The main taste components of six different coffee beans from various regions in Hainan, including Xinglong coffee beans (XL), Fushan coffee beans (FS), Qionghai coffee beans (QH), YSL coffee beans from Baisha Yushiling (YSL), MS1 coffee beans from Mushan No.1 (MS1), and MS2 coffee beans from Mushan No.2 (MS2) were studied. Differences in taste composition and component content of the roasted coffee beans from different regions were compared. Based on the chemical characterization of the beans using the fingerprinting of the main taste components, the influence of the origin on the taste characteristics components of coffee beans was investigated and the roasted beans were distinguished. The levels of eight chlorogenic acids, caffeine, trigonelline and eight organic acids in the roasted beans were measured using ultra-high performance liquid chromatography (UPLC), while the composition and content of monosaccharides in the coffee samples were determined using pulsed amperometry by ion exchange chromatography (HPAEC-PAD) and the composition and content of amino acids were determined using an automatic amino acid analyser. The results showed significant differences in the content of taste components among the roasted beans, with the highest content of caffeine and trigonelline found in MS2 beans and the lowest in MS1 beans. The highest content of amino acids was found in QH beans, while the lowest content of chlorogenic acids and monosaccharides was found in QH beans. The content of chlorogenic acids in the roasted beans was as follows: caffeoylquinic acids (CQAs)>feruloylquinic acids (FQAs)>dicaffeoylquinic acids (diCQAs). Only eight monosaccharide components were detected in the six varieties, with the highest content of galactose. Based on principal component analysis (PCA) and partial least squares discriminant analysis (PLS-DA), the six coffees beans were successfully discriminated, with high similarity between the XL coffee beans, YSL and MS2 coffees beans, indicating that the major chemical taste components can be used to distinguish coffee beans from different regions of Hainan. The results show that the fingerprinting of key taste components can effectively distinguish coffee beans from different regions. This study would provide information on the chemical composition and quality characteristics of coffee beans from different regions and provide a theoretical basis for improving coffee flavour quality, which is important for the screening and differentiation of high-quality coffee samples.

Seed germination is a key link for plants to enter the vegetative growth stage. During the germination of rice (Oryza sativa L.) seeds, the aleurone layers synthesize and secrete a series of acid hydrolases (such as α-amylase, protease) to degrade the storage substances in the endosperm and provide nutrition for the growth of rice seedlings. The degradation of storage proteins is inseparable from the role of proteasome and protease in rice seeds. In order to explore the involvement of 26S proteasome, 20S proteasome and its subunit PBA1 in the regulation of GA on the storage proteins in the aleurone layers of germinated rice seeds, the rice hybrid Teyou 128 was used as the experimental material. The activity of 26S proteasome, 20S proteasome and PBA1, the transcription level of OsPBA1 and the change of total protein content were detected by enzyme-linked immunosorbent assay and real-time fluorescence quantitative PCR. GA significantly promoted the degradation of storage proteins in aleurone cells and accelerated the germination of rice seeds. When GA synthesis was blocked, the degradation process of storage protein in aleurone layer cells was delayed, thus delaying the germination of rice seeds. Under normal culture conditions, the peak values of 26S proteasome activity and 20S proteasome activity in the aleurone layers of rice seeds appeared at 6 d and 7 d, respectively, while the OsPBA1 expression level and PBA1 activity showed peaks at 5 d and 8 d. Further studies showed that GA could induce the activity of PBA1, 20S proteasome and 26S proteasome, thereby accelerating the process of seed germination. The 26S proteasome activity inhibitor MG132 inhibited the growth of germinated rice seeds, but increased the activity of 20S proteasome and PBA1. The above studies preliminarily revealed the role of 26S proteasome in GA regulating the degradation of storage proteins in rice aleurone layers and its effect on the germination of rice seeds.

