Streptomyces acidiscabies (SA), Ralstonia solanacearum (RS) and Erwinia carotovora subsp carotovora borgey (ECCB) cause plant scab, brucellosis and soft rot of carrot, respectively. These are common and prevalent bacterial disease in crop production. The volatile oil of Guava leaves consists of a variety of active substances with broad-spectrum anti-microbial activity. The aim of this study was to extract and configure an antimicrobial solution of guava leaves volatile oil to conduct a volatile oil resistance study against three disease bacteria, SA, RS and ECCB, to reserve resources for biological control agents. The volatile oil of guava leaves was extracted by the addition of lithium salt combined with microwave-assisted hydrodistillation, the antibacterial effect of guava leaf volatile oil on three test strains was evaluated by the filter paper diffusion method and minimum inhibitory concentration (MIC), and the extraction process was optimized by single factor combined with response surface experiments. The chemical components of guava leaf volatile oil were determined by gas chromatography-mass spectrometry (GC-MS). The results showed that the oil exhibited excellent inhibitory effects against SA, RS and ECCB, with the inhibition circle diameters ranging from 20.57 to 23.24 mm and the inhibition rates reaching more than 60%, and the MIC values of 3.13 μg/mL, 1.56 μg/mL and 3.13 μg/mL, respectively. The oil had the greatest inhibitory effect on RS, the diameter of the inhibition circle was (23.24±0.47)mm, which was highly sensitive, and also had certain inhibitory effect on SA and ECCB. The optimum process conditions for the extraction process were liquid to material ratio of 10 mL/g DW, microwave power of 660 W and microwave time of 43 min. The yield of the oil obtained under the conditions was (10.23±0.17)mL/kg DW, and the validity and reproducibility of the method were verified by three parallel experiments. The components of the oil were detected to be mainly terpenes and alcohols, with relatively high content of β-caryophyllene (28.36%), l-calamenene (11.47%), (-)-globulol (11.31%) and α-pinene (10.01%). The substances that played a major role in the antibacterial experiment were β-caryophyllene, α-pinene, eugenol, and D-limonene. It was speculated that the mechanism of guava leaf volatile oil inhibition on the test strain was the damage to its cell structure, which resulting in the leakage of intracellular material. The above results demonstrated that the guava leaf volatile oil has an excellent antimicrobial activity and considerable extraction rate, the results of the study would provide a reference for the development and application of guava leaves and integrated control of crop diseases.

Chilling injury during tobacco seedling stage is an important problem affecting tobacco agricultural production, and enhancement of the chilling resistance by various agronomic measures has practical significance. In this study, using two main cultivars Yunyan97 and K326 as the experimental materials, the seedlings were pretreated with salicylic acid (SA) at concentrations 0, 0.5, 1.0 and 1.5 mmol/L. Then the pretreated seedlings were transferred to 10℃ for 12 days for chilling treatment. Compared with the control without SA pretreatment, the SA pretreatment could significantly reduce the malondialdehyde (MDA) content and ratio of electrolyte leakage, slowed down the consumed rate of dry matter, increased chlorophyll content and root vigor, improve root length, surface area, volume and number of roots, promoted the growth of root system under the chilling stress, and finally enhanced the chilling resistance of 'Yunyan 97' and 'K326' seedlings. The optimum SA concentration of different tobacco varieties varied, that for 'Yunyan 97' and 'K326' was 1.5 mmol/L and 1.0 mmol/L respectively. After the SA pretreatment, the content of reduced ascorbic acid (ASA) and glutathione (GSH) in the antioxidant defense system in the seedlings remained a higher level, but oxidized ASA and GSH maintained a lower level, and ratio of the reduced antioxidants in total antioxidants increased. Ascorbate peroxidase (APX), catalase (CAT), guaiacol peroxidase (GPX), glutathione reductase (GR) and superoxide dismutase (SOD) maintained high activities compared with the control before and during the chilling treatment. The results indicated that after the SA pretreatment, the seedlings could maintain higher reduced antioxidant level and antioxidant enzyme activity, and remain higher antioxidant capacity, which would lay an important biochemical foundation for SA-induced chilling resistance in tobacco seedlings. The results would not only have reference significance for raising chilling-resistant tobacco seedlings, but also referential value for culture of seedlings and early cultivation of other crops and vegetables.

