Anthracnose caused by Colletotrichum gloeosporioides occurs extensively during the post-harvest storage of papaya (Carica papaya L.), significantly affecting fruit quality and yield. In this study, the excellent antagonistic bacteria J-11 agaist C. gloeosporioides were screened from the rhizosphere soil of papaya, and the antagonistic characteristics and biological control ability were explored. The size of biocontrol bacterium J-11 was about 1.5 μm×3.3 μm (growing for 3 d), Gram-positive (G⁺), rod-shaped or oval, common single arrangement, and its morphological characteristics were consistent with Bacillus velezensis. The sequences of 16S rRNA, gyrA and gyrB genes of strain J-11 were 99.28%, 97.57% and 98.79% consistent with those of B. velezensis model strain OOT-47, respectively. Phylogenetic tree analysis showed that the tested strain J-11 and Bacillus velezensis LB4 were clustered into one branch. According to the results of morphological, molecular biological and physicochemical analysis, it was confirmed that the microbial antagonistic pathogen of papaya C. gloeosporioides in Zhanjiang area of Guangdong was B. velezensis. Strain J-11 demonstrated a broad-spectrum antifungal ability, inhibiting the growth of three pathogenic fungi of C. gloeosporioides, C. siamense and Botryosphaeria dothidea, with antagonism indices of 0.48, 0.41 and 0.40, respectively. The control testing showed that the inhibition rate of strain J-11 against the C. gloeosporioides on papaya leaves was 89.96%, and the inhibition rate of strain J-11 against the C. gloeosporioides on papaya fruits in vitro was 84.92%. Strain J-11 screened in this study has a certain control effect on papaya anthracnose, which could provide a theoretical basis for in-depth study of the antibacterial mechanism of plant biocontrol bacteria and will lay a foundation for its development and utilization.

The fruits of Qiongdong No. 9 Camellia oleifera at five developmental stages were taken as the experimental materials to ascertain the basic characteristics of the growth and development in Hainan and the changes in the content of antioxidant active substances. The morphological characteristics were observed, the crude fat and six main active ingredient contents of the seeds at different developmental stages were measured, and four antioxidant activity indicators of the seeds at different developmental stages were detected. The results demonstrated that the growth changes of each part of the fruit generally followed a logistic curve, presenting a slow increase in the initial stage, a rapid growth in the middle stage, and eventual stabilization. During the whole growth period, changes in crude fat content continued to accumulate, with S₃-S₅ being the period of rapid oil accumulation; the changing trends of the contents of flavonoids, total polysaccharides, vitamin E, ABTS radical scavenging ability and total antioxidant activity (FRAP) in seed kernels were consistent, experiencing a process of rapid decrease-significant increase-slow decrease. The content of carotenoids and the ability to scavenge hydroxyl radicals showed a significant increasing trend at all stages. The content of total phenols, total saponins, and total antioxidant activity (DPPH) showed a gradually decreasing trend. Through Pearson correlation analysis, the content of six active ingredients was significantly correlated with four antioxidant capacity indicators to varying degrees, and each ingredient had a different degree of response to different antioxidant capacities. S₁–S₃ were the rapid swelling stages of the fruit, accompanied by significant fluctuations in the content of active ingredients. S₃–S₄ were the key stages of substance transformation, and S₄–S₅ were the steady-state accumulation stages of contents; In the early stages of fruit development (S₁–S₃), water-soluble antioxidant components such as phenols, saponins, and polysaccharides dominated, while in the middle and late stages (S₃–S₅), they shifted towards lipid soluble components (carotenoids) and lipids. This competitive process was an important reason for the decrease in the content of the main active components. This research revealed the growth and development characteristics of C. oleifera fruits in tropical areas, which would have theoretical reference value for formulating corresponding cultivation and management measures for quality breeding purposes.