Low temperature is one of the main environmental factors affecting the growth, yield and distribution of sugarcane. It is of great significance to explore the physiological response characteristics of sugarcane under low temperature stress and screen strong cold-tolerant sugarcane parent materials for guiding sugarcane breeding and promoting the development of sugarcane industry. In this study, eight different sugarcane varieties and one sugarcane wild species (Erianthus fulvus 99-1 clone) were used as the experimental materials to study the physiological index response after low temperature stress treatment, and the cold tolerance of the nine materials was comprehensively evaluated by principal component analysis, fuzzy membership function method and cluster analysis. The contents of malondialdehyde (MDA), chlorophyll (Chl), soluble sugar (SS) and soluble protein (SP) in most materials were higher than those of CK after low temperature stress (3 ℃, 3 days). The content of proline (Pro) in all materials was higher than that of CK, while the activity of superoxide dismutase (SOD) was lower. The activities of peroxidase (POD) and catalase (CAT) in most materials were higher than those of CK. According to the comprehensive evaluation value (D) and cluster analysis, the nine materials were divided into three groups: strong cold resistance type (E. fulvus 99-1, Yacheng 89-9, ROC10), moderate cold resistance type (ROC20, Yuetang 93-159, Huangjiali, ROC16) and weak cold resistance type (Dianzhe 01-58, ROC22). The results indicate that different sugarcane varieties have different adaptability to low temperature. Strong cold-tolerant sugarcane varieties can quickly adjust themselves under adversity, reasonably increase the content of osmotic adjustment substances and the activity of antioxidant enzymes, further remove harmful substances such as reactive oxygen species (ROS) in the body, and balance cell metabolism process, so as to better adapt to low temperature environment. This study would lay a foundation for exploring the regulation mechanism of sugarcane response to low temperature stress and breeding new sugarcane varieties with strong cold tolerance.

Spontaneous plants have strong growth adaptability, can self-multiply and form a good natural landscape, which are important materials for the construction of conservation-oriented landscape. The typical-sampling method was used to investigate the spontaneous plants in 16 city parks of Haikou, so as to comprehensively understand the diversity level of spontaneous plants and provide reference for the construction of conservation-oriented gardens. The results showed that 220 spontaneous plant species belonged to 59 families and 176 genera were recorded in this research. Among them, 154 plants were native plants (accounting for 70%) and 66 plants were exotic species (accounting for 30%), meanwhile, 48 plants were invasive alien species (accounting for 22.27%). Asteraceae, Poaceae and Fabaceae, the largest families, played a major role in the quadrats with 75 species from 64 genera, accounting for 36.36% and 34.09% of the total genera and species of Spontaneous plants. Perennial herbs and annual/biennial herbs were the main life forms, accounting for 51.36% (113 species) and 44.09% (97 species), respectively. Spontaneous plants have strong ecological adaptability and high potential for landscape application. In the future construction of urban landscape, the existing spontaneous plants in the parks should be reasonably planned and utilized, increasing the proportion of native plants and constructing the spontaneous plants landscape with regional characteristics according to different environments.

Papaya is an economically important tropical fruit. Papaya ringspot virus (PRSV) is an important virus disease of papaya, often causing significant yield losses and quality deterioration. Since the introduction of the first transgenic papaya in 1998, PDR-based breeding strategies for disease resistance have been successfully applied. The contradiction between disease resistance based on sequence homology and increased virus genetic diversity became a new challenge for papaya breeding. In this study, we propose to use RNAi strategies aim at nuclear inclusion b gene (Nib) to obtain broad-spectrum resistance to PRSV papaya. With optimized embryo callus generation-Agrobatium meidated transformation-shoot regeneration, 52 shoots were obtained after resistance screening and a total of 24 transgenic positive shoots were obtained by specific PCR screening for the T₀ generation. In the T₀ generation field natural disease test, the transgenic papaya strains were significantly more resistant to disease than the non-transgenic control, with NibB5-2 having the best resistance in the field. Molecular charaterization of the insertion site of Nib5-2 was located at position 1976766 on chromosome 2 supercontig_30 by hiTAIL-PCR method. Green house inoculation test of NibB5-2 T1 generation, there was no virus accumulation and no disease symptoms, confirmed the resistance. Our resulst reveal that RNAi silcencing the Nib gene enhance the papaya virus resistance, meanwhile enriched the candidated genes for virus resistance breeding.

