)nmol/g after 15 days of treatment with 40 mites per leaf, representing a 43.15% increase compared to the control. MDA levels began to decline to (65.09±0.29)nmol/g after 20 days. Both soluble sugar and soluble protein contents decreased with increasing mite density and duration of infestation. At a mite density of 40 mites/leaf with 20 days of continuous feeding, soluble sugar and soluble protein contents reached the lowest values at (34.42±1.43)mg/g and (17.74±0.63)mg/g, respectively, representing significant decreases of 44.20% and 45.30% compared to the control. In response to mite-induced oxidative stress, the protective enzyme activities (SOD, POD, CAT) in rubber tree leaves generally showed a significant upward trend during the early stages of mite infestation across different mite density and duration treatments. Enzyme activity peaks occurred earlier under high mite density treatments (30 mites/leaf and 40 mites/leaf). Specifically, SOD activity peaked at (13 086.92±613.39)mg/g after 5 days of 40 mites/leaf infestation, representing a 91.74% increase compared to the control. POD activity reached minor peaks at 10 days post-infestation in both 30 and 40 mites/leaf treatments (6293.13±80.75)U/(min·g) and (6655.54±51.44)U/(min·g), respectively, followed by a decline before rising again. CAT activity peaked at 10 days in the 40 mites/leaf treatment (165.77±0.41)µmoL/(min·g), representing a 62.74% increase compared to the control. Interaction analysis revealed that the interaction between mite density and damage duration significantly affected soluble sugar content (F=21.296, P<0.001), soluble protein (F=17.782, P<0.001), and significantly affected SOD (F=20.252, P<0.001), POD (F=9.821, P<0.001), and CAT (F=145.095, P<0.001) activities. Both the mite population density and the duration of damage inflicted by the E. sexmaculatus leaf mite can influence the physiological and biochemical indicators in rubber tree leaves, including malondialdehyde, soluble sugars, soluble proteins, and protective enzymes (SOD, POD, CAT). Furthermore, a significant interaction exists between mite population density and duration of damage (P<0.001). This confirms that stress intensity and duration do not act independently, but they jointly determine the physiological damage degree, nutritional status, and antioxidant defense efficiency of rubber tree leaves through a complex synergistic mechanism.
Camellia oleifera is an important woody oil crop in southern China. Due to its generally weak disease resistance, it is susceptible to various diseases, among which southern stem blight is one of the major threats to its production. This study systematically screened and analyzed the non-volatile metabolites produced by Trichoderma semiorbis FJ059 with antagonistic activity against Sclerotium rolfsii, the causal agent of southern blight in C. oleifera, and identified the potential antifungal components. The antagonistic effects of non-volatile metabolites produced in different solid-state fermentation media were compared using the growth rate method of mycelia. Results indicated that rice was the optimal substrate, yielding the highest antagonistic effect (99.61%). The solid-state fermentation products in rice media were extracted using different solvents. The ethyl acetate extract exhibited significantly higher inhibition activity than the aqueous extract. When the concentration was 500 μg/mL, the inhibition rates was 98.84% and 44.18%, respectively, indicating that the solvent selection play a vital role in the extraction of active compounds. LC-MS analysis identified several key active substances in the ethyl acetate extract, including nootkatone, caryophyllene oxide, farnesol, pyrrole-2-carboxylic acid, and trans-ferulic acid, all of which demonstrated significant antagonistic effects against S. rolfsii. Notably, the inhibition rate of 200 μg/mL nootkatone and 300 μg/mL caryophyllene oxide were both 100%, while 400 μg/mL farnesol, 400 μg/mL pyrrole-2-carboxylic acid, and 400 μg/mL trans-ferulic acid were 78.30%, 69.38% and 69.77%, respectively. The results indicated that medium-polarity or hydrophobic small molecules in the solid-state fermentation products of T. semiorbis FJ059 were potential antifungal components. The results indicated that the medium-polarity or hydrophobic small molecules detected in the ethyl acetate extract of solid-state fermented T. semiorbis FJ059 were closely associated with antifungal activity, suggesting that the ethyl acetate extract may enrich certain compounds with antifungal potential. The findings would provide new theoretical support and bioactive compound resources for the development of novel and efficient biocontrol agents against southern blight in C. oleifera.