The MYB family constitutes one of the largest transcription factor families in plants, involving in plant growth and development, signal transduction, and secondary metabolism. Based on our previous 2+3 transcriptome data of Ocimum basilicum var. pilosum, we systematically identified the O. basilicum var. pilosum MYB (ObMYB) family through bioinformatics approaches and explored members associated with essential oil accumulation. Firstly, ObMYB members were screened by homologous alignment of MYB conserved domains, and then their complete open reading frames were predicted and the basic physicochemical properties of these encoded proteins were analyzed. Phylogenetic relationship was reconstructed by neighbor-joining method of MEGA 7.0, while conserved motifs and domains were annotated using MEME and Batch CD-Search. Subsequently, incorporating the previous miRNA data of O. basilicum var. pilosum, the targeted miRNA complementing the ObMYB were predicted by TargetFinder. Lastly, differential expression analysis and visualization analysis of heat maps were conducted by TBtools. Based on the essential oil data from different developmental stages of stems and leaves, the correlation analysis between differential gene expression levels and essential oil content was conducted using SPSS 25 to identify the potential ObMYB members involving in the accumulation of essential oil. The protein-protein interaction (PPI) network was constructed by STRING database for analyzing potential metabolic pathways involved. Research results revealed that a total of 77 ObMYB members were characterized, named as ObMYB-1 to ObMYB-77. Phylogenetic analysis divided them into eight subfamilies (classⅠ-Ⅷ), each comprising 6–14 members. These ObMYB proteins exhibited hydrophilic properties and structural stability, average isoelectric point=7.11 and average hydrophobicity=–0.69. Five miRNAs were found to target and regulate four ObMYB genes. Among these 43 differentially expressed ObMYB genes, ObMYB-4, -9, -27, -34, -42, -46 and -69 displayed strong correlations with essential oil accumulation. Moreover, PPI network analysis indicated the potential involvement of ObMYB-4, -9, -34, -36, -46 and -69 in flavonoid biosynthesis and secondary metabolite regulation. This study systematically identified the ObMYB family members and analyzed their relationship with essential oil accumulation, revealing multiple ObMYB genes significantly associated with the synthesis and accumulation of essential oils. These findings provide a significant theoretical basis for an in-depth understanding of the metabolic regulation mechanisms of O. basilicum var. pilosum essential oil, and to offer new targets and insights for research on plant secondary metabolism and the improvement of aromatic plant quality.

Tropical agriculture is critical to global food security and rural revitalization. However, its modernization is constrained by complex terrain, climatic variability and frequent disasters. Remote sensing, with its capacity for large-scale, real-time information acquisition, has emerged as a key enabler for smart and precision agriculture in tropical regions. This study established a framework for remote sensing research in China's tropical agriculture, proposing an integrated “space-air-ground” observation strategy and explaining the resolution-to-application matching mechanism, in which low-, medium-, and high-resolution observations are respectively suited for regional resource surveys, farmland growth monitoring, and field-scale phenotypic diagnostics. It reviewed progress in natural resource surveys, crop monitoring yield estimation, disaster assessment and ecological evaluation, analyzed challenges such as insufficient ground-truth data, limited model transferability, poor regional adaptability and low transformation efficiency; and proposes key innovation paths including coordinated sensing, multi-modal data fusion, intelligent modeling and digital twin-based forecasting. Finally, it outlined future directions focusing on system integration, intelligent perception, and global collaboration. The findings would provide theoretical and technical support for enhancing remote sensing applications in tropical agriculture.

Areca palm velarivirus 1 (APV1) is identified as a causative agent of yellow leaf disease (YLD), which emerges as a prominent threat to betel palm plantation. Developing methods for rapid detection of APV1 is necessary for preventing and controlling YLD in betel palm cultivation. In this work, APV1 virions were extracted from APV1-infected Nicotiana benthamiana by using polyethylene glycol (PEG) precipitation, ultracentrifugation, sucrose density gradient centrifugation, and affinity magnetic beads. The purified APV1 virions were identified by transmission electron microscopy (TEM), SDS-PAGE and Western blotting. The purified APV1 virions were used to immunize BALB/c mice to produce polyclonal antiserum for detection of APV1. APV1 virions were precipitated from N. benthamiana homogenates by applying 5% PEG6000 and 0.6% NaCl. After resuspension and ultracentrifugation with 55% sucrose cushion, APV1 virions were distributed in the lower part of the sucrose layer or precipitated at the bottom of the centrifuge tube. APV1 was purified by 30%, 40%, 50%, 60% and 70% discontinuous sucrose density gradient centrifugation at 140 000×g for 2 h, and the results showed that APV1 was enriched in 60% and 70% sucrose layers. Affinity magnetic beads could efficiently purify APV1 virions. The purified virions were elongated, about 650–2200 nm in length and 10–13 nm in diameter. BALB/c mice were immunized with the extracted APV1 virions to obtain antiserum with high specificity for APV1 and titer of 1∶25 600. The results would provide a new idea for the separation and purification of APV1, and an important technical support for rapid detection of APV1.

