Cassava is the sixth-important grain crop in the world and the major cash crop in Southern China. Now cassava related industries play an important role in the local agricultural economy. Various kinds of diseases often happen and cause serious economic losses in the field, which become an important issue. This paper briefly reviewed the progress of cassava disease research, including the slow development stage from the founding of the P. R China to the 1980s, the fast development stage from the 1990s to the 2010s, and the rapid development stage after the 2010s. The latest research progress is the core part of this paper. Currently, there are four categories and eleven kinds of diseases that harm cassava in China. Cassava bacterial blight (CBB) is the most serious disease, and brown leaf spot occures in the largest area. Cassava mosaic disease (CMD) is the worst disease in the world, which has invaded mainland China. Chinese Academy of Tropical Agricultural Sciences and other institutions have launched the research of disease database construction and intelligent monitoring technology. The researcher had estimated the risk of five kinds of dangerous disease to cassava planting industry of China. For CMD and cassava brown streak disease, the research on the resistance evaluation of the main varieties, damage mechanism of virus, and detection methods were studied. As far as CBB, monitoring technology, genome sequencing of pathogen, pathogenic and copper resistant mechanisms, genetic variation of pathogen populations, selection of resistant germplasm and its function mechanism were investigated. The effective bactericide for CBB was screened, the efficient spraying and biological control technology were formed, along with the stem disinfection method was popularized in the field. In term of CMD, the occurrence area, virus identification, key factors for long range diffusion were confirmed in China, and significant advance was achieved in virus damage and propagation mechanism. The advance of monitoring and control technology on another seven kinds of common diseases was also expounded in this paper. With the development of the national economy, there have been new trends in China's cassava planting industry, such as food consumption and scaling planting. The authors further look forward to the number of participating institutions, the speed of scientific research progress, the boosting role of multidisciplinary integration, and new research hotspots will emerge in the future. This article would help relevant practitioners to better understand the current situation and research progress of cassava diseases in China, and also provide a reference for the research and application of monitoring technologies of other crop diseases in tropical areas.

Cassava (Manihot esculenta Crantz) is the sixth-largest food crop in the world, nearly 700 million people in the world tropical regions take it as the primary food source, and it is also an important raw material for the production of starch, modified starch, fuel ethanol and other chemical products and feed in China. It plays an important role in eradicating hunger, poverty alleviation and rural revitalization in tropical areas. Cassava root is rich in starch, which can provide energy for livestock and poultry growth. Cassava stems and leaves are rich in protein, cellulose and vitamins and other nutrients, thereby becoming a high-quality protein feed resource. Energy value of cassava is similar to that of corn, thus boasting great development potential as the feed. In recent years, it has achieved good results in the breeding of livestock and poultry such as pigs, sheep and chickens. Therefore, it is of great significance of using cassava as energy feed and replacing corn and other raw materials to mitigating competition for food between human beings and livestock and improve the economic benefits of breeding. This article comprehensively analyzed the nutritional value of cassava and the research progress of its feed application, and put forward specific suggestions for further research and utilization to provide reference for the development of cassava feed industry in the future.

Chalcone synthase (CHS) is the first limiting enzyme in flavonoid synthesis pathway and plays an important role in flower color formation, growth and development, and abiotic stress. In order to clarify the characteristics of cassava MeCHS gene family and its expression in cassava postharvest physiological deterioration (PPD), the MeCHS gene family was analyzed using bioinformatics, including physicochemical property and subcellular location. qRT-PCR was carried out to detect the expression levels of MeCHS genes in different varieties, different tissues and PPD process. The genes with significant relative expression were selected for cloning and subcellular localization verification. A total of 5 MeCHS gene members were identified in the cassava genome. The secondary structure analysis showed that the MeCHS gene family was mainly composed of α-helices and random coils. Tissue specific expression indicated that the expression levels of MeCHS genes were higher in stems. The major expressed MeCHS genes in cassava were MeCHS1, MeCHS2 and MeCHS3; and the expression levels of these three genes were gradually increase with PPD. MeCHS1, MeCHS2 and MeCHS3 were successfully cloned; and fluorescence transient expression showed that MeCHS1, MeCHS2 and MeCHS3 were localized in the cytoplasm, which was consistent with the predicted results. This study will provide a theoretical basis for further revealing the function of MeCHS gene family and improving the PPD tolerance of cassava.