The purpose of this study was to investigate the mechanism and efficacy of Lvnonglin ®41 compound microbial fertilizer in mitigating black pepper continuous cropping obstacles from the perspectives of soil nutrients, microbial community structure and diversity, so as to provide technical strategies for the industrial cultivation of black pepper in Hainan. Field experiments were conducted on a plot with a history of severe black pepper Fusarium wilt. Four treatments were designed: water control (CK), Lvnonglin® 41 compound microbial fertilizer (LNL41), compound microorganisms (CM), and bacterial fertilizer nutrient substrate (NS). The incidence of Fusarium wilt in the rhizosphere, plant growth and soil nutrients were measured. Using 16S rDNA sequencing technology, the differences in the occurrence of black pepper Fusarium wilt and the bacterial community structure in the rhizosphere soil under LNL41 application were explored. The results showed that compared with CK, all treatments exhibited certain effects, with the LNL41 treatment being the most effective. Soil nutrient indicators in the LNL41 and CM treatments were significantly higher than those in CK. The increases in chlorophyll content, spike length and 1000-grain weight under LNL41, CM and NS treatments reached 26.12%-67.87%, 6.20%-18.33% and 1.48%-6.44%, respectively. The incidence rates at different growth stages in the LNL41 treatment were 2.67%-15.67%, with control efficacies of 81.64%-90.06%. The Ace and Chao1 indices of rhizosphere soil bacteria increased by 12.82%-20.28% and 12.89%-18.78%, respectively, and the Shannon diversity index increased by 1.05%-3.53%, while the Simpson index showed no significant difference among treatments. At the order level, Chitinophagales, Rhizobiales and Burkholderiales were the dominant bacterial orders. At the genus level, Gaiella, P3OB 42, Lactobacillus, Pseudolabrys and Terrimonas were the dominant bacterial genera. The abundances of the common dominant genus Bacillus and Candidatus Omnitrophus were similar across treatments. Linear discriminant analysis (LEfSe) results indicated the presence of six indicator bacterial taxa in the LNL41 treatment. Ellin6067 and Tepidisphaera showed significant or highly significant positive correlations with soil pH, organic matter, available potassium, ammonium nitrogen and available phosphorus. Network analysis further revealed that the LNL41 treatment enhanced the complexity and stability of the soil bacterial co-occurrence network. Bugbase functional prediction demonstrated that the abundance of stress tolerant functional groups in the LNL41 treatment increased by 5.38 percentage points, while it decreased by 10.43 and 7.25 percentage points in the CM and NS treatments, respectively. LNL41 significantly improved the ratio of soil nutrients, thereby enhancing the structure and functional characteristics of the soil bacterial community, stimulating bacterial stress tolerance functions, promoting black pepper growth, and reducing the incidence of Fusarium wilt.
This study aimed to investigate the effects of the root exudates from Cyperus rotundus, a common weed in Guizhou tabacco fields, on the tobacco bacterial wilt pathogen Ralstonia solanacearum strain AS-1 and the biocontrol agent Bacillus velezensis strain JXF-16. Non-targeted metabolomics (LC-MS) was employed to identify the chemical composition of C. rotundus root exudates and to explore the effects of specific bioactive constituents on the two bacterial strains. Turbidimetric assays were used to measure the impact of the active compounds on bacterial growth, crystal violet staining was applied to quantify biofilm formation, and semi-solid plate culture assays were conducted to assess bacterial motility. Additionally, pot experiments were performed to evaluate the efficacy of the exogenous active compounds in controlling bacterial wilt. Results revealed that a total of 21 types of chemical compounds and 3176 active substances were detected by LC-MS. At the concentration of 50 μmol/L, myristic acid, 4-ethyloctanoic acid, ligustrazine and betaine significantly promoted the growth, biofilm formation and motility of R. solanacearum. However, at higher concentrations, the compounds exhibited inhibitory effects on bacterial growth and biofilm formation. Tetramethylpyrazine (50 μmol/L) and betaine (100 μmol/L) significantly enhanced the growth, biofilm formation and motility of B. velezensis. Conversely, lauric acid and 2-dodecylbenzenesulfonic acid at concentrations above 50 μmol/L significantly inhibited the growth, biofilm formation, and motility of both R. solanacearum and B. velezensis. Pot experiments demonstrated that lauric acid and 2-dodecylbenzenesulfonic acid at 150 μmol/L and 200 μmol/L effectively controlled bacterial wilt, with the relative control efficacies surpassing those of chemical pesticides and biocontrol agents. Notably, 2-dodecylbenzenesulfonic acid at 200 μmol/L achieved a control efficacy of 80.28%. The results would provide important theoretical insights into the role of C. rotundus root exudates within the tobacco field ecosystem and lay an applied foundation for developing novel bioactive compound-based strategies to control tobacco bacterial wilt.
