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 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.

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.

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.

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.

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.

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.

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.

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.