The plant resources from nine islands of Xisha Yongle Islands and Xuande Islands (including Yongxing Island, Shi Island, Zhaoshu Island, Dong Island, Zhongjian Island, Jinyin Island, Chenhang Island, Guangjin Island and Shanhu Island) were surveyed in 2021 to 2023. Through field survey, specimen collection and identification, and literature review, 11 plants belonging to 10 genera in 8 families were recorded for the first time. The voucher specimens are deposited in the herbarium of Chinese Academy of Tropical Agricultural Sciences (ATCH). This study would provide important information for the plant resources of Xisha Islands.

Yinggeling area of the National Park of Hainan Tropical Rainforest preserves the largest and most intact tropical rainforest in South China. It is extraordinarily rich in fungal species, especially the fungi of Boletales with important ecological, scientific and economic values. Nearly 300 specimens of Boletales were collected from Yinggeling area in the past 10 years. On the basis of morphology, molecular phylogenetic analyses, ecological characteristics, and geographical information, a total of 82 species of Boletales, belonging to 37 genera and 5 families, have been identified. Among them, 2 genera and 26 species were typified from Yinggeling, 2 were new to China, and 20 were new to Hainan Province. In the Boletales in Yinggeling area, the only dominant family, with more than 10 species, was Boletaceae, accounting for 91.46% of the total species. There were 6 dominant genera (Aureoboletus, Boletellus, Neoboletus, Phylloporus, Strobilomyces, and Tylopilus), with more than 5 species, haboring 48.78% of the total species of this Order. Among the Boletales species from Yinggeling area, 20, 4, and 8 are considered to be edible, medicinal and poisonous mushrooms, respectively.

The 16S rRNA high-throughput sequencing analysis was conducted on the rhizosphere soil of Cassava South China No.12 under treatment without fertilization (CK), organic fertilizer (T₁), conventional fertilization applied with organic fertilizer (T₂), and reduced chemical fertilizer applied with organic fertilizer (T₃) by using the Illumina Nova 6000 sequencing platform to study the effects of chemical fertilizer application combined with organic fertilizer on the growth of cassava and the bacterial diversity and community structure in cassava rhizospheric soil. T₃ not only significantly increased the height and stem thickness of cassava, but also improved the yield of cassava, compared to CK. Cluster analysis was performed on the sequences based on 97% similarity, the OTUs numbers of CK, T₁, T₂ and T₃ are 3603, 1688, 1276 and 3317 respectively. Different fertilization methods altered the diversity and richness of soil bacteria, with the species diversity ranked from highest to lowest as CK>T₃>T₁>T₂. Based on PCoA and cluster analysis, the community composition of CK and T₃ was similar, the community composition of T₁ and T₂ was similar. The dominant phylum in cassava rhizospheric soil under different fertilization treatments were Proteobacteria, Bacteroidetes, Acidobacteria, Firmicutes, Actinobacteria and Chloroflexi. The relative abundance of Proteobacteria, Bacteroidetes and Actinobacteria increased under T₃ treatment, while the relative abundance of Firmicutes and Chloroflexi decreased. Redundancy analysis results indicated that available potassium was the main factor affecting the bacterial community in the cassava rhizosphere soil. In summary, the study demonstrates that reduced chemical fertilizer application combined with organic fertilizer not only increases the yield of cassava, but also changes the community structure and diversity of the bacterial in the rhizosphere soil. The results would provide a solid theoretical foundation for the development of a green, efficient, and sustainable cassava industry.