The yield of tropical crops is highly sensitive to climate conditions, and accurately modeling the meteorological-driven mechanisms is crucial for improving tropical agricultural productivity and climate adaptability. This study systematically compared the prediction performance of six machine learning models, including LGBM, RF, XGBoost, AdaBoost, SVM and MLR based on natural rubber, mango, pineapple and banana in Hainan. The SHAP method was used to quantify the contribution and non-linear response characteristics of meteorological factors. The LGBM model demonstrated the best prediction performance, with an average R² of 0.945 for the test set (the R² of rubber, mango, pineapple and banana were 0.942, 0.902, 0.954 and 0.983, respectively), and average RMSE and MAE of 1.436 t/hm² and 1.150 t/hm², significantly outperforming the other models (the R² of RF, XGBoost, AdaBoost, SVM, MLR were 0.773, 0.563, 0.589, 0.368 and 0.508, respectively). The meteorological-driven mechanisms exhibited significant crop-specific differences. Rubber yield was mainly driven by solar radiation (the contribution was 14.7%) and temperature factors (the contribution of monthly minimum temperature and monthly maximum temperature were 14.4% and 11.7%, respectively). Mango yield was highly sensitive to monthly maximum temperature (the contribution was 19.0%) and vapor pressure deficit (the contribution was 18.5%). Pineapple and banana yield were dominated by soil moisture (the contribution was 18.9%) and relative humidity (the contribution was 23.6%), respectively. Based on the findings, differentiated agronomic management recommendations for each crop type were proposed. This study demonstrates that machine learning, combined with explainability methods, can effectively elucidate the climate response mechanisms of tropical crops, providing theoretical support for regional agricultural precision management.

The study was aimed to develop organic fertilizers replacing chemical fertilizers and reveal the effect mechanism of fertilization on plant health, endophytic bacterial community structures in tomato roots. Five fertilization treatments were set up, no fertilization (CK), application with chemical fertilizer (T₁), peanut cake fertilizer (T₂), soybean cake fertilizer (T₃) and tea cake fertilizer (T₄) at the identical nitrogen level. Meanwhile, based on high-throughput sequencing technology, the endophytic bacterial community structure in tomato roots was analyzed. The numbers of endophytic bacterial communities in tomato roots at different taxonomic categories were all improved over CK. Meanwhile, except T₄ treatment, the diversity and richness of endophytic bacteria community in tomato roots under T₂ and T₃ were all higher than those of T₁. At the phylum or genus level, the endophytic bacterial composition and the percentage in tomato roots were all altered by different fertilizer treatments. Among them, not only the numbers of dominant endophytic bacterial were improved, but also the endophytic bacterial community structures were reshaped. Particularly, some beneficial bacterial genera, such as Rhizobium, Bacillus, Microbacterium, Castellaniella, with the function of growth promotion, plant resistance and quality improvement enriched in tomato roots under T₂ treatment. Compared with CK, the diversity and richness of endophytic bacterial community in tomato roots were improved, and the endophytic bacterial composition in tomato roots could be reshaped by different fertilization. The highest diversity and richness of endophytic bacterial communities could be found in tomato roots under T₂ treatment, followed by T₃ treatment. The beneficial endophytic bacterial genera, such as Rhizobium, Bacillus, Microbacterium and Castellaniella enriched in tomato roots under T₂ treatment only. It indicated that the effect of peanut cake fertilizer on plant health was better than those of chemical fertilizer, soybean and tea cake fertilizers under the identical nitrogen levels.