Cassava is an important cash crop in Southern China, which is enriched with starch in the tuber roots. The analysis of the regulation mechanism of starch synthesis in cassava root would contribute to the improvement of yield and high starch molecular in cassava. AGPase is composed of large subunit and small subunit, and it catalyzes G-1-P and ATP to form ADPG and PPi, in which ADPG is the substrate of starch biosynthesis. Therefore, AGPase is a rate-limiting enzyme in plant starch synthesis, and improving the activity of AGPase is beneficial for the accumulation of crop starch and the improvement of yield. The small subunit encoded by MeAGPS1a is the catalytic center of AGPase in cassava. Previous studies have shown that the growth response factor MeSAUR1 as a transcription factor positively regulates the expression of MeAGPS1a gene, and yeast two-hybrid screening of a cassava cDNA library revealed that the calmodulin-like (CML) member MeCML24 is a candidate interacting protein of MeSAUR1. To determine the interaction between MeCML24 and MeSAUR1, and MeCML24 was cloned from the genome of SC8 cassava variety in this study. The length of CDS region of MeCML24 was 492 bp, encoding 163 amino acids. The physicochemical properties and secondary structure analysis of MeCML24 showed that the value of theoretical pI was 4.38, which belonging to hydrophilic protein with α-helix accounting for 52.76%, random coil accounting for 30.06%, and beta turn accounting for 11.04%. Yeast two-hybrid vector BD-MeCML24 was constructed, and the self-activation experiment showed that MeCML24 had no self-activation. Yeast two-hybrid point-to-point experiment revealed that yeast strains co-transfected with AD-MeSAUR1 and BD-MeCML24 plasmids turned blue on nutrient medium with SD/TLHA+x-α-gal, indicating that MeCML24 interacted with MeSAUR1. The fusion protein MeSAUR1-nEYFP and MeCML24-cEYFP were co-expressed in tobacco leaves by bimolecular fluorescence complementation (BiFC) experiment, and the fluorescence signal of yellow fluorescent protein EYFP was detected under laser confocal microscope, which further proved the interaction between MeCML24 and MeSAUR1. Finally, the interaction between MeCML24 and MeSAUR1 negatively regulated the expression of MeAGPS1a by double luciferase experiment. The study revealed the mechanism of MeSAUR1 and MeCML24 synergistically regulating MeAGPS1a gene expression in cassava, and found that the calmodulin-like protein MeCML24 regulating the expression of MeAGPS1a, a key gene for starch synthesis in cassava root. This study would provide a theoretical basis for cultivating excellent cassava varieties by molecular biology technology.

Passion fruit (Passiflora edulia Sims), as an emerging tropical fruit tree, plays a very important role in tropical agriculture. However, abiotic stresses such as drought and high temperature seriously affect its normal growth and development. Relevant studies have shown that aquaporin (AQP) can improve the stress resistance of plants. In this study, Passiflora 'Tainong' was used as the material, an aquaporin gene PePIP2 was cloned using the genome data of passion fruit. The open reading frame (ORF) was 861 bp, encoding 286 amino acids. The molecular formula was C₁₄₁₇H₂₁₅₆N₃₆₀O₃₇₃S₈, the molecular weight was 30 459.37 Da, the isoelectric point was 8.84, and the subcellular localization was on the cell membrane. Analysis of the promoter region revealed that it contained cis-acting elements involved in stress response. The expression analysis showed that PePIP2 could be induced by drought, high temperature and low temperature stress. Among them, the expression level was the highest when the soil water content was 50%, treated at 45℃ for 4 h and at 0℃ for 48 h. Transiently expressed in tobacco, the expression of PePIP2 was also induced to varying degrees under drought stress at different times. The results of this study would lay the foundation for the analysis of the stress resistance mechanism and molecular breeding of the passion fruit.