Hyper-spectral remote sensing technology was used to explore the estimation method of nitrogen content in the leaves of macadamia to achieve a rapid diagnosis of nitrogen nutrition in macadamia trees. Lincang and Xishuangbanna were chosen as the research area to obtain the spectral reflectance and nitrogen content of the leaves of macadamia varieties O.C and HAES344. Firstly, multiple mathematical transformations were performed on the original spectral reflectance using logarithmic transformation, derivative transformation, and their combinations. Then, the correlation between nitrogen content of macadamia leaves and spectral data of different transformation forms was analyzed. Under the principle of larger determination coefficient, the wavelength corresponding to the peak characteristic point in the determination coefficient curve was selected as the nitrogen sensitive wavelength, thus the corresponding spectral variables of nitrogen sensitivity were obtained. Stepwise regression was used to further optimize the nitrogen sensitive spectral variables, and the methods of multiple linear regression (MLR), partial least squares regression (PLSR), and support vector regression (SVR) were used to construct the nitrogen content estimation models for macadamia leaves. Finally, the performance of the models was tested using validation and test sets, respectively. The results showed that the MLR, PLSR and SVR models all performed well in estimation, and the ratio of performance to standard deviate (RPD) of both the validation and test sets were above 2.0. Among them, the PLSR was the optimal estimation model, its RPD of the validation set and the test set was 2.099 and 2.110, respectively. The 19 nitrogen sensitive spectral variables selected from 6 types of transformation spectral data, including reflectance (R), logarithmic transformation of reflectance (LR), first derivative of reflectance (FDR), first derivative of logarithmic transformation of reflectance (FDLR), second derivative of reflectance (SDR), and second derivative of logarithmic transformation of reflectance (SDLR) had strong stability in nitrogen spectral response. Based on the selected 19 nitrogen sensitive spectral variables, the conventional regression modeling methods could achieve good estimation results and had strong regional universality. In this study, nitrogen sensitive spectral variables were selected from a variety of transform spectral data, which provided a new idea for the nitrogen content estimation of macadamia leaves.

Hainan is the main producing area of noni in China. Short-term waterlogging stress is caused by typhoons occuring frequently in summer. However, there are few studies on the physiological response of noni to short-term waterlogging stress and after stress relief, and the effect of stress on yield is still unclear. In this study, Noni seedlings growing for 6 months were used as the experimental materials, and short-term waterlogging stress was simulated by potted continuous immersion for 15 days. Dry weight, net photosynthetic rate (P_n), proline (Pro) content of leaves, root activity (TTC), root malondialdehyde (MDA), peroxidase (POD) and superoxide dismutase (SOD) were measured at 1st, 3rd, 7th, 10th and 15th days after waterlogging. The relevant indexes were measured on the 1st, 7th and 15th day after stress relief, and the yield of waterlogged and non-waterlogged plots in the main producing areas was measured for 3 consecutive years. The results showed that the physiological response of Noni after waterlogging stress was rapid. Compared with non-waterlogging control treatment, the net photosynthetic rate of leaves decreased on the 1st day of waterlogging, the content of Pro increased, the content of MDA in roots increased, the root activity decreased, and the activities of antioxidant enzymes such as POD and SOD increased. All the indexes changed significantly in the first 7 days. However, after 7 days, the changes of TTC and SOD activity of roots remained significant, but the changes of other indexes were slow, indicating that leaves and roots gradually adopted corresponding strategies to adapt to waterlogging stress. The biomass root shoot ratio of Noni remained unchanged at the initial stage of waterlogging, but decreased significantly after 3 days, which also reflected that Noni plants had responded to waterlogging stress in a short period of time. After the stress was relieved, the physiological processes gradually recovered, and at 15 days, Noni photosynthesis and root activity basically recovered, but the content of peroxides such as MDA was still significantly higher than that of the control, indicating that the toxic effect of peroxides formed under early stress was difficult to eliminate in the short term. The multi-year yield of main producing areas shows that short-term but frequent waterlogging stress can lead to a significant decrease in yield, which is 21.64%–35.21%, which may be related to peroxide toxicity caused by stress. In summary, short-term waterlogging stress not only has a great impact on the physiological process of noni during stress, but also its adverse effects persisted for a long time after the stress is lifted, thereby affecting crop growth and yield. Therefore, for planting noni, the plots with higher terrain and better drainage should be in priority. In water-prone planting areas, water should be drained within 72 hours to minimize the adverse impact.