In order to explore the effects of nitrogen fertilizer application rate and planting density on the source-sink relationship and yield of sweet potato during ridge-sealing period, and to improve the cultivation techniques of sweet potato in Hainan, a field experiment was carried out from 2019 to 2020. The fresh-eating sweet potato variety Gaoxi14 was used as the test material, and three planting densities were set up, namely 47 600 plants/hm² (D₁), 71, 400 plants/hm² (D₂) and 142 900 plants/hm² (D₃). Four nitrogen application rates (0 kg/hm² (N₀), 60 kg/hm² (N₁), 120 kg/hm² (N₂), 180 kg/hm² (N₃) were designed in a double-factor split plot design with planting density as the main plot and nitrogen application rate as the subplot to study the effects of different planting densities and nitrogen application rates on photosynthetic characteristics, the relative chlorophyll content (SPAD), stem and leaf growth, dry matter accumulation and distribution in source and sink, tuber characteristics in ridge-sealing period, yield and its components and commodity in harvest period of Gaoxi14. Under the same planting density, the net photosynthetic rate (P_n), fresh weight of stem and leaf, number of branches, longest vine length, number of tubers per plant and single tuber weight of commercial sweet potato increased first and then decreased with the increase of nitrogen application rate, and reached the maximum at N₁ treatment. The yield of sweet potato increased first and then decreased with the increase of nitrogen application rate, and reached the maximum under N₂ treatment, which was 32.0% higher than that under N₀ treatment, but there was no significant difference between N₂ and N₁ treatments. Under the same nitrogen application rate, the dry matter distribution ratio of sweet potato roots increased first and then decreased with the increase of planting density. The D₂ treatment reached the maximum but there was no significant difference between D₂ and D₃ treatments. The root shoot ratio and yield increased significantly with the increase of planting density, and reached the maximum at D₃ treatment. The yield of D₃ was 30.9% and 24.1% higher than that of D₁ and D₂, respectively. The results of correlation analysis showed that the nitrogen application rate and planting density had significant effects on the dry matter accumulation and distribution of root tubers, while the planting density had a significant positive correlation with the yield of sweet potato at harvest stage, and the correlation coefficient was 0.704. Based on the results of this experiment, when the nitrogen application rate was 60 kg/hm² and the planting density was 142 900 plants/hm² (D₃N₁), the yield of Gaoxi 14 was the highest, reaching 30.1 t/hm², and the corresponding potato commodity rate was 94.3%, which was the best among all treatments.

