Areca palm is an important tropical economic crop in Hainan Province. Areca palm yellow leaf disease (YLD) caused by phytoplasma infection is a devastating disease in the production of areca in China. In order to establish an accurate and efficient detection method for areca palm yellow leaf phytoplasma, this study designed and synthesized specific primers AMf/AMr and AM-Prode based on the 16S rDNA gene of areca palm yellow leaf phytoplasma. The method was used to test the accuracy, sensitivity, specificity and repeatability, and to detect phytoplasma diseases in other plants. The method could accurately detect the positive samples, and the healthy samples had no amplification curve. In the sensitivity test, the method could detect the sample concentration level of 1.16×10¹ copies/μL, and the standard curve equation was y=–3.4185x+43.624, the amplification efficiency was 96.12%, and the correlation coefficient R²=0.9833. In the specificity test, the method had good specificity for the detection of YLD, and the genomes of areca, other disease pathogens and the endophytes did not interfere with the method. In the repeatability test, the method had good repeatability for the detection of YLD. The detection method could be used to detect 8 phytoplasma diseases such as chinaberry yellow leaf disease, ‘Pericampylus glaucus’ witches' broom disease and pepper yellow leaf disease and the detection of phytoplasma has certain universality. The establishment of detection method is conducive to providing reliable technical means for the accurate diagnosis of YLD, pathogen monitoring and vector insect detection.

Sporisorium scitamineum, the pathogen of destructive disease smut, usually causes abnormal growth of meristematic tissue and forms a “black whip” in meristem tissues. In some cases, it induces formation of flowering structures in some sugarcane cultivars (genotypes), but the exact mechanism remains unclear. In order to explore flowering related genes and the expression patterns in sugarcane in response to infection by S. scitamineum, the healthy and S. scitamineum infected ‘guitang42’ sugarcane cultivar samples were analyzed by transcriptome sequencing. A total of 3276 differentially expressed genes (DEGs) were identified, of which 1677 genes were up-regulated (P<0.05) and 1599 genes down-regulated (P<0.05). The DEGs were mostly enriched in the biosynthesis process, ribosome, ribonucleoprotein complex, ribosome structural components, etc. according to GO enrichment analysis. The KEGG analysis showed that the DEGs were mostly enriched in amino acid biosynthesis, purine metabolism, carbon metabolism, phagocytosis, and other metabolic pathways. Also, out of 30 DEGs were identified to be associated with flowering, and the representative genes such as FT1, PIE1, GID1, GA20ox-1, GA20ox-2 were validated by qRT-PCR. The qRT-PCR results were consistent with the transcriptomic data, confirming the dependability of the transcriptome sequencing results. The findings would present essential candidate genes for revealing the mechanism of early flowering of sugarcane plants caused by S. scitamineum, and lay the foundation for disease resistance breeding.

Hevea brasiliensis is an important natural rubber-producing plant. Rubber particles (RP) in latex are important organelles for the synthesis of natural rubber, which can be divided into large rubber particles (LRP) and small rubber particles (SRP) according to the diameter. Although the specific mechanism of its regulation of natural rubber synthesis in response to exogenous ethylene stimulation has been studied. However, the specific regulatory mechanism of LRP and SRP in regulating natural rubber synthesis in response to ethylene stimulation is still unclear. In order to clarify the role of RP with different diameters in the synthesis of natural rubber, LRP and SRP stimulated by ethylene were isolated and the proteins of corresponding samples were extracted for differential protein analysis. 37 differential proteins in response to ethylene stimulation were identified in the LRP, which were involved in natural rubber biosynthesis, glycolysis/gluconeogenesis, carbon metabolism and amino acid biosynthesis, and some other metabolic pathways, including four members of the REF/SRPP family. 56 differential proteins were identified in SRP, which were involved in protein processing, endocytosis, splicing in endoplasmic reticulum, and some other metabolic pathways, including five members of the REF/SRPP family. The key differential accumulation protein REF138 had many isoforms with different isoelectric points (pI) and molecular weights (MW). REF138 isoforms below the standard pI (4.80) on LRP were down-regulated in response to ethylene stimulation, while isoforms above the standard pI were up-regulated to ethylene stimulation. Different from LRP, more isoforms of REF138 on SRP changed in response to ethylene stimulation, and isoforms with standard MW (14.7 kDa) were up-regulated in response to ethylene stimulation, while isoforms with higher than standard MW were down-regulated in response to ethylene stimulation. The function analysis of key differential proteins showed that there were interactions among the members of the REF/SRPP family. REF138, REF175, REF258, SRPP117 and SRPP204 may form protein complexes and bind to RP. In addition to the members of the REF/SRPP family, 20 proteins interacting with REF138 were mainly involved in the spliceosome and endocytic metabolic pathways, and 50 proteins interacting with REF258 were involved in the regulation of lipid metabolism and the synthesis of secondary metabolites. In conclusion, functional analysis of differential proteins and the interaction proteins responsive to ethylene stimulation on LRP and SRP might preliminarily reveal the metabolic regulatory mechanism of LRP and SRP in regulating natural rubber synthesis in response to exogenous ethylene stimulation.

