Watercore is a kind of physiological disease of pineapple fruit, which causes the intercellular space of pineapple pulp tissue to be filled with cell fluid and appear as water-soaked, which seriously affects the edible value and commercial value of the fruit. Watercore has troubled the development of pineapple industry for many years, but its mechanism is not clear. In order to explore the pathogenesis of watercore in pineapple, this study took the main pineapple cultivar Comte de paris as the material, the paraffin section method was used to observe the process of watercore in pineapple fruit and the different tissue parts of normal and watercore fruit (flower stock, carpel, fruit sequence axis). The results showed that the cell structure of pineapple pulp was closely related to watercore: the cell structure of normal fruit pulp was complete, the cell space was obvious, the vascular bundle was intact, the phloem cells were arranged tightly and neatly, and the xylem ducts were arranged regularly. However, fruit flesh cells in watercore are squeezed and deformed, and the cell wall rupture results in incomplete cell structure, destruction of vascular bundle morphology, extrusion and deformation of phloem, and destruction of xylem ducts to form a cavity. With the deepening of the onset process of watercore, the xylem cavity becomes larger. Through the morphological observation of different tissue parts of normal fruits and fruit with watercore, it was found that the changes of cell structure caused by watercore in different tissue parts were basically the same. There were obvious differences in vascular bundle morphology and structure in different tissue parts. The vascular bundles in the fruit sequence axis and receptacle were in accordance with the typical characteristics of vascular bundles in monocotyledons. The vascular bundles were surrounded by a sheath composed of thick-walled mechanical tissue at the periphery of each vascular bundle. On the other hand, there were more sachmatous cells at both ends of the vascular bundle. The inner part of the vascular bundle sheath contains primary phloem and primary xylem without the middle bundle cambium. The vascular bundle structure of the carpel was atypical, and most of the vascular bundles were not surrounded by vascular sheath. Vascular tissues in the fruit sequence axis were the most developed, followed by receptacle, and vascular tissues in the carpel were the least developed. These results revealed the morphological changes of pineapple watercore during its occurrence and provided reference for further research on the mechanism of watercore.

GATA transcription factors play an important role in regulating plant response to abiotic stress. In this study, an IbGATA16 gene was cloned from sweet potato and analyzed by bioinformatics. The expression pattern of IbGATA16 gene in sweet potato under drought and salt stress was analyzed. Experimental results show that the full length of IbGATA16 CDS sequence is 420 bp, and it encodes 139 amino acids. The molecular weight of IbGATA16 was 15.39 kDa, isoelectric point was 9.97. The full length of the genome is 582 bp, including 3 exons and 2 introns. IbGATA16 is an unstable hydrophilic lipid-soluble protein., and its subcellular localization predicts that the protein is located in the nucleus. It has the C-X₂-C-X₁₇-C-X₂-C domain and belongs to the typical GATA class of transcription factors. There are many cis-acting elements in the 1382 bp upstream promoter sequence of IbGATA16 gene, such as MYB, ABRE, and GARE-motif. The results of multiple sequence alignment and phylogenetic tree analysis showed that IbGATA16 protein was closely related to ItGATA16. The sequence of the N-terminal zinc finger domain is highly consistent, suggesting a possible similar function. The results of real-time fluorescence quantification showed that IbGATA16 was expressed in root, stem and leaf tissues of sweet potato, and the expression level of IbGATA16 in leaves was significantly higher than that in stem and root tissues. IbGATA16 was significantly induced by drought and salt stress, and after 0, 1, 3, 6, 12 and 24 h of drought and salt stress, the expression of IbGATA16 was significantly higher than that of 0 h. Under drought stress, the expression of IbGATA16 reached its peak at 1 h, and under salt stress, the expression of IbGATA16 reached the maximum at 3 h. IbGATA16 positively responds to drought and salt stress in sweet potato. These results indicated that IbGATA16 gene was involved in the response of sweet potato to drought and salt stress, and the regulation of IbGATA16 gene was different in roots, stems and leaves. This study provides a reference for further research on the biological function of IbGATA16 and its mechanism in response to stress in sweet potato.