Protein phosphatase 2C (PP2C) plays a key role in the ABA signaling pathway. In order to investigate the response process of the PP2C gene to abiotic stress in cassava, MePP2CAb gene was cloned from Arg7 in cassava using the RT-PCR technique. Bioinformatic analysis, autoactivation activity analysis, promoter activity analysis, and expression pattern analysis of the MePP2CAb gene under different stress and hormone treatments were conducted. The results showed that (1) the total length of the MePP2CAb gene was 1296 bp, encoding 431 amino acid residues. The MePP2CAb protein had a relative molecular weight of 47.08 kDa and a theoretical isoelectric point of 5.5. It exhibited structural domain characteristics of the PP2C family. Protein sequence analysis showed that MePP2CAb was most similar to PP2C sequences of Hevea rubber and Jatropha jatropha, with consistencies of 82.75% and 74.01%, respectively, and a conserved C-terminal. These results indicated that MePP2CAb belongs to the PP2C family. (2) The expression of the MePP2CAb gene was found to be higher in cassava storage roots, stems, and leaves, with the highest expression observed in storage roots. (3) MePP2CAb demonstrated self-activation activity, and its full-length promoter exhibited high activity. (4) The MePP2CAb gene belongs to the core ABA pathway, and promoter sequence analysis showed that it contained ABRE (abscisic acid responsiveness) elements, MeJA response elements, and a drought-induced motif. Under different stress and hormone treatments, low temperature and SA treatment significantly repressed the MePP2CAb gene, while mannitol, NaCl, ABA, and MeJA significantly induced its expression. In addition, the interaction between MePP2CAb and MePYL1 was also observed. These results suggest that MePP2CAb may be responsive to abiotic stress in cassava, although its role as a positive or negative regulatory factor remains unclear. These results provide a clue for further investigation into the role of the MePP2CAb gene in the ABA signaling pathway and the improvement of cassava's adaptation to abiotic stress.

Cassava is an important food crop in tropical regions, and one of the main breeding goals is to cultivate new lines with high β-carotene, low cyanogenic glucoside and waxy taste. In order to screen promising edible lines from breeding materials, the study developed a MATE-SNAP marker based on a mutation of G→A in the coding region of cyanogenic glucoside transporter gene MATE which resulted to amino acid change and affected its transmembrane structure stability. Combining with the β-carotene PSY2-SNAP and waxy quality GBSSⅠ-SNAP markers, 12 parent lines, carrying 1-2 target alleles, were selected from 50 cassava germplasms, and totally hybridized 10 cross-combinations according to flowering period among different years. Firstly, 134 erect or middle branched candidate lines were screen out through seedling, transplanting and preliminary field trial. Secondly, 13 edible promising lines which aggregated 2-3 target alleles, were chosen by using MATE/PSY2/GBSSⅠ-SNAP markers together. The content of of cyanogenic glucoside in root flesh was determined by spectrophotometry, the value of SC9 was 49.24 μg/g, and those of 13 promising lines were in the range of 38.82-76.51 μg/g; the content of β-carotene in root flesh was determined by acetone colorimetry, the value of SC9 was 184.75 μg/hg, and those of the six yellow-root lines were within the limits of 101.58-154.10 μg/hg; the content of amylopectin in root flesh was determined by dual wavelength spectrophotometry, the values of P13-1 and V7-14, whose alleles were GG that genotyped by GBSSⅠ-SNAP marker, was 82.46% and 83.79%, respectively. Based on this, 5 lines, A5-138, A2-213, P7-6, V4-8 and V4-19, were found to be the potential new edible cassava varieties by taste grading. In conclusion, marker-assisted selection can quickly and accurately screen out the target lines from breeding materials and improve the efficiency of cassava genetic improvement.

