Frequent pre-harvest fruit abscission occurs during the development of longan fruits due to insufficient carbohydrate supply. The metabolism of carbohydrates is closely related to energy metabolism, and changes in energy charge related respiration and carbohydrate consumption, which are important indicators for measuring fruit physiological functions. In order to reveal the relationship between abnormal abscission and energy charge of longan fruits, this study used the fruits of the late stage of development (80 days after flowering) of “Chu Liang” longan as the materials, and used ear girdling plus defoliation treatment to block carbohydrate supply and artificially create hunger stress, which can lead to complete fruit abscission within 5 days. During this process, this study analyzed the changes in ATP, ADP, and AMP contents and energy charge levels in different tissues during fruit abscission. The results showed that the energy charge values of different tissues in the fruit were as follows: seeds>fruit skin>fruit flesh, and with the intensification of starvation stress, during the fruit abscission process, ATP significantly decreased and AMP significantly increased throughout the experiment. The energy charge values of different tissues showed a downward trend, but the decrease in seed energy charge value was the smallest, and the seed was the organ with the most stable energy charge. The results indicated that starvation stress could lead to a decrease in fruit energy levels, but the magnitude of energy changes varied among different tissues, seeds could maintain relatively stable energy charge levels, suggesting that under starvation stress, fruit resources prioritized the supply of seeds, thereby maintaining the energy state.

Photosynthesis plays a crucial role in the growth and development of plants, and the light response curve can describe the relationship between photosynthetic rate and light intensity under different light conditions. As a thermocrop plant, clarifying the photosynthetic characteristics of Noni is crucial for understanding its growth and development process, while there are relatively few reports on the photosynthetic aspects of Noni. In order to study the photosynthesis of Noni and its environmental adaptation, this study took Noni with four shade treatments (CK, T₁, T₂, T₃) as the research object, and measured the daily change of light intensity, daily change of net photosynthesis and light response curve by LI-6400 portable photosynthesizer, and used four commonly used light response models to fit, and then screened the optimal model to obtain the corresponding photosynthetic characteristic parameters. The daily change of light intensity showed a single-peak parabolic trend, and the daily light intensity reached the maximum at 12∶00 noon, while the daily change of net photosynthesis of Noni showed an inverted U-shaped change, with a rapid increase from 6∶00 to 10∶00, and a slow decline from 10∶00 to 16∶00, and a rapid decline at 16∶00. The daily changes of the two existed some synchronous and non-synchronous changes. The net photosynthetic rate (P_n) and light intensity (I) both showed obvious decreasing trends with the increase of shade between different treatments. The modified model of the right-angle hyperbola (MRHM) fit most effectively for the light response curve of Noni. With the exception of 90% shade, both the root mean square error (RMSE) and mean absolute error (MAE) were lower than those of the other three models, ranging from 0.06 to 0.12 and 0.05 to 0.09, respectively. With the increase of shade, the photosynthetic apparent quantum efficiency (AQE), maximum net photosynthetic rate (P_nmax), light saturation point (LSP) and dark respiration rate (R_d) of Noni gradually decreased, while the light compensation point (LCP) gradually increased, indicating that under the induction of low light, the photosynthetic efficiency of Noni gradually decreased, and the photosynthetic efficiency of Noni gradually decreased when over-shaded. This indicates that the photosynthetic efficiency of noni decreases gradually under low light induction, and even decreases dramatically under excessive shade, and its high photosynthetic efficiency can only be activated under strong light stimulation. This study reveals the photosynthetic characteristics of Noni and its response strategy to different shade, which would provide a theoretical basis for the deep understanding of Noni ecological adaptation, and also provide a reference for the production of Noni understory planting or shade measures.

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.

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 order to investigate the edible quality of different provenances of areca nuts, this study was carried out to determine the contents of cellulose, hemicellulose, lignin, protopectin and arecoline, and to analyze the textural structure of hardness, chewiness, viscosity, springiness and cohesion of areca nut from different varieties planted in Hainan. The results showed that there were significant differences between different provenances of areca nuts in terms of fruit shape, hemicellulose, chewiness, viscosity, cohesion and arecoline content. HN-TY showed good quality characteristics of soft fiber and high viscosity. HN-YG had the least hardness and high elasticity. HN-TY and HN-CG had high arecoline contents of 5910.61 and 7121.70 μg/g, respectively. In addition, among all the traits, arecoline content varied most frequently among betel nuts of different varieties and the coefficients of variation were large. Protopectin content was the most unstable, with the coefficients of variation ranging from 27.78% to 74.88%. The coefficients of variation for each trait of the TW were generally large, resulting in a rich genetic diversity. The present study would provide information on the important quality of different provenances of areca nuts available in Hainan province, while the determination of the coefficients of variation of thirteen trait indexes of areca nuts in six groups provide a basis for parental selection in areca nut improvement.

Cassava, commonly known as the “underground granary”, serves as the food staple for more than one billion people globally. Additionally, it is a prevalent and advantageous crop in southern China. Recently, the food security situation has intensified, leading to an increased emphasis on the utilization of cassava in China. Therefore, the breeding of new sweet cassava variety holds immense importance. In this study, using a self-crossing segregating populations and SNAP molecular marker assisted technology, a new sweet cassava variety, Gui 11 was bred. This variety exhibits a compact plant shape, with light yellow fleshy roots. The hydrogen cyanide content in its fresh tuberous root is 12.30 mg/kg, and it yield is 43.35 t/hm², presenting 24.64% higher than the current main sweet cassava variety 'South China 9'. Additionally, the fresh tuberous root of Gui 11 contains 38.40% dry matter, 28.20% starch, 4.71% soluble sugar, and 1.80% crude fiber, and it displays moderate resistance to Tetranychus cinnabarinus. The successful breeding of Gui 11 exemplifies the effective utilization of molecular marker technology to assist in the selection of new cassava varieties through self-crossing segregating populations. This advancement offers technical and variety support for promoting the transformation and enhancement of the cassava industry.

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.

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.

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.