Cassava leaves are rich in abundant flavonols, and efficient extraction and analysis methods are crucial for the evaluation of flavonol content in the cassava leaves. This study aims to optimize the extraction and detection methods for four flavonols (myricetin, rutin, nicotiflorin, narcissoside) in cassava leaves and to analyze the influence of different cassava varieties, harvesting periods, and maturity on the content of these flavonols. The results indicated that using a 50% ethanol-water solution, a liquid-to-material ratio of 1∶50 (g/mL), an ultrasonic extraction temperature of 50 ℃, and an ultrasonic extraction time of 60 minutes could effectively extract the four flavonols in the cassava leaves. The combination of different C18 chromatographic columns in HPLC-DAD effectively separated the four flavonoids present in the cassava leaves. The results of the method validation showed that the four flavonols exhibited good linear correlations within a certain concentration range, with R² values of 0.9999, 0.9999, 0.9999 and 0.9998, respectively. The detection limits ranged from 6.0 mg/kg to 10.0 mg/kg, and the quantification limits ranged from 20.0 mg/kg to 32.0 mg/kg. The detection method demonstrates good system adaptability, with retention time and peak area relative standard deviations (RSD) being less than 1%. The samples showed good stability in terms of intra-day, inter-day, and intra-month variations, with RSD in content variations ranging from 0.44% to 3.57%. The average recovery rates of the method ranged from 92.68% to 109.14%, all with RSD values less than 6.0%. Utilizing the established extraction and analysis methods, the study analyzed the content of the four flavonols in 30 cassava germplasm resources. Rutin and nicotiflorin maked up 93.50% to 99.30% of the total flavonol content in the cassava leaves, with the levels primarily determining the total flavonol content. However, the correlation order for the total flavonol content among different varieties was rutin>narcissoside>nicotiflorin>myricetin. Analysis of flavonol content in the cassava leaves from different harvest times and maturity levels of cassava germplasm revealed that in most cases, the levels of rutin, nicotiflorin and narcissoside were higher in the leaves harvested at 270 days compared to those harvested at 180 days, with myricetin varying by variety. Except for SC09, the levels of myricetin, rutin and nicotiflorin were higher in the young leaves compared to the tender and mature leaves in different cassava germplasms. The content of narcissoside in mature leaves (except for flower leaf cassava) was higher than that in young leaves and tender leaves. The results would provide an evaluation basis for the development and utilization of cassava flavonols in the selection of raw materials and quality control, and lay a foundation for revealing the accumulation rules of cassava flavonols.

Cassava is an important food crop, energy crop and industrial raw material. Cassava mealybug (Phenacoccus manihoti Matile-Ferrero) is a dangerous quarantine pest in the world, the cultivation and utilization of insect-resistant cassava cultivars can effectively block its colonization. Mining insect-resistant secondary metabolites and the regulatory genes is one of the important strategies for insect-resistant breeding. Flavonoids are unique secondary metabolites for plants to resist biotic and abiotic stresses, but the function of flavonoids and the synthesis pathway genes in cassava resistance to cassava mealybug is still unclear. Based on this, this study analyzed the expression levels of flavonoid synthesis pathway-related genes (CHS, CHI, FLS, LAR, DFR, F3H, CCoAOMT, C4H, C3'H and ANR) and flavonoid content in the leaves of insect-resistant (C1115, SC9, Myanmar) and insect-susceptible (KU50, SC205 and Bread) cassava cultivars after being damaged by cassava mealybug for different time (0, 1, 4, 8 d). Although the expression of CCoAOMT, C3'H, ANR and C4H in the leaf was up-regulated after feeding, there was no significant difference compared with that before damage, and there was no significant difference in the expression level between the resistant and susceptible cassava cultivars. In contrast, the expression levels of CHS, CHI, FLS, F3H, DFR and LAR genes were significantly higher than those before damage, and in the same damage time, the expression levels of the six genes in the insect-resistant cassava cultivars were also significantly higher than those in the insect-susceptible cassava cultivars. Further correlation analysis showed that the expression levels of CHS, CHI, FLS, F3H and LAR genes were significantly positively correlated with the insect resistance of cassava cultivars. In addition, the results of total flavonoid content determination showed that the total flavonoid content increased significantly after one day of damage compared with that before damage, and the total flavonoid content of insect-resistant cassava cultivars was significantly higher than that of the insect-susceptible cassava cultivars after 4 days of damage. Correlation analysis showed that the total flavonoid content was also significantly positively correlated with the insect resistance of cassava cultivars. Therefore, it is speculated that the increase of flavonoid content and the significantly up-regulation of CHS, CHI, FLS, F3H and LAR in the insect-resistant cassava cultivars may be related to the resistance to cassava mealybug. This study would provide an important preliminary basis for the in-depth analysis of the molecular mechanism of flavonoid synthesis genes regulating the insect-resistant defense response of cassava to mealybug, as well as the molecular design and breeding of cassava insect-resistant.