Hypothenemus hampei is a new invasive pest in China. It is a main coffee pest and poses a great threat to the coffee industry. The purpose of this study is to clarify the biological characteristics and field occurrence rules of the insect, and to provide a theoretical basis for later monitoring and forecasting and comprehensive management of the insect. In this study, the morphological characteristics, developmental duration and fecundity of various developmental stages of H. hampei were observed at each stage in the indoor feeding conditions. The annual life cycle of H. hampei was observed in the field. The population dynamics and spatial distribution patterns of H. hampei in Wanning city, Hainan province were measured through systematic field investigation from 2021 to 2022 to clarify the biological characteristics and field occurrence of H. hampei, and provide a theoretical basis for the subsequent integrated pest management of H. hampei. The results showed that the developmental duration of egg, larval, pupal and adult stage of H. hampei was (6.75±0.65) d, (17.41±1.63) d, (6.45±1.15) d, (42.74±9.55) d, respectively. The average generation duration was (73.35±11.26) d. The main morphological characteristics of each stage were as follows: egg, elliptic, milky white, with smooth and shiny surface; larval, usually “C” shaped, milky white, slightly transparent, with brown head and no feet; pupal, milky white at the initial stage, and later turn brown, the head hidden under the pronotum; adult body, cylindrical, dark brown to black, shiny; male smaller than the female. Female adults usually laid eggs under dark conditions, the number of eggs laid by a single female was 11.85±1.69, and the ratio of male to female was 10.25∶0.95. The results of indoor and field observations showed that H. hampei had seven generations a year in Hainan, and there was no phenomenon of overwintering. The results of the field survey in 2021—2022 showed that the population of H. hampei began to increase slowly from January, and the incidence of H. hampei increased sharply from April to May, reached a maximum of 60.15% and peak in May, and then declined rapidly. In October, it remained at a relatively stable level. The population increased again in November, with another small peak, reaching 19.87%. In December, it decreased, but it showed a slow increase until March of the following year related to the number of fruits. The survey results on space and orientation showed that during the fruit development period, H. hampei preferred the middle layer (0.5-1.0 m) fruit spatially, and preferred the east and north directions in orientation, which may be related to light and temperature. The results of the four aggregation parameters showed that H. hampei belonged to the aggregation distribution in both horizontal and vertical directions.

The quality and performance of natural rubber (NR) are closely related to Hevea brasiliensis (rubber tree) varieties, tapping systems, seasonal variation and phenology etc. In order to uncover the annual change rules from April to December of NR qualities among different rubber tree varieties, we investigated the NR qualities from five clones including PR 107, RRIM 600, Reyan 917, Reyan 73397 and Reyan 879 cultivated in Danzhon of Hainan, China, and analysed the vulcanization characteristics and the mechanical properties of the vulcanized NR prepared from the latex harvested in May. The results showed that the mooney viscosity, protein percentage, volatile percentage, Wallace plasticity (P₀) and plasticity retention index (PRI) presented a downward or upward trend in an annual tapping cycle from April to December, which indicates that the NR quality parameters are affected by both genotypes and environmental factors such as weather and sunshine etc. The protein percentage in NR from the latex of the four rubber tree clones was more than 3.0% in December. The cure characteristics of NR from Reyan 917 were totally different from those of the other four rubber trees. Under the same tapping system of S/2 d/3, the tensile strength and the elongation at break of the vulcanized rubber from Reyan 879 was the smallest compared with the other four clones. The results would contribute to instructing the new variety breeding and rubber production on the one hand, and to providing scientific supports for high-performance NR manufacturing on the other hand.