The study was aimed to explore the resistance to Colletotrichum siamense, dominant specie of rubber tree induced by Burkholderia arboris DHR18. The enzyme activity changes on the treatments of different concentrations of DHR18 fermentation broth and co-treatments of DHR18 with C. siamense CH-1 using rubber clone GT1 were studied. Five defensive enzymes including catalase (CAT), peroxidase (POD), phenylalanin ammonialyase (PAL), and superoxide dismutase (SOD) were assayed. Results indicated that treatments with 1×10⁸ CFU/mL, 1×10⁷ CFU/mL, 1×10⁶ CFU/mL of DHR18 fermentation broth showed significant higher activities of CAT, POD, PAL, SOD and PPO in rubber leaves compared to the control group. The enzyme activities with broth concentration 1×10⁷ CFU/mL were the highest. The activity peak of the five enzymes was 1 009.14, 29 138.67, 110.24, 902.42 and 148.00 U/g, respectively, which was 2.68, 3.35, 1.88, 3.97 and 4.51 times of the control group, respectively. Under the co-treatments of B. arboris DHR18 and C. siamense CH-1, treatment group inoculated with DHR18 fermentation broth before inoculated with CH-1, the enzyme activities were higher than other co-treatment groups, and significantly higher than that of the control group. Activity peak of CAT, POD, PAL, SOD and PPO was 1 230.85, 45 504.67, 117.53, 1 342.17 and 134.40 U/g, respectively. They were 4.56, 3.10, 2.04, 3.28 and 5.98 times that of the control group, respectively; The plate inhibition rate of strain DHR18 against C. siamense was 71.56%, the preventive effect against C. siamense on rubber saplings was 81.79%, and the control effect was 44.35%. The results showed that Burkholderia arboris DHR18 could promote the activity of defense-related enzymes in rubber trees and induce systemic resistance in rubber trees. The induced resistance may be one of the reasons for the control of C. siamense by B. arboris DHR18.

A new cassava variety Gui 1289 with excellent comprehensive traits such as good plant type, high yield, high starch, and wide adaptability was bred by systematic breeding procedures using SC5 as the maternal parent and SC205 as the paternal parent. The average yield of fresh roots for this variety was 49.92 t/hm² in regional test over the years, which was 24.21% higher than that of the control NZ 199. The average yield of fresh roots was 50.76 t/hm² in production test, which was 21.26% higher than that of NZ 199. The average starch content in regional test over the years was 30.22 g/100 g, an increase of 5.42 g/100 g compared to NZ 199. The average starch content in production test over the years was 29.96 g/100 g, an increase of 5.57 g/100 g compared to NZ 199. The field test of Tetranychus cinnabarinus showed moderate resistance. It is suitable for popularization in cassava planting areas such as Guangxi, Guangdong, Hainan and Jiangxi, and so on. This study would provide a new germplasm resource for achieving high-quality production of cassava in China, which is of great significance to increase the income of the farmers and increase the efficiency of enterprises

The microbial community of fruit peel tissues helps to improve fruit quality and resistance to pathogens. There are few reports on the community structure and diversity of endophytic microbes of pitaya peel tissues. This study analyzed the composition and diversity of the endophytic microbial communities in the peel tissues of young healthy fruits and diseased fruits at the early stage of canker disease, and predicted microbial functions to understand the characteristics, through Illumina MiSeq high-throughput sequencing technology. The results showed that there was no significant difference in the diversity and structure of the endophytic bacterial and fungal communities between healthy and diseased peel tissues of pitaya young fruits. In the peel tissues of healthy fruits, Proteobacteria, Actinobacteriota, Firmicutes, Bacteroidota, Deinococcota, Desulfobacteriota and Chloroflexi were the dominant bacterial phyla, and Ascomycota, unclassified_k_Fungi, Basidiomycota and Mucoromycota were the dominant fungal phyla. In the early stage of canker disease, the bacterial phyla Proteobacteria, Actinobacteriota and Deinococcota, as well as fungal phylum Ascomycota, significantly decreased, while bacterial phylum Desulfobacteriota and fungal phylum unclassified_k_Fungi significantly increased in average relative abundance. Compared with the healthy fruits peel, with differences in the proportion of the above microbes, the expression levels of chemoheterotrophy, aerobic chemoheterotrophy, methylotrophic and methanol oxidation functions of endophytic bacteria in diseased fruits peel significantly decreased, the proportion of potentially_pathogenic groups of endophytic bacteria significantly increased, the proportion of saprotroph, pathotroph, pathotroph symbiotroph of endophytic fungi significantly decreased, and the proportion of unknown trophic fungi significantly increased. The results would provide biological information on the endophytic microbes in pitaya fruits peel, to reveal the role in the occurrence of pitaya canker disease and provide theoretical basis for utilizing the function of beneficial microorganisms.