Cryopreservation can reduce the risk of genetic variation in the long-term subculture of rubber tree anther callus tissue, and is an effective method for long-term preservation of callus tissues. To evaluate the effects of dehydration duration on physiological parameters during cryopreservation, rubber tree anther calli were treated with plant vitrification solution PVS2 for 0, 10, 20 and 40 min and then cryopreserved for 24 h in this study. Physiological parameters related to stress resistance were analyzed, including soluble protein content, malondialdehyde (MDA) content, and activities of catalase (CAT), superoxide dismutase (SOD), and peroxidase (POD) during cryopreservation. Dehydration duration had a significant effect on soluble protein content, MDA content, SOD and POD activities in callus tissues after cryopreservation, while showing no significant impact on CAT activity. All physiological parameters (except MDA) exhibited higher values after cryopreservation compared to pre-preservation levels across all dehydration durations. After 40 min of dehydration and cryopreservation, the soluble protein content, CAT, SOD and POD activities of anther callus reached the maximum value, which was 129.63 μg/mL, 627.30 U/g, 290.38 U/g and 25 643.33 U/g, with the lowest MDA content of 41.31 nmol/g. The findings indicate that dehydration for 40 min significantly enhances water retention capacity and antioxidant level in cryopreserved callus cells. Post-thawing viability tests revealed that 40 min dehydrated callus maintained over 70% survival rate and could induce fragile embryogenic callus formation with an average induction rate of 13.33%. This study establishes a physiological foundation for the regeneration of cryopreserved rubber tree anther callus.

Cucumber green mottle mosaic virus (CGMMV) is one of the important plant viruses that harm melon crops, and its movement protein (MP) plays a key role in virus transmission and pathogenicity. This study cloned the MP gene of CGMMV through RT-PCR, constructed the prokaryotic expression vector pET-32a-MP, and successfully induced the expression of a recombinant MP fusion protein with a molecular weight of approximately 48 kDa in Escherichia coli BL21 (DE3). Purification of high purity protein (purity degree≥80%) using nickel column affinity chromatography was used to prepare polyclonal antibodies against the New Southwest White Rabbit. Western blot and ELISA analysis showed that the titer of the anti serum reached 409 600, and it could specifically recognize the MP protein in CGMMV infected leaves, without cross reactivity with other viruses such as Tobacco mosaic virus (TMV) and Watermelon mosaic virus (WMV). The study would provide important tools for rapid virus detection, immunohistochemistry, and protein function research, which is of great significance for ensuring the safe production of melon crops.

Diploid (2n) and tetraploid (4n) seedlings were used in this study to access the optimal light quality for the growth of Anthurium andraeanum Pink Champion seedlings. Different LED light configurations with varying ratios of red light (R) and blue light (B) served as the light source, while fluorescent daylight lamps were used as the control (CK). Seven types of light qualities were set up: CK, R, B, R5∶B5, R6∶B4, R7∶B3, and R8∶B2. The study evaluated how different light qualities affected the growth of A. andraeanum seedlings, as well as the contents of soluble sugar (SS), soluble protein (SP), hydrogen peroxide (H₂O₂), and malondialdehyde (MDA) in the leaves. Additionally, the activity of superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD) was measured. The results indicated that, compared with the control, red light (R) reduced leaf width, leaf area, and biomass of the two types of seedlings, and increased the POD activity in both seedlings, also the CAT activity and MDA content in the 2n seedlings. Blue light (B) significantly decreased the biomass, SS, and H₂O₂ content of the 4n seedlings, and increased the CAT and POD activity in both 2n and 4n seedlings, and the SOD activity in the leaves of the 2n seedlings. The combination of red and blue light qualities had the ability to mitigate the growth reduction or MDA increase caused by the individual light types. The combined red and blue light treatment increased the number of leaves, leaf area, leaf width, root length, biomass, SP content, and SOD and CAT activity in both types of seedlings. As the proportion of red light increased, biomass and protective enzyme activity initially rose and then declined, peaking under the R7∶B3 treatment. Conversely, H₂O₂ and MDA content exhibited an inverse trend. In conclusion, the appropriate ratio of combined red and blue light significantly promotes the morphogenesis and biomass accumulation of A. andraeanum seedlings, and enhances the antioxidant capacity. After a comprehensive evaluation using membership functions, R7∶B3 was determined to be the most effective among the seven light qualities, making it the optimal choice for the growth of A. andraeanum seedlings.