With the aim of obtaining a new type of green fungicide that is low-cost, safe and highly efficient, this study investigated the antibacterial activity of Cinnamon leaf essential oil and its feasibility as a quorum sensing inhibitor (QSI), and explored its biocontrol effect on bacterial soft rot disease. In this study, the chemical composition of Cinnamon leaf essential oil was analyzed by gas chromatography-mass spectrometry (GC-MS), and the effect of Cinnamon leaf essential oil on the biological control of bacterial soft rot disease was studied, and the effect of Cinnamon leaf essential oil on inhibiting the soft rot pathogen Dickeya fangzhongdai Onc5 quorum sensing system was determined. It was indicated that a total of 16 major constituents were identified in Cinnamon essential oil and the main components were isopropyl palmitate (52.15%), cinnamaldehyde (23.02%) and isopropyl myristic acid (18.80%). Broad-spectrum antibacterial tests showed that the Cinnamon essential oil extracted from leaves had a significant inhibitory effect on five types of bacteria, including Chromobacterum violaceum ATCC31532, Pectobacterium carotovorum subsp. carotovorum, Escherichia coli ATCC25922, Serratia marcescens H30, and D. fangzhongdai Onc5. The minimum inhibitory concentration (MIC) of Cinnamon essential oil against the soft rot pathogen Onc5 was determined to be 2.5‰. Without affecting the normal growth of D. fangzhongdai Onc5, Cinnamon essential oil could weaken its flagellar motility and the release of PCWDEs, controlled the swimming and swarming of D. fangzhongdai Onc5, and effectively inhibited the soft rot pathogen. At sub-inhibitory concentrations (1/2MIC and 1/4MIC), Cinnamon essential oil was able to inhibit the activity of the plant cell wall degrading enzymes (Cel, Pel, Prt) of D. fangzhongdai Onc5, thereby limiting the ability of pathogen to invade plant cells. In order to further verify the antibacterial effect of Cinnamon essential oil, D. fangzhongdai Onc5 treated with 1/2MIC Cinnamon essential oil was inoculated on carrots, cabbage, potatoes and white radishes, and the results revealed that the pathogenicity of the bacterial liquid attenuated significantly. The research found that Cinnamon leaf essential oil exerts antibacterial effects by reducing the secretion activity of extracellular degrading enzymes and flagellar motility of D. fangzhongdai Onc5, thereby influencing its quorum sensing system. It has application prospects employed to control postharvest soft rot in fruits and vegetables as biological means, providing theoretical basis and technical support for the preservation of agricultural products and the green prevention and control of diseases.
The fruit of rambutan has a delicate and juicy taste, but it is not resistant to storage. It is prone to browning 2-3 days after harvest, which limits the market circulation of rambutan. Therefore, green, safe and convenient post-harvest preservation technology is very important for the development of the rambutan industry. The purpose of the study was to explore the effects of exogenous sodium nitroprusside (SNP) treatment on the browning of postharvest rambutan peel and its active oxygen metabolism, and to provide new ideas for the browning of postharvest rambutan. The Baoyan 7 rambutan was soaked with 200 μmol/L SNP, and the control was treated with distilled water. The weight loss rate, browning index and antioxidant enzyme activity of rambutan during storage were measured. The results showed that SNP treatment could effectively inhibit the increase of browning index of postharvest rambutan peel and maintain the peel color. Compared with the control group, the activity of reactive oxygen species (ROS) scavenging enzymes [superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX)] was significantly increased in the peel of rambutan treated with SNP, which improved the scavenging ability of reactive oxygen species radicals in the peel. The activities of polyphenol oxidase (PPO) and peroxidase (POD) were lower than those of the control, which effectively inhibited the occurrence of enzymatic browning. In addition, compared with the control group, SNP treatment can also significantly inhibit the increase of membrane lipid degradation-related enzyme activity (lipoxygenase, LOX) and maintain the structural integrity of pericarp cells. At the same time, the expression levels of browning-related genes NlWRKY23 and NlWRKY57 was significantly up-regulated. This shows that SNP treatment can enhance the antioxidant capacity of the peel of rambutan, reduce the oxidative damage of reactive oxygen species (ROS), and delay the occurrence of peel browning. The results of this study can provide theoretical basis and practical basis for the application of SNP in postharvest rambutan.