The pathogen of pitaya stem rot in Guangxi was isolated by the tissue separation method and the microbial control of the disease was selected. According to Koch’s rule, the pathogenicity was verified by in vitro experiments, and the pathogenic species were identified by the morphological and multi-gene sequence analysis. Then, the biocontrol bacteria were screened by the plate confrontation method. The results showed that two pathogenic fungi, Lasiodiplodia pseudotheobromae and Neoscytalidium dimidiatum, were isolated from the decayed stems of pitaya, of which L. pseudotheobromae was the first reported to cause pitaya stem rot in China. Taking L. pseudotheobromae PY6 as the target pathogen, Bacillus subtilis L3-4 with the best control effect was obtained from 34 strains of pitaya endophytes screened, which could make the mycelium of PY6 entangled and broken. The sterile fermentation filtrate and the sterile fermentation broth after 100 ℃ treatment had antibacterial effect, and the prevention effect could reach 72.08% and 71.16%, respectively. But it did not produce volatile compounds that inhibited the growth of PY6 strain. In addition, strain L3-4 exhibited inhibition to Botryosphaeria dothidea, Fusarium pseudograminearum, F. oxysporum and N. dimidiatum with inhibition rate 77.65%, 73.13%, 64.07% and 62.01%, respectively. This study clarified the pathogenic pathogen responsible for pitaya stem rot in Guangxi. The screened biocontrol bacteria could be used as candidate strain for controlling pitaya stem rot. The result would provide a theoretical basis for diagnosing and biologically controlling pitaya stem rot.

Sisal hybrid variety of H.11648 is the main cultivated commercial variety in China. Despite of its ability to produce high fibre yield per unit area, this variety is highly susceptible to diseases. Sisal zebra disease, caused by Phytophthora nicotianae is among the diseases of economic importance affecting the variety. Several control measures like the adoption of good agricultural practices, the use of disease resistant variety and the use of chemical control are suggested in sisal zebra disease control. However, none of them seem to be sustainable due to the existing agricultural practices. Most of the existing measures are not only time-consuming but also costly due to labor intensification and high cost of purchasing agricultural chemicals which on another hand can pollute the environment and create resistance to the plants. Developing resistance variety will obviously take long time due to the long life cycle of sisal. It is very important to develop sustainable disease control methods which are environmental friendly to adopt the climate change agenda. The use of microorganisms to control the diseases is of great importance. In this study, an antagonistic strain PaHNHK01 was successfully isolated by using Phytophthora nicotianae as the target pathogen. PaHNHK01 was identified as Pseudomonas aeruginosa based on morphological, physiological and biochemical characteristics and gene sequence analysis. The antibacterial activity and control effect of PaHNHK01 were measured under in vitro condition. The results showed that, PaHNHK01 had the ability of organophosphorus and inorganic phosphorus, nitrogen fixation and iron production. Additionally, PAHNHK01 had the inhibition rate of 89.79% against P. nicotianae. The fungus effectively inhibited the mycelial growth of P. nicotianae, and the antagonistic pathogens showed decreased sporulation ability, mycelial enlargement deformity and increased branching. The control effect of PaHNHK01 on sisal zebra disease in vitro was 88.62%. PaHNHK01 aseptic fermentation liquid had obvious bacteriostatic effect on pathogenic bacteria, and its EC₅₀ value was 20.3679 μL/mL. When the concentration of PaHNHK01 crude extract was 80 μg/mL, the antibacterial rate was 89.36%, and the EC₅₀ value of PaHNHK01 crude extract was 11.9456 μg/mL. We further observed the antagonistic effects of the strain PaHNHK01 on 13 different plant pathogens, indicating that the strain PaHNHK01 had good biocontrol potential and could be developed as a biocontrol product. The results would provide a strong research basis for the biological control of sisal zebra disease.