Edible cassava is an important food crop in the world and a characteristic potato crop in South China. New edible varieties with high β-carotene and excellent comprehensive quality are one of the important directions of cassava breeding. Manihot esculenta Crantz cv. Gui 9 was obtained from immature fruits, using embryo rescue technology, which were harvested from in-bred crossing population using XX048 as the female. The main characters of the variety were erect plant type, tubers distributed horizontally, cylindrical conical in shape, tubers of light brown skin, pink endothelium and orange flesh. The fresh tuber yield was (45.12±7.04) t/hm² and (40.84±3.88)t/hm² respectively in the regional test and production test. The starch content of fresh tuber detected was 26.3%, β-carotene content was 454 μg/100 g, hydrocyanic acid content was 10-20 mg/kg, tatal sugar content was 2.0 g/100 g, dietary fiber and potassium content was 4.43 g/100 g and 553 mg/100 g respectively. Gui 9 is an edible cassava variety in China with the highest β-carotene content in tuber at present, rich in β-carotene, dietary fiber and minerals, fresh taste crisp and sweet, known as "carrot cassava", with unique advantages in color and taste in cooking and making cassava juice. Gui 9 has high yield and strong adaptability with moderately resistance to cinnabar Tetranychus mites, and is suitable for dense planting and mechanical harvesting. It could be popularized in cassava producing areas such as Guangxi, Guangdong, Hainan and Jiangxi provinces. The breeding of Gui 9 would provide variety support for the development of cassava food, and promote the quality improvement, efficiency increase and sustainable development of cassava industry.

MNP (multiple nucleotide polymorphism, MNP) is a new molecular marker technology emerged with the development of molecular marker technology. While genotyping by target sequencing (GBTS) amplifies only one SNP site in one amplicon, MNP can amplify multiple SNP sites simultaneously in one amplicon based on GBTS. This technology has the features of low cost, high detection efficiency, flexible application and wide adaptability, Compared with SNP, MNP has better ability to differentiate varieties. In order to establish a rapid, accurate and efficient method for cassava variety identification and to screen MNP molecular markers suitable for cassava variety identification, this study screened highly polymorphic regions and designed primers in the whole genome range, and finally obtained 623 cassava MNP marker loci in the whole genome range, the cassava MNP markers were evaluated using 28 cassava varieties. The results showed that the MNP marker typing reproducibility was up to 100%. 4.07±1.68 alleles were detected in 28 cassava varieties, with a maximum of 12 alleles. When all cassava varieties were compared one by a one, 99.47%(376/378) of the differences between pairs were greater than 46%, with the proportion ranging from 0.3% to 81.0%, with a mean value of 71.78%. Meanwhile, MNP markers can be used for identification in the breeding process. In conclusion, the cassava MNP molecular markers developed in this study have high reproducibility, polymorphism and variety differentiation ability, and could be widely used for research on germplasm diversity, new variety breeding and variety identification of cassava.

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.

Using compact varieties SC205, GR4 and umbrella varieties SC12, SC15 as the experimental materials, five treatments of 9, 36, 63, 90 leaves remained and no leaves removed were designed to study the differences of chlorophyll fluorescence and fresh tuber root yield to clarify the differences of chlorophyll fluorescence of functional leaves in different growth stages and leaves remained treatments and the effects of leaves number on fresh tuber root yield. The results showed that with the increase of leaves, the fresh tuber root yield increased, and the tuber root number, the fresh weight of stems and leaves and the harvest index increased first and then decreased. The average of tuber root yield per plant of 9, 36, 63, 90 and no leaf removed treatments was 0.94 kg, 2.22 kg, 2.65 kg, 2.91 kg and 3.35 kg, respectively. The maximum fluorescence yield (F_m) and maximum quantum yield (F_v/F_m) of compact varieties were higher than those of umbrella varieties. F_m and F_v/F_m of compact varieties was 0.885 and 0.739, respectively, and those of umbrella varieties was 0.838 and 0.707, respectively. The minimum fluorescence yield (F₀) of compact type was smaller than that of umbrella type, and that for the two plant type varieties was 0.219 and 0.231, respectively. F₀, F_m, F_v/F_m, ETR and Y(Ⅱ) decreased with the progress of leaf removed. With the increase of PAR, ETR increased gradually, and Y(Ⅱ) decreased sharply first and then slowly. The variation trend of chlorophyll fluorescence of cassava varieties with different plant types was the same, but the variation rule of different leaves was different. The ETR and Y(Ⅱ) of cassava functional leaves increased slightly when the number of leaves remained was small.