Tigernut (Cyperus esculentus L.) is a perennial herb that is native to Africa and the Mediterranean coast. Due to the shortage of edible vegetable oil and biodiesel in China, tigernut has been emerging as a promising oil crop for its wide adaptability and high oil production per unit. To promote the development and utilization of this special crop, EPSPS (5-enolpyruvylshikimate-3-phosphate synthase) genes, which encode a key enzyme targeted by herbicide glyphosate in the shikimate pathway for the synthesis of aromatic amino acids, were identified from tigernut as well as several representative monocots based on genome and transcriptome data available. Comparative analyses revealed that (a) tigernut harbors a single EPSPS gene (denoted CeEPSPS) with seven introns as observed in most plant species; (b) its complete coding sequence of 1584 bp was further isolated using RT-PCR; (c) among 514 amino acids encoded by CeEPSPS, the first 70 residues from the N-terminal were characterized as the chloroplast signal peptide, whereas the peptide from sites 77 to 508 belongs to the highly conserved EPSP_ synthase domain (under the Pfam accession number of PF00275); (d) compared with the EPSP_ synthase domain, the chloroplast signal peptide is relatively more variable; and (e) the maturation protein of CeEPSPS was predicted to possess the theoretical molecular weight (Mw) of 47.32 kDa, the isolectric point (pI) of 5.49, the grand average of hydropathicity (GRAVY) of 0.069, the aliphatic index (AI) of 93.76, and the instability index (II) of 31.73, which is similar to other reported EPSPSs and could be categorized as a type of hydrophilic, acidic, and stable proteins; (f) phylogenetic analysis using deduced EPSPS proteins supports that tigernut is a Cyperaceae plant within Poales. Further sequence alignment and genome resequencing analyses revealed that no target site resistance mutations to glyphosate were found in all 56 germplasms investigated in this study. Gene expression analysis using qRT-PCR showed that CeEPSPS was dominantly expressed in mature leaves and tubers, which were significantly higher than that in buds, young leaves, senescent leaves, and rhizomes. Additionally, a plant vector of over-expressing CeEPSPS was also constructed, which would lay a solid foundation for the following molecular breeding for glyphosate resistant in tigernut and other species.

In order to determine the quality of soil fertility of bamboo species in coastal sandy land and guide the construction and management of bamboo shelter forest in coastal sandy land, the difference of soil physical and chemical properties of different bamboo forests in coastal sandy land and evaluate the soil quality were studied. Eight bamboo species in coastal sandy land were selected from Chishan State-owned Farm in Dongshan County, Fujian Province. The physical and chemical properties of the 0-20 cm soil layer of each bamboo species were determined. One-way ANOVA analysis was conducted to test the significance of each index, and principal component analysis weighted comprehensive index method and fuzzy mathematics were used to comprehensively evaluate the soil fertility quality of different bamboo species. Soil moisture content, soil density, capillary porosity, non-capillary porosity and total soil porosity of Oligostachyum lubricum were significantly different from those of other bamboo forest (P<0.05). The average pH of soil ranged from 5.01 to 7.36, and there was no significant difference in the pH of other bamboo forests except the neutral soil pH of Bambusa oldhamii (P>0.05). The average soil organic from 4.43-11.06 g/kg, Pseudosasa amabilis var. convexa was significantly lower than that of other bamboo forests. The average range of soil total potassium and available potassium was 4.59-79.33 g/kg and 0.78-43.11 mg/kg. The average range of soil total nitrogen and total phosphorus was 0.47-2.42 g/kg and 0.09-0.37 g/kg, and soil electrical conductivity, total availability and quick availability of N, P, K. had significant differences among different bamboo forests (P<0.05). The order of soil fertility quality index order of the eight bamboo species was P. japonica>O. lubricum>Phyllostachys nidularia f. farcata>B. oldhamii>Dendrocalamus minor var. amoenus>B. tuldoides 'Swollenintrnode'>B. eutuldoides var. viridi-vittata>P. amabilis var. convexa. The physical and chemical properties and total soil quality of bamboo shelterbelt in coastal sandy land were significantly affected by the types of bamboo stands. P. japonica could effectively improve soil quality, but the effect of P. amabilis var. convexa. on soil improvement was not obvious. Bamboo species and planting methods should be selected rationally for the construction and management of bamboo shelterbelt in coastal sandy land.

