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.

Sweet potato (Ipomoea batatas) is a globally significant food and functional crop, with its purple-fleshed varieties drawing particular attention due to the high anthocyanin content. Anthocyanins not only give the tubers distinct color but also possess antioxidant, anti-inflammatory, and disease-preventive physiological functions, making them highly valuable in the development of health foods. However, the biosynthesis of anthocyanins is regulated by a multi-level network, and the role of bHLH transcription factors in sweet potatoes has not been fully elucidated. This study focused on the sweet potato gene Tai6.33665, aiming to clarify its molecular characteristics, subcellular localization pattern, and regulatory role in anthocyanin accumulation, providing a theoretical basis for molecular breeding of high-anthocyanin sweet potato varieties. Using purple-fleshed sweet potatoe (PFSP) and white-fleshed sweet potatoe (WFSP) as materials, the study analyzed the protein structure and evolutionary relationship of Tai6.33665 through bioinformatics, detected the gene expression pattern using qRT-PCR, constructed a Tai6.33665-GFP fusion vector for transient transformation in tobacco, determined the subcellular localization using laser confocal microscopy, and analyzed the correlation between gene expression and anthocyanin content and the miRNA interaction mechanism. The results showed that the protein encoded by Tai6.33665 had a typical bHLH domain and was highly homologous to anthocyanin synthesis regulatory factors. Its expression level was significantly negatively correlated with anthocyanin accumulation (P<0.05), and it was targeted and inhibited by ib-miR52. Subcellular localization indicated that the protein was located in the endoplasmic reticulum, suggesting that it might indirectly regulate metabolism through post-translational modification or the endoplasmic reticulum pathway. This study confirmed that Tai6.33665 acted as a negative regulator of anthocyanin biosynthesis in sweet potatoes, and its function depended on subcellular localization specificity and miRNA-mediated post-transcriptional regulatory networks. This discovery not only enriches the theoretical framework of plant secondary metabolism regulation but also provides a dual-track strategy for molecular breeding by targeting knockout of Tai6.33665 or overexpression of ib-miR52 using CRISPR/Cas9, the genetic limitations of anthocyanin accumulation could be overcome, and new high-anthocyanin sweet potato varieties could be developed. Future work would focus on elucidating the interaction mechanism between the gene and MYB/WD40 proteins, as well as the regulatory pathway of its transcriptional activity by endoplasmic reticulum localization.

Phytophthora capsici is a damaging pathogen with a wide host range, causing devastating diseases such as root rot, stem rot, leaf and fruit rot in plants from diverse families like Solanaceae, Cucurbitaceae, and Legumes. The diseases pose a significant threat to the sustainability of related agricultural industries. In this study, we identified a key RXLR effector, Pc13306, from the RXLR effector repertoire of P. capsici. The coding region of Pc13306 comprised 888 nucleotides, encoding 295 amino acids, with a conserved RXLR motif residing at positions 34-37 in the N-terminal region. Utilizing a yeast secretion system, we confirmed that the signal peptide of Pc13306 exhibited robust secretory activity. Quantitative real-time PCR (qRT-PCR) analysis revealed that Pc13306 was specifically upregulated during the late stages of P. capsici infection. Through agrobacterium-mediated transient transformation of Nicotiana benthamiana Pc13306 was demonstrated to significantly enhance lesion expansion and pathogen biomass accumulation, thereby improving infection efficiency. Moreover, Pc13306 induced reactive oxygen species (ROS) bursts and hypersensitive response (HR). Further exploration into the regulatory mechanism of Pc13306 in plant immunity revealed that it activated the salicylic acid (SA) signaling pathway and autophagy processes. Notably, Pc13306 markedly upregulated the expression of core genes involved in pattern-triggered immunity (PTI), indicating its role in modulating plant immune responses. The findings would provide insights into the interaction mechanisms between P. capsici and its host, and facilitate the development of targeted disease control strategies focusing on effectors.

Alpinia oxyphylla Miq. renowned as one of the "Four Great Southern Medicinal Herbs" of China, possesses modern pharmacological activities including antioxidant, anti-inflammatory, neuroprotective, and anti-tumor effects. However, with its wild resources increasingly depleted and cultivated plants facing pressures from pests, diseases, and climate change, there is an urgent need to enhance germplasm quality and stress resistance through biotechnological approaches. This study aimed to analyze the codon usage bias in the chloroplast genome of A. oxyphylla Miq. providing a theoretical basis for its subsequent applications in genetic engineering and synthetic biology. Fifty-one high-quality protein-coding sequences from the A. oxyphylla chloroplast genome were screened based on multiple filtering criteria. Codon usage characteristics were analyzed using CodonW 1.4.2 software combined with the online platform CUSP. There existed significant A/U-ending preference. The GC content showed a decreasing gradient (GC₁=45.69%>GC₂=38.79%>GC₃=27.50%), with 90.6% of the preferred codons (RSCU>1) ending in A/U. There existed overall weak codon usage bias. The mean effective number of codons (ENC) was 46.56 (67.78% of genes had ENC>45), and the mean codon adaptation index (CAI) was 0.17. Natural selection dominated codon evolution. Neutrality plot analysis showed no significant correlation between GC₁₂ and GC₃. The actual values significantly deviated from the expected curve in the ENC-plot. The PR2-plot revealed a bias at the GC₃ position favoring A>T and C>G. Ten optimal codons were identified. This study is the first to reveal the conserved A/U-ending preference and the multifactor synergistic regulatory mechanism dominated by natural selection in the A. oxyphylla chloroplast genome. The identified optimal codons could serve as key elements for chloroplast genetic engineering in A. oxyphylla. Directional optimization of codon usage in exogenous genes (e.g., genes encoding enzymes for medicinal compound synthesis) using the codons is expected to enhance the expression efficiency, providing technical support for A. oxyphylla quality improvement and stress-resistant breeding.