In order to provide technical support for risk management, risk analysis and risk assessment of pests carried by citrus seedlings in China were carried out. Through consulting domestic and foreign literature, a total of 259 species of pests that may be transmitted to banana seedlings exported to China were determined, including 53 fungus, 9 bacteria,9 viruses, 11 nematodes, 167 insects, 1 mollusc, 1 weed, 8 mites (including spiders). According to the distribution of pests in China (not distributed or not widely distributed), whether it is officially controlled, and the possibility of carrying with banana seedlings, 18 potential quarantine pests were determined to be further evaluated, including 4 fungus, 7 bacteria, 4 viruses, 2 nematodes and 1 insect. The 18 potential quarantine pests were qualitatively and quantitatively analyzed one by one in terms of entry, colonization, possibility of spread, economic impact and comprehensive evaluation of multiple indicators, and 14 high-risk pests and 4 extremely high-risk pests were identified. The quarantine risk of citrus seedlings imported to China was determined to be extremely high based on the highest risk level among all quarantine pests. Finally, 18 types pests including Bisifusarium dimeru on citrus seedlings imported to China were identified, and corresponding risk management measures were proposed.

In order to enhance the antifungal activity of Streptomyces samsunensis 17-7 strain and effectively utilize its secondary metabolites, this study focused on optimizing the fermentation medium formula. Orthogonal and single factor experiments were conducted based on the original medium, with Phellinus noxious as the indicator. The optimal formulation for producing active substances from the strain was determined to include 25 g/L soy powder, 10 g/L corn meal,10 g/L glucose, 2 g/L yeast extract, 1 g/L K₂HPO₄, 0.5 g/L NaCl, and 0.5 g/L CaCO₃. Following a 500 times dilution, the relative antifungal activity of the fermentation solution increased to 51.37%, a 17.66% improvement compared to the previous optimization, demonstrating a broad spectrum of antifungal activity. The stability of the antifungal substance was evaluated in response to various conditions such as temperature, pH, protease, UV-irradiation, and storage. Results indicated that the fermentation broth of strain 17-7 exhibited high temperature resistance, a significant decrease in antifungal activity after one hour of UV irradiation, but retained its activity after long-term exposure to UV light. Furthermore, the broth demonstrated good acid-base tolerance, effective antibacterial activity in the pH range of 3-10, and resistance to trypsin and pepsin. The fermentation broth of strain 17-7 maintained its antifungal activity for 120 days at both 4 ℃ and room temperature (25 ℃). This study on the stability and storage conditions of strain 17-7’s fermentation broth offers valuable data for potential future applications of the strain as a biocontrol agent.

Camellia spp. is an important woody oil in China, which plays an important role in ensuring national grain and oil security. Previous studies showed that the self-incompatibility of Camellia spp. may be one of the important reasons for the low seed setting rate. In this study, fluorescence microscopy and morphological observation were adopted. C. hainanica Reyan 2 and Reyan 3 were used as the material, and the self-cross and hybrid combinations were Reyan 3×Reyan 3, Reyan 3×Reyan 2, respectively. Samples were collected after self-cross and cross-pollination. The difference of pollen tube growth between the two groups was compared by fluorescence microscopy. The results showed that there were different degrees of curvature at the front end of the stigmas, the number of stigmas ranged from 3 to 5, and the pistil length was slightly larger than the stamen length. The length of pistil was positively correlated with the number and length of stamen. The single flower opening lasted for 5-8 d, and the time of pollen dispersal overlapped with the time of stigma receptivity. Pollen tube fluorescence observation showed that the growth rates of autocross and outcross pollen tubes of Reyan 3 Camellia hainanica were roughly the same in the early stage, and the growth rates of both reached the peak within 12-24 h after pollination. After 36 h, the growth length of hybrid pollen tube exceeded that of autocross pollen tube until it grew into ovary. 48 h after pollination, both inbred and outbred pollen tubes could reach the base of the style, and it was observed that the outbred pollen tubes could enter the ovary, but the growth rate of the inbred pollen tubes slowed down until the growth stopped at the base of the style near the ovary. The results would provide a theoretical basis for the variety configuration and efficient cultivation of C. hainanica.