The problem of soil salinization in my country is becoming more and more serious. Rice is the preferred food crop for the improvement of salinized land, but salt stress is one of the main abiotic stresses that influence the growth and yield of rice. In order to fully understand the effect of salt stress on the rice, 31 varieties (lines) of tropical rice with different salt tolerance were used as experimental materials, and experiments were carried out by hydroponics in seedling stage incubator and potted soil cultivation method in the whole growth period, to study the effects of 0 NaCl (CK), 0.3% NaCl and 0.6% NaCl on the growth, physiological and biochemical characteristics, and yield composition of tropical rice. The result showed that: (1) The seedlings and roots growth of tropical rice were inhibited under salt stress. The seedling height and root number were significantly decreased with the increase of NaCl concentration, the root length in 0.3% NaCl and 0.6% NaCl treatments was significantly lower than CK treatments; and the fresh weight of seedling in 0.6% NaCl treatments was significantly lower than CK and 0.3% NaCl treatments. (2) Chlorophyll accumulation of tropical rice leaves were decreased under salt stress. The contents of chlorophyll a, chlorophyll b and Car in the treatments with 0.3% NaCl and 0.6% NaCl concentrations were significantly lower than CK treatments. The accumulation of proline (Pro), malondialdehyde (MDA) and Na⁺ were increased. The content of Pro and MDA and Na⁺ in the treatments with 0.6% NaCl concentration were significantly higher than treatments with CK and 0.3% NaCl concentration. The accumulation of K⁺were decreased. The K⁺ content in the 0.3% NaCl and 0.6% NaCl concentration treatments was significantly lower than the CK concentration treatments. (3) Under salt stress, the tiller number, panicle number, panicle length, panicle grain number, thousand-kernel weight and yield of per plant were significantly decreased with the increase of NaCl concentration.

Cell wall degrading enzymes are important pathogenic factors of many pathogenic fungi, among which xylanase, as the most important hemicellulase, plays an important role in the process of host cell wall degrading by filamentous fungi to achieve host infection. In this study, RT-PCR was used to clone the coding region of xylanase GpTR1774 gene of Ganoderma pseudoferreum strain HD3 and analyze its bioinformatics. The root of Hevea tissue cultured seedlings Reyan 73397 were infected with HD3, meanwhile infection and destruction process of root cells were observed by electron microscopy. The gene expression of GpTR1774 was determined by qRT-PCR. The results showed that the total length of GpTR1774 cDNA was 780 bp, encoding 259 amino acids, among which the most abundant amino acid was alanine (Ala), accounting for 15.1%. The molecular weight of GpTR1774 protein was 28.12 kDa, fat coefficient was 81.93, and the isoelectric point was 9.07. It was a hydrophilic protein with 15 phosphorylation sites, no signal and peptide transmembrane domain, and was located in the cell solute. The main components of the secondary structureα-helix and random curling are the main components of the secondary structure of GpTR1774 protein, accounting for 38.10% and 41.31% of the amino acid sequence, respectively. Phylogenetic analysis showed that GpTR1774 gene had the highest similarity with xylanase gene of Ganoderma boninense, reaching 87.5%. qRT-PCR showed that the overall gene expression trend of xylanase GpTR1774 was firstly increased and then decreased. The expression level of GPTR1774 increased significantly on the 3rd and 4th day after infection, and reached the highest level on the 4th day, about 16 times of the initial level. The results of this study indicate that the xylanase GpTR1774 gene was likely to be involved in the pathogenesis of G. psedoferreum, providing reference for the pathogenesis analysis and green prevention and control of G. psedoferreum.

Polysaccharide is a quality marker of Polygonatum odoratum, which has significant pharmacological effects in immune regulation and anti-tumor. As one of the key enzymes in polysaccharide synthesis, sucrosesynthase (SUS) has always been an important research field to reveal the synthesis of plant polysaccharides. Based on transcriptom data of Polygonatum odoratum, the SUS gene family members were identified by bioinformatics, and their expression profiling were analyzed using qPCR. The results showed that eight PoSUS gene were identified, their protein ranged from 111 to 310 amino acid residues (aa) in length, and relative molecular weight varied from 12.81 kDa to 35.43 kDa, isoelectric point (pI) in the range of 5.83 to 9.18; phylogenetic analysis indicated that eight PoSUS genes were divided into 3 subfamily, and the subfamily Ⅲ included the largest PoSUS genes family member; subcellural localization analysis showed that most of PoSUS proteins were located in chloroplast. Additionally, expression patterns analysis revealed that PoSUS1 and PoSUS6 genes were preferably expressed in rhizome, and the transcript levels of PoSUS1 and PoSUS2 were higher in high-polysaccharide cultivar HN1 than those in a low-polysaccharide cultivar AH2. In addition, the CDS of PoSUS1 gene were cloned from HN1 and AH2, there are three amino acid difference between HN1 and AH2, which located in sucrose synthase domain. Our findings can laid a basis for the further study of functional analysis of SUS genes, and provided a theoretical basis for analyzing molecular mechanism of the formation mechanism of medicinal quality of Polygonatum odoratum.

