The study of methane (CH₄) emission flux from paddy fields is an important part and hot topic in the current study of carbon cycle in terrestrial ecosystems. The multi-time scale characteristics of CH₄ emission flux and its influencing factors [gross primary productivity (GPP), latent heat flux (LE), air temperature (TA), soil temperature (TS)] in paddy fields were analyzed based on wavelet analysis and eddy covariance flux observation data. The CH₄ emission flux and its influencing factors of paddy field ecosystems had obvious seasonal variation characteristics. The CH₄ emission flux from paddy fields in the rice growing season showed obvious single-peak diurnal variation characteristics, while the CH₄ emission flux from paddy fields in the non-rice growing season was low, and the diurnal variation characteristics were not obvious. GPP, LE, TA and TS showed obvious single-peak diurnal variation patterns. Based on continuous wavelet transform and wavelet variance curve analysis, CH₄ flux, GPP, LE, TA and TS had an obvious 1-day cycle during the rice growing season (July—November), while GPP, LE, TA and TS also had a half-day cycle, and TA and TS also had a long-term cycle of 4 days. From the cross wavelet transform and wavelet coherence spectrum analysis, the resonance period between CH₄ flux and GPP, LE, TA and TS was about 1 day. There was a significant resonance relationship in this frequency domain, and oscillation cohesion and coherence were the strongest. However, in the high-frequency band area, there was also a secondary resonance period of about 0.5 days between CH₄ flux and GPP, LE, TA and TS. In addition, in other frequency bands, the resonance energy of CH₄ flux and GPP, LE, TA and TS was low, but in the resonance period of 4 days and 7-10 days, CH₄ flux had good coherence with TA and TS from mid-August to mid-October. This study analyzed the multi-time scale characteristics of CH₄ flux and its influencing factors from paddy fields and would provide a scientific reference for studying the quantitative relationship between CH₄ flux and its driving factors at different time scales.

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.

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 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.

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.

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.

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.

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.

Chalcone synthase (CHS) is the first limiting enzyme in flavonoid synthesis pathway and plays an important role in flower color formation, growth and development, and abiotic stress. In order to clarify the characteristics of cassava MeCHS gene family and its expression in cassava postharvest physiological deterioration (PPD), the MeCHS gene family was analyzed using bioinformatics, including physicochemical property and subcellular location. qRT-PCR was carried out to detect the expression levels of MeCHS genes in different varieties, different tissues and PPD process. The genes with significant relative expression were selected for cloning and subcellular localization verification. A total of 5 MeCHS gene members were identified in the cassava genome. The secondary structure analysis showed that the MeCHS gene family was mainly composed of α-helices and random coils. Tissue specific expression indicated that the expression levels of MeCHS genes were higher in stems. The major expressed MeCHS genes in cassava were MeCHS1, MeCHS2 and MeCHS3; and the expression levels of these three genes were gradually increase with PPD. MeCHS1, MeCHS2 and MeCHS3 were successfully cloned; and fluorescence transient expression showed that MeCHS1, MeCHS2 and MeCHS3 were localized in the cytoplasm, which was consistent with the predicted results. This study will provide a theoretical basis for further revealing the function of MeCHS gene family and improving the PPD tolerance of cassava.

The study of crop spatial pattern has important theoretical and practical significance, and has become the frontier and hotspot of geography and ecology. This paper systematically summarized the current progress of allocation method, driving force analysis and simulation of crop spatial pattern. And in this paper, a mind map of research work is presented based on the discussion of the deficiencies and the trends in the study of crop spatial pattern. It is showed that the methods of statistical investigation, remote sensing and spatial model have their advantages and disadvantages in the work of crop spatial information allocation. And it is difficult to fully understand the process of crop spatial pattern change only from the perspective of natural driving force or socio-economic driving force in the work of driving force analysis and simulation of crop spatial pattern. It is suggested that the spatial information comprehensive allocation technology based on spatial model, the multi-factor and multi-scale driving force analysis method combining natural and socio-economic factors, and the simulation model coupling geographical model and socio-economic model will be the important development directions in the field of crop spatial pattern research.