Coconut oil residue (COR) and coconut milk residue (CMR) are the two main by-products of coconut meat, which are produced during the processing of coconut oil and coconut milk, respectively. In order to explore the processing suitability of the two by-products, the nutritional and physicochemical properties of the two by-products were comprehensively analyzed. The results showed that the fat content of COR (19.37 g/100 g) was lower than that of CMR, while the nutrients such as protein (11.32 g/100 g), total dietary fiber (63.92 g/100 g), soluble dietary fiber (4.42 g/100 g), polysaccharides (25.67 mg/g), flavonoids (4.21 mg/g), total phenols (1.15 mg/g) and other active ingredients were higher than those of CMR. The hydrolyzed amino acids of COR and CMR were similar, but the content was significantly different, which was 94.955 mg/g and 56.975 mg/g, respectively. COR showed better hydration properties nificantly different, which was 94.955 mg/g and 56.975 mg/g, respectively. COR showed better hydration properties than CMR at different temperatures, but the fluidity of both was poor. COR had relatively higher thermal stability, more complete crystal structure and higher group activity than CMR. In conclusion, compared with CMR, COR has more nutrients and active ingredients, hydration properties and fluidity, and has higher thermal stability and stable crystal structure, which is an ideal raw material for low-fat, low-sugar and high-fiber food processing. The results of this study could provide theoretical guidance for the high-value utilization of coconut meat processing by-products in the food industry.

The bottom fraction of the latex from the Brazilian rubber tree (Hevea brasiliensis), specifically the biological membranes that includes lutoids and the Frey-Wyssling complex, may undergo changes in its membrane lipids and membrane proteins. The changes could affect the coagulation rate of the latex during the tapping process and the speed of blockage of the incision of the latex vessels, thereby preventing the flow of latex and reducing yield. Two types of rubber trees with rapid and normal coagulation rates of latex were selected. Liquid chromatography-mass spectrometry technology (with both positive and negative ion detection modes) was used to qualitatively and quantitatively analyze the lipids in the bottom fraction of the two types of latex, obtaining information on differential lipids. In the bottom fraction of the latex from trees with normal coagulation rates, phosphatidylethanolamine was the most abundant phospholipid subclass (accounting for about 22% of total lipids in negative ion mode and about 5.9% in positive ion mode); it was greater than phosphatidylcholine (about 12% in positive ion mode and about 4% in negative ion mode); phosphatidic acid had a high abundance (about 4% in positive ion mode and about 12% in negative ion mode), comparable to phosphatidylcholine; cardiolipin was abundant in the bottom fraction (about 6% in negative ion mode) and may be present in the Frey-Wyssling complex. In the rubber trees prone to rapid coagulation, cardiolipin in the bottom fraction significantly decreased to about 3.4% in negative ion mode. The phospholipids in the bottom fraction accounted for 31%-56%, neutral lipids 35%-54%, and glycolipids only 1%-2%. The bottom fraction contained a high abundance and quantity of non-bilayer phospholipids, namely phosphatidylethanolamine, phosphatidic acid, and cardiolipin, showing a highly dynamic nature of the latex bottom fraction. The significant downregulation of cardiolipin in the latex prone to rapid coagulation may affect the stability of the bottom fraction, thereby affecting latex coagulation, laticifer blockage, and latex flow. The discovery of high abundant non-bilayer phospholipids in bottom fraction in this study introduces a new perspective into the research of latex coagulation and laticifer blockage mechanisms.