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.

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.

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.

In order to understand the diversity of phenotypic traits in F₁ segregation populations of date palm, this study used 143 F₁ segregation populations of date palms as test materials to analyze the diversity, correlation, principal component and cluster analysis of 17 phenotypic traits, including plant height, crown breadth, stem girth, number of branches and leaf spot incidence. The results showed that there was a high degree of phenotypic variation and rich diversity in F₁ segregation population of date palms. The variation degree of quantitative characters was high, the coefficient of variation ranged from 10.927% to 43.350%, and the coefficient of variation of stem girth was the largest. The coefficients of variation of quality traits ranged from 31.447% to 44.619%, among which the coefficients of variation of tiller leaf color and leaf hardness were 44.619% and 42.571%, respectively. The correlation analysis showed that plant height, crown breadth, stem girth, number of branches, the third branch of long, the thorn area length, the total number of tiller leaves, tiller leaves length, tiller leaves width, tiller leaf thickness and leaf color were positively correlated with each other. The incidence of leaf spot was negatively correlated with the other 16 traits. The principal component analysis showed that the cumulative contribution rate of the six principal components reached 87.51%, of which the characteristic value of the first principal component was 10.0836, and the contribution rate was 59.32%. It is mainly affected by the five indicators of plant height, third branch length, crown breadth, stem girth and branch number. The characteristic value of plant height is the largest, which is 0.2948, which mainly reflects the height and growth trend of date palm. The cluster analysis showed that the 143 F₁ generation dates could be divided into five groups: Group Ⅰ included 33 dates with the smallest crown, the least number of branches, the shortest tiller leaves length, and the highest incidence of leaf spot disease. Group Ⅱ included 39 dates resources with the shortest plant height, the smallest stem girth, the shortest third branch length, and the heaviest incidence of leaf spot disease. Group Ⅲ included 23 dates resources with longer tiller leaves, darker tiller leaves, erect plant type and mild incidence of leaf spot disease. Group Ⅳ included 33 dates resources with excellent phenotypic traits such as large ratio of leaf length to width of tiller leaves, stiffer tiller leaves and the least incidence of leaf spot disease. Group Ⅴ included 14 dates resources with small ratio of tiller leaves length to width ratio and open plant type. The results of this study can provide a theoretical basis for the breeding of superior parental traits in later stage of date palm.

Anoectochilus roburghii is a rare and endangered medicinal orchid with high economic value. High temperature is the primary limiting factor for its extensive production and cultivation. Breeding heat-resistant varieties is one of the most economical and effective measures to resist heat damage caused by high temperature. In this study, we analyzed the genetic diversity of 24 A. roburghii germplasm resources by Start codon targeted polymorphism (SCoT) molecular markers, and evaluated the heat tolerance of 20 samples by multivariate statistical analysis. The results of genetic diversity analysis showed that at the genetic coefficient was 0.602, A. roburghii germplasm could be divided into two groups: I and II, Group I was divided into two subgroups A and B, Anoectochilus formosanus was classifiedd into Group II alone. In subgroup A, except W from Yunnan, all the other resources were collected in the north and west of Fujian. Subgroup B mainly came from Southern Fujian and Guangxi. The cluster diagram showed that the relatives of A. roburghii from the same origin was close, and the presence or absence of reticulated veins was not the basis for the classification. Five physiological parameters were measured in the 20 samples. It was found that the chlorophyll content and SOD activity decreased obviously after heat treatment, and the relative conductance increased obviously, while the malondialdehyde and soluble protein contents of each resource were different after heat treatment. The preliminary evaluation of heat resistance was conducted by the multivariate statistical analysis method, and the results showed that four resources (TL, L1, A20, GZ1) were heat resistant, while five resources (TJ, HX, L, M, A21) were not.

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.

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.

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.