The intercropping of Mallotus peltatus under the forest helps to break the bottleneck of land use. It is of great significance to apply green nanotechnology to improve the benefits of its compound planting. In order to clarify the regulatory role of nano-iron in the intercropping of M. peltatus under the coconut forest, the annual seedling of M. peltatus was taken as the research object to carry out the cultivation experiment. We investigated the comprehensive effects of five concentrations of nano-iron treatments (CK: 0 mg/L, T₁: 25 mg/L, T₂: 50 mg/L, T₃: 75 mg/L, T₄: 100 mg/L) on the leaf growth, photosynthetic and chemical characteristics of M. peltatus. After the first nano-iron treatment, the leaf length, width and dry weight of M. peltatus in T₃ treatment were significantly higher than those in CK, while the leaf number in each treatment was significantly more than that in CK. Compared with CK, the chlorophyll content of M. peltatus treated with four nano-iron concentrations increased significantly by 14.96% (T₁), 16.18% (T₂), 17.91% (T₃) and 20.58% (T₄). As the concentration of nano-iron increased, the leaf net photosynthetic rate, transpiration rate, stomatal conductance, efficiency of primary conversion of light energy of PSⅡ, actual photochemical efficiency of PS Ⅱ and electron transport rate of M. peltatus overall increased. After the second nano-iron treatment, leaf length, width, dry weight and number of M. peltatus treated with T₁, T₃ and T₄ were significantly higher than those of CK. Compared with CK, the chlorophyll content of M. peltatus in each treatment significantly increased by 10.28% (T₁), 7.53% (T₂), 11.13% (T₃) and 11.41% (T₄). With the increase of nano-iron concentration, the leaf net photosynthetic rate, transpiration rate and stomatal conductance of M. peltatus increased significantly, but decreased when the concentration reached T₃ treatment. The potential activity of PSⅡ and efficiency of primary conversion of light energy of PSⅡ of M. peltatus also decreased significantly in T₃ treatment. After two treatments, the contents of flavone, fat and ash of M. peltatus increased significantly in T₁ treatment compared with CK. The contents of fat and ash decreased with the increase of nano-iron concentration. To sum up, nano-iron has a positive regulatory effect on the growth of M. peltatus under the coconut forest, but high concentration will inhibit its photosynthesis and growth. We recommend that the appropriate concentration is 25-50 mg/L. This study could provide theoretical reference for the application of nano-iron in intercropping M. peltatus under the coconut forest.

Wampee [Clausena lansium (Lour.) Skeels] is a species of Rutaceae family and native to Southern China, which contains a large number of bioactive compounds that are beneficial to human health. However, because of the thin pericarp and soft pulp, wampee fruit is susceptible to the mechanical damage and the quality deterioration symptoms of fruit rot, pericarp browning and storage characteristic loss, and thus reducing the commercial value and edible value of harvested wampee fruit. Therefore, it is necessary to develop a safe and environmentally friendly postharvest storage technology for enhancing the storage behavior and quality, and prolonging storage time of harvested wampee fruit. Oxyresveratrol (OXY) is a naturally active product, with the efficacies of anti-browning, anti-oxidation, antibacterial, anti-inflammatory and antiviral. OXY has been studied more in the field of medicinal health care, but less in the field of food preservation. However, there are no reports on increasing the storage behavior and postharvest quality of wampee fruit by the usage of exogenous OXY. The study was aimed to study the effects of exogenous OXY treatment on the preservation of harvested wampee fruit. The fruit of wampee cv. Jixin was used as the experiment material, and the wampee fruit was treated by OXY solution with concentration of 0.2 g/L and distilled water (CK) for 30 min, separately. Then, the fruit was air-dried and packaged (50 fruits per bag), and stored at relative humidity 85% and temperature (25±1)℃ for 10 days. The changes of related indices of the storage behavior and postharvest quality in wampee fruit were observed and measured every two days. Compared to CK, OXY treatment could delay the increments of pericarp cell membrane permeability, browning degree and browning index, and maintain a higher commercially acceptable fruit rate but a lower weight loss percentage of harvested wampee fruit. Furthermore, OXY treatment might keep the higher values of L^* and hue angle, a higher total phenolics content, but the lower activities of phenolases such as peroxidase and polyphenol oxidase in pericarp of harvested wampee fruit. Moreover, OXY treatment could retain the higher contents of total soluble solids, vitamin C, titratable acidity, sucrose and total soluble sugar in pulp of harvested wampee fruit. Therefore, the treatment of exogenous OXY could effectively enhance the storage behavior, and retain the pericarp appearance quality and pulp nutritional quality, and thus prolong the storage time in harvested wampee fruit.