The purpose of this study is to explore the relationship between the activity of Lvnonglin^®31 compound microbial agent (LNL31), the occurrence of blister blight and the structure of endophytic bacterial communities in tea, and to provide a theoretical basis for the rational application of microbial agents for green control of blister blight in Camellia sinensis var. assamica. The activity of LNL31 was evaluated through indoor antibacterial spectrum testing, laser confocal microscope morphology observation, pathogenic fungus spore germination inhibition rate test, and transparent circle detection enzyme activity methods. Field randomized block trials were carried out to test the disease prevention and growth promotion effects of LNL31 with different dilution ratios. Then the tea tree bud length, bud density, fresh weight and chlorophyll were respectively measured. Using 16S rDNA sequencing technology, the differences in the occurrence of the blister blight in C. sinensis var. assamica and the community structure of endophytic bacteria in leaves under LNL31 were investigated. The diluted LNL31 had obvious inhibitory effect on five pathogens, such as Exobasidium vexans EV01, Colletotrichum gloeosporioides CG02, Fusarium oxysporum FOC4, Xanthomonas axonopodis pv. citri XC01 and Escherichia coli DH5α, which caused the hyphae to break, expand and digest. The inhibition rate of LNL31 on spore germination of pathogenic fungi EV01, CG02 and FOC4 reached 89.04%-93.00%. In field randomized block trials, the application of 500-fold dilution of LNL31 had the most significant disease prevention and growth promotion effect, which was similar to the treatment of the pyraclostrobin, followed by 1000-fold dilution of LNL31. The averages of bud length, germination density, hundred bud weight and chlorophyll of the plants in the treatment of LNL31 increased by 23.14%-36.17%, 32.10%-51.38%, 27.66%-40.00% and 28.88%-36.14%, respectively, in comparison with the control. After spraying different concentrations of LNL31, the richness and uniformity of endophytic bacterial communities increased, and the results of principal coordinate analysis (PCoA) showed that there was a significant impact on bacterial communities in leaves. At the taxonomic level, Rhizobiales and Sphingomonadales were the dominant bacterial orders; Methylobacterium was the dominant bacterial genus, followed by 1174_901_12, Sphingomonas and Rhizobium. Linear discriminant analysis (LEfSe) showed that there were 9-14 indicator bacterial groups in the treatment sprayed with LNL31, compared with only 7 indicator bacterial genera in the control. Cluster analysis of species abundance showed that the unique dominant genus Baierinkia and Burkholderia in the treatment of LNL31 were similar in abundance, while Rhizobium and 1174_901_1 were similar in abundance. Correlation network analysis Bacillus is positively correlated with Eubacterium and Parabacteroide, and negatively correlated with Methylobacterium, Beijerinckia and Luteibacter. Bugbas's functional prediction showed that the abundance of aerobic bacteria, biofilm forming, gram-negative bacteria, stress-tolerant bacteria, movable elements, and facultative anaerobic bacteria treated by the composite microbial agent increased by 3.24%-14.78%, and potential pathogenic bacteria dropped by 5.70%. LNL31 showed a good effect of preventing diseases and promoting growth, and significantly changed the community structure and functional characteristics of endophytic bacteria in tea, enabling a few disease-resistant related species to grow in an advantageous way, which provided a basis for biological control of blister blight of tea.