Cassava is an important food crop in tropical regions. Cassava bacterial blight caused by Xanthomonas phoseoli pv. manihotis (Xpm) is an important disease of cassava. Excavating and identifying the genes of cassava resistance to Xpm and analyzing its disease resistance mechanism are beneficial to the development of cassava disease-resistant germplasm. Plant heat shock transcription factors (Hsfs) play an important role in the process of plants resisting biotic and abiotic stresses. In this study, the full-length heat shock protein transcription factor gene MeHsfB3a was cloned from cassava cultivar 'Huanan 8' ('SC8') by RT-PCR technology. Bioinformatics analysis found that MeHsfB3a contained two exons and one intron, with a full length of 729 bp, encoding 242 amino acids with 27.9 kDa and pI=7.59. The theoretical instability coefficient was 56.86, which is an unstable protein, and the average hydrophilicity index was-0.880, indicating that the protein has good water solubility, and the fat solubility index was 65.98. The protein was predicted to localize in the nucleus. qRT-PCR analysis found that MeHsfB3a was expressed in young leaves, mature leaves, terminal buds, petioles, tuberous roots and fibrous roots, with the highest expression in mature leaves and less in other organs. The expression of MeHsfB3a was analyzed after 0 h, 3 h, 6 h, 1 d, 3 d and 6 d after infection of cassava 'SC8' leaves by pathogen XpmHN11, and it was found that the expression of this gene was significantly increased after 1 d. This indicated that MeHsfB3a was involved in the response of 'SC8' cassava to XpmHN11. The MeHsfB3a gene of cassava 'SC8' was silenced by the VIGS technology, and the gene silencing efficiency reached 68.26%-82.44%. The leaves of silent plants were inoculated with XpmHN11, and the disease incidence was analyzed on 0 d, 3 d, and 6 d of inoculation, and it was found that the area of disease spots of the silent plants was significantly higher than that of the control. This study identified the heat shock protein transcription factor gene MeHsfB3a involved in the process of cassava resistance to XpmHN11, which would help to further analyze the disease resistance mechanism of cassava to cassava bacterial blight.

This article aims to study the differences in the photosynthetic characteristics of different tea cultivars. The photosynthetic parameters in the leaves of nine tea cultivars were determined under field conditions, and the light response curves were drawn. The photosynthetic indicators of different tea cultivars were comprehensively evaluated by statistical analysis, principal component analysis, cluster, discrimination analysis and correlation analysis. There were great differences in net photosynthesis rate (P_n), transpiration rate (T_r), stomatal conductance (G_s), intercellular CO₂ concentration (C_i). Among them, P_n, T_r of 'Yunshan' and 'Yunkang 10^#' were significantly higher than those of the other tea cultivars (P<0.05), G_s of 'Tian', 'Baohong' and 'Shilixiang' was significantly lower than that of the other tea cultivars (P<0.05), C_i of 'Changningdayezhong' was significantly lower than that of the other tea cultivars (P<0.05). At the beginning of photosynthetically active radiation (PAR), differences in the P_n between tea cultivars were not distinct. However, with the increase in PAR, great differences in P_n between tea cultivars appeared. The G_s and T_r of the nine tea cultivars showed two trends with the increase of PAR, 'Xiangguiyinhao' showing a first upward and then trend till to be stable, while other tea cultivars showing an overall upward trend. The C_i of the nine tea cultivars decreased rapidly at first and then tended to be stable. The WUE and iWUE increased first and then decreased with the increase of PAR, and the ability to tolerance of strong drought for 'Changningdayezhong' and 'Xiangguiyinhao' was better than that of the other tea cultivars with a higher WUE and iWUE, and both of them could be used as the drought tolerance tea cultivars suitable for breeding needs. The photosynthetic potential for 'Yunkang 10^#', 'Xiangguiyinhao', 'Yunashan' was better than the other tea cultivars with a higher P_nmax, and they could be used as the high-light-efficiency tea cultivars suitable for breeding needs. The LSP of 'Shilixiang', 'Changningdayezhong' and 'Zijuan' was significantly higher than that of other tea cultivars (P<0.05), and had a strong ability to use strong light. The strong ability to use low light for 'Xiangguiyinhao' and 'Shilixiang' was better than that of the other tea cultivars with a lower LCP (P<0.05). The nine tea cultivars were divided into four groups by principal components and cluster analysis. Correlation analysis indicated that P_n was significantly positively correlated with G_s and T_r (P<0.01).