To study the differences in the physical and chemical properties of biochar obtained from three legumes at different temperatures, and to determine the appropriate temperature range for legume biochar. Using leguminous plant peanut straw, soybean straw and stylofoam as raw materials, peanut straw biochar (Pe), soybean straw biochar (Be) and stylofoam biochar (St) were prepared at 300 ℃, 500 ℃ and 700 ℃. A Fourier infrared spectrometer was used to qualitatively analyze the functional groups on the surface of the biochar, and the surface morphology of the biochar was observed with a scanning electron microscope, and the physical and chemical properties, such as pH, C and N content, were measured. The results showed that the carbon content of biochar prepared from three kinds of raw materials increased with the increase of pyrolysis temperature at 300 ℃ to 500 ℃, and was basically stable after 500 ℃; the nitrogen content and yield of biochar decreased with the increase of temperature. Among the biomass charcoal prepared from the three materials, Be has the highest carbon content and C/N, and N content and yield are the lowest. The ash content, ash alkalinity and pH of biochar all increase with the increase of pyrolysis temperature. The same pyrolysis ash alkalinity and pH of biochar all increase with the increase of pyrolysis temperature. The same pyrolysis temperature and different materials are all expressed as Be>St>Pe. Both the pore size and specific surface area of biochar increase with increasing temperature. The three raw materials of biochar form more stable aromatic compounds with increasing temperature, and the structure is mainly C=O and C=C. In this study, the suitable pyrolysis temperature of legume biochar is 500 ℃, and the temperature rises again, which has little effect on the physical and chemical properties of biochar. In summary, the soybean biochar produced by cracking at 500 ℃ is more used in farmland soil improvement, and can also try soil remediation, carbon sequestration and emission reduction applications.

The study of crop spatial pattern has important theoretical and practical significance, and has become the frontier and hotspot of geography and ecology. This paper systematically summarized the current progress of allocation method, driving force analysis and simulation of crop spatial pattern. And in this paper, a mind map of research work is presented based on the discussion of the deficiencies and the trends in the study of crop spatial pattern. It is showed that the methods of statistical investigation, remote sensing and spatial model have their advantages and disadvantages in the work of crop spatial information allocation. And it is difficult to fully understand the process of crop spatial pattern change only from the perspective of natural driving force or socio-economic driving force in the work of driving force analysis and simulation of crop spatial pattern. It is suggested that the spatial information comprehensive allocation technology based on spatial model, the multi-factor and multi-scale driving force analysis method combining natural and socio-economic factors, and the simulation model coupling geographical model and socio-economic model will be the important development directions in the field of crop spatial pattern research.

Rubber tree (Hevea brasiliensis) is the only renewable resource among the four major industrial raw materials. The rubber tree anthracnose which infected by the Colletotrichum sp. is one of the most serious foliar disease of rubber production in China. In this study, we investigated the main rubber tree varieties (strains) and monitoring the occurrence and prevalence of anthracnose in Hainan province. It was found that PR107 and RRIM600 had the largest planting area, accounting for 51.06% (102 000 hm²) and 43.39% (86 700 hm²) respectively. The anthracnose of mature rubber plantations and value-added nurseries in Yangjiang Farm was occurred all year round, with the peak period from March to April; Therefore, the rubber tree planted in Hainan province was large, and the variety (strain) was single, so it was easy to break out and spread when the anthracnose was suitable. HCkHNQZ1736 isolated from the leaves of the rubber nursery of Yangjiang Farm in Qiongzhong County, was identified as a new strain of Colletotrichum karstii, which had highly pathogenic to four main varieties of rubber tree, PR107, RRIM600, Reyan 7-33-97 and Dafeng 95. Studied on the results of carbendazim and prochloraz-manganese sensitivity test of HCkHNQZ1736 and MeCkYN1705 showed that the two strains had no resistance to prochloraz-manganese, while the EC₅₀ was 0.0784 μg/mL and 0.0775 μg/mL respectively. However, HCkHNQZ1736 showed high resistance to carbendazim, at this time, the EC₅₀ was 1107.2654 μg/mL, while MeCkYN1705 had only 0.0554 μg/mL.

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.

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.