Potted bitter melon was treated with Bacillus velezensis N46 to explore the mechanism of preventing powdery mildew of bitter melon. The prevention mechanism of N46 was studied by detecting the spore germination rate of powdery mildew pathogen (Podosphaera xanthii), changes in leaf defense enzyme activity, accumulation of reactive oxygen species, cell allergic necrosis, lignin accumulation, changes in the expression of disease-resistance related genes and disease-resistance pathways. The control effect of high concentration (6×10⁸ CFU/mL) of B. velezensis N46 on powdery mildew of bitter melon reached 59.05%. In the N46 treatment group, the range and peak value of the activity of defense enzymes POD, CAT and SOD increased significantly, the accumulation of reactive oxygen species (ROS) increased significantly, the rate of anaphylactic necrosis increased significantly, and the rate of lignin accumulation in cell wall was significantly enhanced. N46 had a significant inhibitory effect on the conidial germination of pathogen powdery mildew. The expression levels of JA reactive marker lipoxygenase gene (LOC111018837), SA reactive marker gene (LOC111017362) and peroxidase gene (LOC111021192) associated with allergic reaction and cell wall strengthening were detected in the N46 treated bitter melon. Compared with the control group, the expression levels of the genes increased significantly when bitter melon was infected with the powdery mildew bacteria, and the expression levels of JA reactive marker genes in the treatment group were also higher than those in the control group when there was no contact with pathogenic bacteria. The results indicated that N46 treated bitter melon maintained a certain level of “preactivation” of resistance genes when it was not exposed to pathogenic bacteria, but showed a higher expression level when it was exposed to pathogenic bacteria. Finally, the JA response pathway was inhibited by ibuprofen (IBU), and the control effect of B. velesiensis N46 on powdery mildew of bitter melon was almost disappeared, suggesting that the generation of N46 induced powdery mildew resistance of bitter melon depended on JA pathway. In conclusion, B. velezensis N46 has a good control effect on powdery mildew of bitter melon by inhibiting the conidium germination of megalomycesfoliata and inducing JA pathway dependent resistance of bitter melon. This study would provide a new method for the biological control of powdery mildew of bitter melon and a theoretical basis for the effect of B. velezensis on the control of powdery mildew of bitter melon.

Biochar was modified with different concentrations of hydrogen peroxide, and the differences in its structural characteristics were analyzed to study the modification effect of hydrogen peroxide on biochar obtained from banana stem and the effect of modified biochar on Cr absorption of maize under Cr stress. The effects of modified biochar on the growth, Cr uptake and accumulation of maize under Cr stress were studied. With the increase of hydrogen peroxide concentration, the number of oxygen-containing functional groups on the surface of biochar increased, while the aromatics decreased and the polarity increased. After the modification, the surface of biochar was smooth, the pore diameter increased, and the specific surface area and pore volume decreased with the increase of hydrogen peroxide concentration. Modified biochar by 20% and 30% hydrogen peroxide mainly fixed heavy metals through the adsorption of functional groups, reduced its biological activity, and reduced the Cr absorption and accumulation by corn. The study showed that 20% and 30% hydrogen peroxide significantly changed the surface structure of biochar, which was conducive to alleviating the toxicity of heavy metal Cr to corn plants. 30% hydrogen peroxide modified biochar promoted the growth of corn under Cr stress.

The antioxidant activity, total polyphenol and total flavonoid content differences of local Hainan specialty teas (Moringa Tea, Kuding Tea, Wuzhishan Green Tea, Baisha Green Tea, Wuzhishan Black Tea, Languiren and Partridge Tea) were evaluated. Results revealed significant variations in antioxidant activity among the teas. The antioxidant activity of the tea extract exhibited a dose-dependent relationship with sample concentration and demonstrated excellent thermal stability. The total polyphenol and total flavonoid content of the teas was ranged from 9.80% to 22.84% and 0.90% to 4.67%, respectively, and the total polyphenol content of Wuzhishan Green Tea was the highest, which was 2.33 times that of Moringa Tea. The difference in total polyphenol content of Kuding Tea, Wuzhishan Black Tea, Languiren, and Partridge Tea was not significant, while the total flavonoid content of Wuzhishan Green Tea was the highest, and the total flavonoid content of Wuzhishan Green Tea was 5.18 times that of Moringa Tea. The difference in total flavonoid content of Wuzhishan Black Tea, Languiren, and Partridge Tea was not significant, and the total polyphenol and total flavonoid content of Wuzhishan Green Tea were the highest among the teas. The seven tea extracts had antioxidant reduction ability, and the tea polyphenol content and total flavonoid content showed a good quantitative relationship with the scavenging ability of free radicals. Moringa Tea had the strongest ability to scavenge ABTS, Wuzhishan Black Tea had the strongest ability to scavenge superoxide radicals, and Baisha Green Tea had the best antioxidant effect overall, with the reduction ability, DPPH scavenging ability, hydroxyl radical scavenging ability were the strongest. The antioxidant properties of the seven tea extracts did not change significantly when incubated at different temperature conditions and boiling water, indicating that the seven tea extracts had better thermal stability. This study shows that Hainan specialty teas are rich in total polyphenols and total flavonoids and exhibit strong antioxidant abilities, providing a theoretical foundation for further development and utilization of Hainan specialty teas.