The study analyzed the soil chemical properties, nutrient contents and distribution characteristics in the litchi gardens from the major growing regions in Yunnan aimed to provide supports for nutrient and fertilization management in litchi gardens. Soil samples were collected from 22 litchi gardens in 6 major production regions. Soil pH, organic matter and multi-elements content were analyzed and used as the indicators to evaluate soil fertility via fuzzy comprehensive analysis. The results showed that soil pH was 5.62, with 22.73% of soil samples were suitable for litchi growth (pH=5.0~5.5). The cation exchange capacity (CEC) of 27.28% of soils was lower than 10.00 cmol/kg, indicating fertilizer retention ability should be improved. Organic matter content was relatively high (14.81-57.06 g/kg). Soil total N content (0.84-2.70 g/kg) was higher than medium level (>1.00 g/kg) excepting for Baoshan region. Soil alkaline hydrolyzed N (78.61-259.19 mg/kg), available P (21.14-92.48 mg/kg) and available K (35.00-642.50 mg/kg) were all higher than medium level excepting one orchard in Yongde, where the available K content (36.67 mg/kg) was at deficiency level (<50.00 mg/kg). Among the trace elements, available Ca (415.63-4900.00 mg/kg) and available S (20.43-127.89 mg/kg) were relatively abundant. Soil available Mg (3.13-512.50 mg/kg) was at moderate level, with 42.43% of samples were below the limit value (<100.00 mg/kg). Available Zn (0.51-9.68 mg/kg) and available Fe (7.18-124.82 mg/kg) were abundant. Available Mn (2.56-104.78 mg/kg) and available Cu (0.76-6.06 mg/kg) were at moderate level, with 8.60% of the samples showing available Mn lowering than 5.00 mg/kg. Available B and Mo were at sufficient level in Yingjiang at 0.88 and 0.43 mg/kg, while those in Pingbian (B: 0.44 mg/kg, Mo: 0.13 mg/kg), Yuanyang (B: 0.31 mg/kg, Mo: 0.15 mg/kg), Baoshan (Mo: 0.10 mg/kg), Yongde (B: 0.42 mg/kg, Mo: 0.10 mg/kg) and Xinping (B: 0.41 mg/kg, Mo: 0.10 mg/kg) were at deficient levels. The integrated fertility index (IFI) was 0.51-0.97, with average value at 0.79. All IFI values were above level II excepting Baoshan region at level III. The principal component analysis showed that total N, alkaline hydrolyzed N, organic matter and pH were the most important factors affecting soil fertility. The data suggested that the overall soil fertility of the studied 22 litchi gardens was above the medium level. Mg and Mo fertilizers can be improved in Baoshan, and B and Mo fertilizers can be improved in Pingbian, Yuanyang, Yongde and Xinping.
This study investigated the differences in soil physicochemical properties under three different land-use types, eucalyptus forest, orchard and rubber plantation, developed from granite-derived soils in Danzhou city, Hainan province. The results demonstrated that land use significantly influenced soil nutrient and acidity characteristics: rubber plantation soils showed significantly higher organic matter and total nitrogen content compared to other land uses, but also the most severe acidification with exchangeable aluminum content approximately 3.06 and 3.53 times higher than that in eucalyptus forests and orchards; Orchard soils were characterized by abnormal phosphorus enrichment, with available phosphorus content about 5.62 and 10.46 times higher than that in rubber plantations and eucalyptus forests, respectively, accompanied by strong base cation leaching and the lowest cation exchange capacity (CEC); Soils in Eucalyptus forests exhibited intermediate properties with relatively milder acidification. In terms of soil structure, rubber plantations were dominated by >5 mm aggregates. Combined with its most severe acidification and highest exchangeable aluminum content, this aggregate distribution pattern may indicate poor stability of large aggregates under strong acid and high aluminum toxicity environments. Although rubber plantation soils had CEC values approximately 2.47 and 3.02 times higher than those in Eucalyptus forests and orchards, respectively, the base saturation was extremely low, reflecting a significant contradiction between nutrient retention capacity and actual fertility availability. This study preliminarily suggests that the accumulation of high organic matter in rubber plantation soils may be associated with substantial litter input from rubber trees, while strong acidification and high aluminum toxicity are likely driven by continuous nitrogen cycling processes. The phosphorus enrichment in orchards primarily results from long-term excessive phosphorus fertilization. These findings provide a scientific basis for soil management and acidification control in tropical granite-derived regions under different land-use types.