The growth and development of pitaya are closely associated with the rhizosphere microbiome, yet there is a lack of understanding regarding the seasonal characteristics of the microorganisms during the fruit’s production cycle. This study focused on the red-fleshed pitaya in Hainan, utilizing high-throughput sequencing technology to investigate the dynamics of the rhizosphere microbial community across different seasons and its correlation with soil physicochemical factors. The results indicated that the richness and diversity of the pitaya rhizosphere microbial community were seasonally driven. There were significant differences in the Ace index, Chao1 index, Shannon index, and Simpson index among the microbial communities across seasons, particularly showing an increasing trend in autumn. A total of 6132 bacterial OTUs and 1850 fungal OTUs were obtained from 12 rhizosphere samples collected throughout the four seasons. Bacterial OTUs were classified into 43 phyla, 135 classes, 319 orders, 502 families, and 963 genera, while fungal OTUs were classified into 15 phyla, 42 classes, 103 orders, 214 families, and 423 genera. The phyla Firmicutes, Actinobacteria, and Proteobacteria showed stable and dominant relative abundances across the four seasons, making them the predominant bacterial phyla. The genus Bacillus maintained the highest relative abundance within the bacterial community, making it the dominant bacterial genus; however, its relative abundance was significantly higher in spring and winter compared to summer and autumn. The phylum Ascomycota was the dominant fungal phylum in the pitaya rhizosphere. The genus Chaetomium was the dominant fungal genus, with a notably higher relative abundance in spring compared to other seasons. Differential species analysis revealed 15 bacterial differential species and 3 fungal differential species across the four seasons. The physicochemical properties of the pitaya rhizosphere soil showed significant seasonal variation and were closely related to the rhizosphere microbial community. FAPROTAX predictions indicated that the pitaya rhizosphere bacteria primarily exhibited functions such as chemoheterotrophy, aerobic chemoheterotrophy, ureolysis, nitrate reduction, cellulolysis, nitrogen fixation, aromatic compound degradation and animal parasites or symbionts. FUNguild predictions showed that the pitaya rhizosphere fungi mainly displayed saprotrophic lifestyles and some unknown functions. In summary, this study demonstrated that the structure of the rhizosphere microbial community associated with red-fleshed pitaya in Hainan undergoes significant changes across the four seasons, with the highest diversity and richness observed in the fall. Bacillus and Chaetomium were identified as the dominant bacterial and fungal genera in the rhizosphere, respectively. The findings could provide a theoretical basis for designing cultivation improvement measures based on rhizosphere microbiota for pitaya.

Longan (Dimocarpus longan Lour.) is native to southern China and widely cultivated in the southern and southeastern regions. It is a fruit tree with high economic value. Longan seeds, as a typical recalcitrant seed, are highly sensitive to low temperature and drying, making them difficult to preserve in traditional low-temperature seed banks. After excluding the influence of ice crystals on seeds, this study conducted vitrification freezing and direct freezing ultra-low temperature storage on fresh and dry seeds, and compared the changes in physiological and biochemical indicators, contents, and starch. After dehydration and ultra-low temperature storage, longan seeds almost lost the vitality. Compared with healthy seeds, dehydration led to a significant increase in malondialdehyde content and severe damage to cell membranes. The hydrogen peroxide content showed a decreasing trend. The expression of antioxidant enzyme system increased, and the highest SOD activity was observed in longan seeds with a water content of 16% after vitrification and freezing treatment, while vitrification and freezing treatment reduced the activities of POD and CAT. Low temperature and dehydration led to an increase in the content of soluble sugars and proteins in seeds, while dehydration led to protein denaturation and a decrease in content. Observing the starch of longan seeds, it was found that after vitrification and freezing treatment, there were voids and depressions on the surface of starch particles, which were directly frozen and caused starch particle rupture. Dehydration and low temperature did not affect the molecular structure of starch, but caused some degree of damage to the internal ordered structure.