KOH was used as the activator combined with ultrasonic treatment to treat rubber seed shell to prepare activated carbon, and the best preparation conditions were optimized. The surface structure of the chemical carbon was regulated by controlling the preparation and processing conditions. The physical and chemical properties of the active carbon were characterized by specific surface area voidness analyzer, FT-IR, SEM, element analyzer, and TGA. The adsorption capacity of methylene blue and iodine was investigated. The optimal preparation conditions were reagent∶material ratio 1∶1, ultrasonic action for 60 minutes, activation time for 60 minutes, and activation temperature of 700 ℃. Activation temperature had the greatest impact on the adsorption capacity of activated carbon, followed by the reagent to material ratio and ultrasonic time, with the activation time having the smallest impact. The absorption of methylene blue was 400 mg/g, and iodine was 1340.2 mg/g, respectively. The yield was 25.9%, the specific surface area was 1034.5009 m²/g, and the total pore volume was 0.9511 cm³/g with ultrasonic pretreatment (UAC). The adsorption value of methylene blue was 300 mg/g, iodine adsorption value was 894.0 mg/g, yield was 20.8%, specific surface area was 690.2461 m²/g, total pore volume was 0.6830 cm³/g without ultrasoni pretreatment (NAC). Both contained hydroxyl, alcohol hydroxyl and carbonyl functional groups. This is conducive to the enhancement of adsorption performance, and the characteristics of cellulose, hemicellulose and lignin were obvious. The nitrogen adsorption isotherm of the rubber seed shell activated carbon was type Ⅰ. Activated carbon contained a large number of microporous structures with uniform distribution. There was no pore structure on the surface of the rubber seed shell, and there were a large number of pore structures on the activated carbon surface after KOH activation. The surface of UAC activated carbon was smooth and flat, with many rich and regular pore structures. In contrast, the pore surface of NAC had many small pores, and the surface was rough. The carbon (C) content in the rubber seed shells was rich. After KOH activation, the C content of the activated carbon prepared by ultrasonic treatment and activated carbon prepared without ultrasonic treatment increased from 56.81% to 75.97% and 64.89%, respectively. However, the content of hydrogen (H) and nitrogen (N) decreased, making it an excellent raw material for activated carbon. The TGA results indicate that the sample activated by KOH was more stable than the rubber seed shell, and the total weight of UAC and NAC samples tended to stabilize after losing 62% and 68%, respectively. In conclusion, the better performance of the samples prepared by ultrasonic pretreatment indicates that the cavitation effect of ultrasonic wave acts on the structural surface of the activated carbon, causing it to undergo structural changes, thus, the adsorption capability of the active carbon, the specific surface area, etc. are enhanced.

Phalaenopsis-hybrid Dendrobium is an important ornamental plant in tropical area and has high market values, with beautiful flower appearance and abundant flower colors. In this study, the protocorms and young seedling’s stem segments of commercial varieties, Den. Yaya Victoria, Den. Swirl and Den. Sonia Hiasakul, were used as the explants. The effects of different phytohormone combination on embryogenic callus induction, adventitious bud differentiation and plantlet regeneration were investigated. During the embryogenic callus (EC) induction stage, the best induction explants were protocorms and 2-month-old seedling stem segments and EC could be obtained after 30 days culture in dark condition. The best medium for EC induction of was MSD (MS+30 g/L glucose+1 g/L Hyponex+8 g/L agar) as the basic medium with 0.5 mg/L KT and 0.2-0.5 mg/L 2,4-D. The highest average induction rate of EC was 31.11%, 22.78%, and 50% for Den. Yaya Victoria, Den. Swirl and Den. Sonia Hiasakul, and the induction time for Den. Yaya Victoria was only 15 days from explants to EC. The best proliferation medium was MSD+0.5 mg/L IBA+0.5 mg/L KT, which maintaining EC in good condition without differentiation and the multiplication rate was 0.9. The best medium for differentiation was 1/2 MS+0.5 mg/L IBA+0.15 mg/L KT under light condition of 16 h one day, EC quickly differentiating and forming 2-3 leaf adventitious buds within 30 days, and finally regenerating into plantlet after 60 days in the same medium. The best rooting medium was 1/2 MS+30 g/L sugar+0.5 mg/L NAA+8 g/L agar, with rooting rate 100% and five roots in length 1.3 cm per plantlet. In this research, the EC induction, proliferation and differentiation media have a wide-spectrum and the EC regeneration pathway could lay a solid foundation for further molecular breeding of Phalaenopsis-hybrid Dendrobium.