Marine actinomycetes possess great capacity in producing special metabolites due to their special environment and unique properties in physiological characters and genetic background. In this study, sponge was used as isolation material to explore the resources of symbiotic actinomycetes with antibacterial activity. Firstly, an active actinomycetes strain, ITBB-ZK-a5, was isolated and purified from the sample of Xisha sponge by plate separation method. The strain was identified as Streptomyces by analysis of the phylogenetic tree based on 16S rRNA gene sequence and colony morphological characteristics. Secondly, the inhibitory spectrum of strain ITBB-ZK-a5 against plant pathogenic fungi was studied by plate confrontation method. The results showed that ITBB-ZK-a5 had a broad antibacterial spectrum, in which the 16 tested pathogenic fungi were inhibited significantly. ITBB-ZK-a5 also showed good antibacterial activity in 14 days and 30 days. In order to explore the reason why strain ITBB-ZK-a5 can inhibit the growth of pathogenic bacteria, the antibacterial activity of asepsis agar from the ITBB-ZK-a5 edge were determined, and the results showed that the antibacterial rate were negatively correlated with colony distance. This result revealed that actinomycetes maybe can secrete active substances to inhibit the growth of pathogenic bacteria. Thirdly, the strain had a good antibacterial stability by detecting the antimicrobial activity of five continuously dynasties. Again, light stability and thermal stability of the ITBB-ZK-a5 crude extracts from the rice solid fermentation were tested through the filter method; the results show that with the increase of bath temperature and UV duration, the antibacterial activity of the strain ITBB-ZK-a5 crude extracts were decreased. Finally, the EC₅₀ value of strain ITBB-ZK-a5 against anthrax diseases of banana and papaya were determined. Plant diseases infected by fungi are the main agricultural diseases, and chemical pesticides are the most commonly used method in diseases control. However, the widespread use of chemical pesticides will not only enhance crop resistance to drugs, but also cause pollution to the ecological environment. More importantly, pesticide residues also have a certain influence on human health. Therefore, the common goal of the world is to find more green, efficient and safe control methods. Actinomycetes are found to have biological control effects. The symbiotic actinomycetes isolated from sponges have an inhibitory effect on pathogenic fungi of tropical crops, which can be applied to efficient diseases control, conforming to the concept of green environmental protection. In this paper, we isolated and identified the strain ITBB-ZK-a5, symbiotic actinomycetes from South China Sea sponge, which has the activity of inhibiting pathogenic fungi of various tropical crops, and studied its antibacterial activity, providing a research basis for the development and utilization of biocontrol strains in the future.

The study of source/sink relationship has important theoretical research and technical application value in crop yield and quality formation. With the interdisciplinary integration of crop genetics and breeding, plant physiology and molecular biology, the study of source-sink relationship has made important progress in recent years by integrating molecular biology techniques, plant hormone signal transduction and many other new technologies and methods. In this paper, the research progress is reviewed from two aspects: source/sink relationship theory and regulation. The mechanism of glucose metabolism and hormone regulating source/sink relationship was emphasized, and the mechanism of cultivation measures improving yield by coordinating source/sink relationship was analyzed. Combined with the research progress on the mechanism and regulation of rubber trees, an important tropical cash crop. This lay a foundation for the theory of source/sink relationship in natural rubber industry and provide technical guidance for the creation of rubber latex flow control technology.

This article is the first to conduct prevention and control experiments on rubber tree powdery mildew and anthracnose using a heavy-load plant protection UAV (FBH300T), analyzing the effects of flight heights of 3 m, 5 m, 7 m, and application amount of 60 L/hm², 90 L/hm², 105 L/hm² on the distribution of droplet deposition on the upper and lower leaves of rubber trees. This study found that flight altitude and application amount has a very significant impact on droplet density and droplet coverage. It has been selected that the optimal application parameters for this aircraft model are a flight height of 5 m above the canopy, an application amount of 90 L/hm², and a flight speed of 5 m, this study utilized a new specialized agent 19% Baoyeqing ME, which can simultaneously treat various leaf diseases of rubber trees, as well as efficient agents such as 60% sulfur powder SC, 45% pentazolamide EW, and 50% sulfur triadimefon SC, which were used in conjunction with heavy-load plant protection UAV (FBH300T) to analyze the control effects of each agent on the powdery mildew and anthracnose of rubber trees. The results showed that among the four single agents, the 50% sulfur triadimefon SC had the best control effect on powdery mildew, followed by the 19%Baoyeqing ME; The best control effect on Anthracnose is 19% Baoyeqing ME, followed by 45% pentazole imidamide EW. Under the mixed application of chemical agents, the best control effect against powdery mildew and anthracnose was achieved by mixing 19% Baoyeqing ME and 60% sulfur powder SC at a ratio of 1∶1, followed by mixture of 19% Baoyeqing ME and 50% sulfur triadimefon SC at a ratio of 1∶1. The experimental results can provide a good reference basis for the maturation of UAV flight defense technology and the selection of special flight prevention agents for rubber tree leaf disease.