Pitaya fruit is a characteristic tropical fruit of Hainan province, mainly cultivated in the red soil of Hainan province. The exchangeable magnesium is lost throughout the year, leading to magnesium deficiency in some orchards, which affects the growth and yield of pitaya fruit. Magnesium is involved in photosynthesis and other metabolic processes. Therefore, this study took the main domestic variety of pitaya Dahong as the experimental material, using hydroponic experiments, set four magnesium concentration gradients of 0, 0.5, 2.0, 4.0 mmol/L, to determine the changes in the apparent morphology, biomass, and the activity of enzymes related to crassulacean acid metabolism in pitaya fruit. The results showed: (1) Different magnesium concentration treatments had a significant impact on the length, width, thickness, stem thickness, and fresh weight of the tender stems of pitaya fruit. When magnesium is deficient or excessive, the length, width, thickness, stem thickness, and fresh weight of the tender stems are also significantly less than those treated with 2.0 mmol/L. Magnesium deficiency can significantly reduce the length, width, thickness, stem thickness, and fresh weight of pitaya fruit. The condition of 2.0 mmol/L magnesium concentration is most suitable for plant growth; (2) The activity of PEPC first increased and then decreased with the increase of magnesium concentration. The activity of PEPC at 4 mmol/L magnesium concentration was lower than at 2.0 mmol/L but higher than at 0.5 mmol/L and 0 mmol/L treatments. after 84 days, under the condition of 2.0 mmol/L magnesium concentration, the PEPC activity in tender and old stems was the highest among other treatments, at 90.44±1.40 and 92.77±0.67 nmol/(min·g), respectively, and its initial CO₂ fixation ability was much higher than other treatments; The activity of NAD-MDH in tender stems decreased with the increase of magnesium concentration. With the extension of treatment time, the impact of magnesium concentration on NAD-MDH gradually appeared, first observed in tender stems and then gradually affected the old stems. The maximum activity of tender and old stems treated with magnesium deficiency after 84 days was (12631.82±286.04)nmol/(min·g), and (10500.16±108.34) nmol/(min·g), respectively; Under the treatment of 2.0 mmol/L magnesium concentration, the activity of NAD-ME in both tender and old stems of pitaya fruit was maintained at a high level, with an overall average of 28.41~ 65.87 nmol/min/g. (3) Magnesium deficiency had a significant effect on the enzyme activities of PEPC and NAD-MDH in tender stems. Magnesium deficiency reduced the activity of PEPC, leading to a decrease in oxaloacetic acid content, limiting the process of CO₂ conversion to malate. The accumulation of malate at night is reduced, and the raw materials for photosynthesis are insufficient during the day, thereby reducing the accumulation capacity of organic matter. Conclusion: The optimal magnesium concentration for the cultivation of domestic red-fleshed pitaya is 2.0 mmol/L. The magnesium concentration in the soil of the current pitaya planting area is lower than this value, so it is recommended to reasonably increase the application of magnesium fertilizer during the planting of pitaya.

In this study, the microbial community was analyzed by high-throughput sequencing technology in the soil of rubber plantation with different yield levels (high yield, middle yield, low yield and none yield), and relationship between microbial community and soil physical and chemical properties was also studied. A total of 2116 bacteria OTUs were obtained from all examined samples, which belonged to 17 phyla, 53 classes, 99 orders, 164 families, 305 genera and 385 species. The dominant phyla of bacterial community were Acidobacteria, Proteobacteria and Firmicutes. A total of 1622 fungal OTUs were obtained from all soil samples, which belonged to 17 phyla, 49 classes, 113 orders, 242 families, 424 genera and 644 species. The dominant phyla of fungal community were Basidiomycota, Ascomycota and Mortierellomycota. The abundance of soil bacteria community showed a downward trend was observed with the decreasing of the yield level of rubber trees, while the difference of bacterial diversity index was not significant. Ace index and Chao1 index of soil fungi showed an upward trend, and Shannon index significantly increased, while the Simpson index decreased significantly, indicating that the richness and diversity of fungal community increased with the decreasing of the yield level. Principal coordinate analysis (PCoA) showed that the community structure of soil bacteria or fungi was significantly different under the treatments. In addition, the relative abundance of dominant bacterial phyla also varied to different degrees. The characteristics of soil microbial community were closely related to soil pH and C/N. According to redundancy analysis (RDA) results, soil pH, available potassium and total nitrogen were the main soil physical and chemical factors affecting the dominant bacterial phyla, while the dominant fungal phyla were mainly affected by soil pH, available potassium and C/N.