In this paper, a 3-factor fertilization experiment with N, P and K in an incomplete orthogonal design of "3414" was conducted to validate the optimal fertilization effect model, and the dry weight of single fruit and hesperidin content of Citrus medica 'Fingered' (CM) were used as the indicators for statistical analysis. The results showed that nitrogen, phosphorus and potassium fertilizers had effects on the dry weight of single fruit and hesperidin content in CM and N₂P₂K₂ (40g/plant for N, 40g/plant for P and 45g/plant for K) had the best effect among the different fertilization treatments, and no or less fertilization led to the decrease of quality of CM in Wanzhou to different degrees. The two-factor interaction analysis showed that when any of the N, P and K fertilizers were at the level of 2, with the increase of the other two factors, the single fruit dry weight and hesperidin content of CM showed a trend of increasing and then decreasing, indicating that any two factors interacted with each other within a certain range, and two of the N, P and K factors had an interaction effect. The optimization results of the fertilization model indicated that the suitable fertilization rates of N, P and K for cultivation of CM in Wanzhou ranged from 38.78 g to 51.25 g per plant, 35.67 g to 42.35 g per plant and 48.17 g to 60.37 g per plant, respectively. The results of the validation experiments under the intermediate conditions of the optimal fertilizer application effect model showed that the dry weight yield of single fruit of CM was 8.14% higher than that of the highest group of "3414", and the hesperidin content was 1.94% higher than that of the highest group of "3414". This indicates that the optimal formulation fertilization model is reasonable which has some practical guidance for the field cultivation of C. Sarcodactylis Fructus.

To investigate the effects of different coating treatments on the quality of betel nut fresh fruits during storage, three groups of coating agents, aseptic distilled water (CK), chitosan (T₁), and chitosan-chitosan-thymol (T₂), were used to coat the surface of betel nut fresh fruits and then packed in PE bags with perforations to determine the quality changes of fresh fruits stored at 13℃ and 65% relative humidity for 40 days. The results showed that the T₁ and T₂ film treatments effectively delayed and inhibited fruit decay and softening, kernel browning, yellowing, water loss and shrinkage, and extended the shelf life from 5 days to 35 days. Compared with the CK group, the T₁ treatment effectively inhibited fruit yellowing, but the T₂ treatment had the best overall preservation effect, which not only enhanced the initial antioxidant capacity of fresh fruits, but also significantly inhibited the increase of weight loss and decay rate, and the decay rate was only 8% at the 35th day. At the same time, the color of fresh fruits was more stable and the browning of kernels was not obvious in T₂ treatment. In addition, the changes of respiratory intensity, hardness, cellulose and lignin content had showed that the T₂ coating treatment could maintain the physiological and metabolic capacity of fresh fruits during the storage period after 25 days, and the freshness preservation effect was significantly better than that of the CK group, so the T₂ coating treatment can be used as a green, safe, economic and effective method to preserve fresh fruits of betel nut.