Tropical mountain ecosystems are vital repositories of medicinal plant resources, and understanding the altitudinal distribution patterns is crucial for sustainable resource utilization, biodiversity conservation, and research into environmental drivers of medicinal bioactive compounds. To elucidate the altitudinal distribution patterns of the medicinal plants in Wuzhishan Mountain, Hainan, this study conducted quadrat surveys across different elevation gradients (low: 200-400 m; mid: 400-600 m; mid-high: 600-800 m; high: 800-1100 m), documenting 447 species from 260 genera and 99 families, with angiosperms comprising 93.51% of the total species. Tropical families and genera accounted for 83.35% and 86.55%, respectively (excluding cosmopolitan elements), while temperate components increased significantly with elevation. Angiosperms dominated across all elevations, whereas ferns, initially comprising only 1.80% at low elevations, increased significantly to 4.79% and 6.50% at mid-high and high elevations, emerging as a key group. The comprehensive importance value of the tree layer exhibited a bimodal distribution, with dominant species transitioning from tropical at low elevations to temperate transitional species at high elevations, reflecting a tropical-to-temperate floristic shift. The shrub layer’s importance value fluctuated downward with elevation, indicating a synergistic response to the overlying tree structure, while the herb layer shifted from shade-tolerant herbs to medicinal ferns with increasing elevation. α-diversity analysis revealed that tree layer species richness and Shannon diversity peaked at mid-high elevations, aligning with the “mid-domain effect”, while herb layer diversity peaked at mid-elevations, with Simpson dominance significantly higher than in the tree and shrub layers. β-diversity indicated that tree layer species turnover was driven by hydrothermal gradients, whereas shrub and herb layers were primarily influenced by microhabitat heterogeneity. In summary, this study systematically elucidated the vertical distribution patterns of medicinal plants in Wuzhishan Mountain, providing a theoretical foundation for the conservation and utilization of tropical mountain medicinal plant resources and insights into the environmental drivers of medicinal plant quality. Future research should focus on ecological factor analysis in the mid-high elevation (600-1100 m) fern-rich zones.
This study was aimed to explore the impact mechanism of long-term different land use patterns on the physical and chemical properties and aggregate stability of tropical soils, thereby providing a scientific foundation for enhancing soil fertility and improving soil structure in tropical regions. For this purpose, three land use types with a history of nearly 30 years were selected as the research objects, namely artificially managed rubber plantation (MR), naturally managed rubber plantations (NR), and low human-disturbed longan orchards (NL). The basic physical and chemical properties of soil, the distribution of water-stable aggregates, and the characteristics of aggregate stability in the 0‒20 cm, 20‒40 cm, and 40‒60 cm soil layers were specifically analyzed. With the increase of soil depth, the soil pH in both MR and NL patterns showed a decreasing trend. In different profile layers, the pH of MR was lower than that of NL and NR. Under each soil layer, the contents of large soil aggregates (>2 mm, 1‒2 mm) in the NR pattern were significantly higher than those in MR and NL. Conversely, the contents of small soil aggregates (<0.25 mm, 0.25‒0.5 mm) were significantly lower than those in MR and NL patterns. Both the Mean Weight Diameter (MWD) and Geometric Mean Diameter (GMD) of soil water-stable aggregates in the NR pattern were significantly higher than those in MR and NL, and the fractal dimension (D) value was significantly lower than that in MR and NL. This indicates that the soil aggregates under the natural management pattern are more stable. Analysis of variance showed that land use patterns had an extremely significant impact on soil particle size distribution and aggregate stability. Soil depth significantly influenced the distribution of aggregates in the <0.25 mm, 0.25‒0.5 mm, 0.5‒1 mm, and 1‒2 mm particle size fractions, with the intensity of the impact increasing as aggregate size decreased. The interaction effect between land use pattern and soil depth significantly affected soil aggregates (>2 mm, 1‒2 mm) and the fractal dimension (D) value. Correlation analysis revealed that the soil aggregate stability indices (content of aggregates >2 mm, MWD, GMD) were negatively correlated with soil available phosphorus and positively correlated with soil organic matter (SOM); the fractal dimension (D) was negatively correlated with the content of soil aggregates (>2 mm) and significantly positively correlated with the content of soil aggregates (<0.25 mm). In conclusion, land use pattern is the most critical factor affecting soil aggregate stability. The naturally managed rubber plantation pattern can significantly increase the content of soil aggregates, enhance soil aggregate stability, and thereby improve soil structure.