Phytosulfokine (PSK) is a small peptide hormone unique to higher plants, widely involved in biological processes such as plant growth and development, division and differentiation, biotic and abiotic stress. PSK receptor (PSKR) is a direct receptor for PSK and is crucial for PSK signal transduction. In the present study, HbPSKR2 was cloned from rubber tree by RT-PCR (reverse transcription-polymerase chain reaction), and its bioinformatics, gene expression pattern, interacted proteins screening and identification were also analyzed. Results showed that the open reading frame of reading frame of HbPSKR2 had a total length of 3159 bp and encoded 1052 amino acids with molecular weight 114.84 kDa and theoretical isoelectric point 6.34. Domain analysis showed that HbPSKR2 was a typical trans-membrane protein. The first 640 amino acids were the antenna structures composed of leucine rich repeat (LRR), the 692 to 714 amino acids were transmembrane domains, and the 765 to 1052 amino acids were kinase domains. Multiple comparisons were conducted on the membrane kinase domain of HbPSKR2 and the membrane kinase domain of PSKR homologous proteins in Arabidopsis and rice. The results showed the existence of conserved sites such as ATP binding site, CaM binding site, Activation segment, GC Centre. Expression pattern analysis showed that HbPSKR2 was highly expressed in the cambium region of rubber tree. The expression level of HbPSKR2 was significantly increased at the early stage of coronatine (COR) treatment. Twelve candidate proteins interacted with HbPSKR2 were screened by yeast two hybrid technology, and the interaction between two protein kinases (HbPBL8 and HbPIX13) and HbPSKR2 was further verified by luciferase complementary imaging. The strong fluorescence signal was observed by co-transformation HbPSKR2-nLUC/HbPBL8-cLUC and HbPSKR2-nLUC/HbPIX13-cLUC into tobacco, suggesting the interaction between HbPSKR2-HbPBL8 and HbPSKR2- HbPIX13 in vivo. The cloning of HbPSKR2 and identification of HbPSKR2 interacted protein would provide new insights into the molecular mechanism of laticifer differentiation in rubber tree.

Banana classification is a difficult problem, using morphological features to classify is unable to meet the needs. Molecular marker technology has been gradually applied to population identification and classification, genetic relationship analysis and genetic diversity research of banana varieties (lines). In this paper, SRAP molecular marker technology was used to analyze the genetic relationship of 89 banana germplasm resources. Using 10 pairs of positive and negative primers to form 100 pairs of primer combinations, and 13 pairs of SRAP primers with easy identification, clear band type and high polymorphism were screened out. 170 identifiable bands were amplified by the 13 pairs of primers, with an average of 13.08 bands per pair of primers, of which 140 bands showed polymorphism, with a polymorphism ratio of 79.00%. The similarity coefficient of 89 banana germplasm resources varied from 0.241 to 1.000, and the genetic diversity was very rich. The similarity coefficient of the same type of wild banana from the same place or different places was high. When the similarity coefficient was 0.49, the 89 banana resources could be divided into six groups. The first major category were AAA group Xiangyajiao, AA group Gongjiao, AAB group Longyajiao and AA group wild banana (AAA, AA, AAB). The second major category were ABB group Fenjiao, ABB group Fendajiao and BB group wild banana (ABB, BB). The third major category were Dajiao and a banana wild relative Musa itinerans. M coccinea, Musella lasiocarpa, Heliconia belonged respectively to the fourth, fifth and sixth category. The results are basically consistent with the current classical classification conclusion. Only some banana germplasm have different classification status, indicating that it is feasible to use SRAP markers to classify banana germplasm resources. At the same time, the cultivated Xiangya banana, Gongya banana and Longya banana have the same ancestry, and are close to the wild banana of AA genotype, while the wild banana of BB genotype is close to the pink banana, the pink banana and the wild banana of BB genotype, and the banana germplasm resources of different genomes are gathered together, which showing that the origin of banana germplasm resources affects the genetic relationship of offspring, and a single classification method cannot completely distinguish the banana germplasm resources. In addition, the genetic relationship between plantain and plantain is relatively close, but it is impossible to distinguish whether plantain contains A and B genomes, so the genotype and genetic background of plantain need further study.