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).

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.

Two new records and one mainland new record of Dematiaceous hyphomycetes from China, Beltraniella fertilis Heredia, R.M. Arias, M. Reyes & R.F. Castañeda, Subulispora cylindrospora P.M. Kirk and Subulispora procurvata Tubaki wre reported. The specimens were collected from Kuankuoshui National Nature Reserve and Xishui National Nature Reserve of Guizhou. Morphological description, figures were provided for each species, ITS and LSU sequence were provided for B. fertilis and S. procurvata. The specimens are deposited in the Mycological Herbarium of Zunyi Normal College (HMZNC).

In order to meet the demand for high-quality leguminous forage varieties in southern livestock production, comprehensive evaluation of the botanical characters of high-quality breeding resources is the premise of breeding. Dendrolobium triangulare is a perennial shrub with large leaves, high yield and high nutritional value. It is an excellent high-protein green feed. At present, there are only studies on the genetic diversity among the subgroups of the locust, and the analysis and research on the morphological genetic diversity of the genus Desmodium Desv. are relatively scarce, and there is a lack of research on the morphological genetic diversity of germplasm in a large range. In this experiment, a random block design was adopted, and the research materials were 76 germplasm resources of the genus Desmodium Desv. 35 botanical traits were observed, and the genetic diversity characteristics of Desmodium Desv spp. were analyzed for future breeding work of Desmodium Desv. Provide basic materials. The genetic diversity was studied by morphological observational analysis. The 35 botanical traits, the hair condition on the back of the leaf (CV=46.92%), the color of the stem (CV=39.77%) and the condition of the petiole hair (CV=39.52%) had the largest coefficients of variation, indicating that the false D. triangulare. was rich in genetic diversity. There were correlations among several botanical characters, there was a very significant positive correlation between leaf length and leaf width (r=0.887), the aspect ratio was about 2.0, and the leaf shape was close to ellipse. There was a correlation between the shape of the stem and the length of the leaf (r=-0.459) and the width of the leaf (r=-0.491), indicating that if the yield of pseudo pigeon is mainly based on the leaf area, the cylindrical stem should be selected as much as possible. There was a very significant correlation between the leaf shape of the central leaflet and the length of the pod (r=0.360), so the selection of obovate leaves during breeding could improve the seed yield. There was a very significant correlation between the hair condition on the back of the leaf, the hair condition on the petiole (r=0.462) and the hair condition on the pod (r=0.589), indicating that the hair coat condition of the same plant has a high correlation, and the resources with less hair coat on the whole plant can be screened. Through cluster analysis and systematic evaluation, four germplasm resources were screened out (D. triangulare 070314022, D. triangulare GX121121004, D. triangulare 050218087, D. triangulare 050307492), and the germplasm resources had the characteristics of high yield and high quality. This experiment explored the characteristics of genetic diversity of botanical traits among the species of D. triangulare, which could provide basic materials for subsequent breeding work.

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 this study, 100 matreials of innovative germplasm from Yunnan octoploid Saccharum spontaneum L. 84-268 bloodline F₂ population were used as materials, and 7 main agronomic factors including plant height, stalk diameter, brix, effective stalk number, single stalk weight, cane yield and sugar yield were measured, and frequency distribution histogram analysis, coefficient of variation analysis, correlation analysis, principal component analysis and cluster analysis were done. The results showed that the data of the 7 agronomic traits presented a good normal distribution and abundant variation with the variation coefficient ranging from 9.91% to 50.76%, and the maximum variation coefficient of sugar yield was 50.76%. Correlation analysis and stepwise regression analysis showed that the cane yield was significantly and positively correlated with plant height, stalk diameter and effective stalk number, having a determination coefficient of 0.9282. The sugar yield was mainly determined by plant height, stalk diameter, brix, single stalk weight and effective stalk number, and the coefficient of determination was 0.9160. The seven agronomic traits were integrated into three main components by principal component analysis, and the cumulative contribution rate was 86.985%. The first principal component, cane yield and sugar factor, was the most important factor, which contributing rate was 47.615%. At the Euclidean distance of 6.00, the 100 innovative materials were divided into 3 categories, and the results were consistent with the principal component scoring. The 7 traits were excellent in group Ⅰ, and a total of 15 high-quality materials were screened out, which had a high principal component score. In particular, it was worth of paying high attention to YGF₂18-226-7, YGF₂18-226-14, YGF₂18-226-89, YGF₂18-226-48, YGF₂18-226-96, YGF₂18-226-21, YGF₂18-226-43 and YGF₂18-226-5. These materials can be further screened as the parents or reserved as core germplasm for breeding research.

Low temperature is an important factor limiting the growth, development and yield of pitaya. 2,4-Epibrassinolide (EBR) can enhance the resistance of plants to various stresses such as low temperature. In order to improve the cold resistance of pitaya and alleviate the damage caused by low temperature, the cutting seedlings of red pulp pitaya 'Taiwan No. 6' was sprayed with 0.5 mg/L EBR, and treated under low temperature stress (4℃/0℃, 12 h/12 h) for 7 days. Reactive oxygen species (ROS) content, antioxidant enzyme activity, relative conductivity (REC), malondialdehyde (MDA) content, fatty acid composition and content were determined to clarify the regulatory effect of EBR on the cold tolerance of pitaya seedlings. Furthermore, the relationship between antioxidant system and fatty acid unsaturation of membrane lipids under low temperature stress was studied. Low temperature stress (4℃/0℃, 12 h/12 h) increased the content of reactive oxygen species (ROS), significantly decreased the content of unsaturated fatty acids. The fatty acids unsaturation (UFA/SFA) and double bond index (DBI) reduced by 32.1% and 32.4% respectively, and significantly increased the content of malondialdehyde (MDA) and relative conductivity (REC), resulting in decreased membrane stability and increased membrane permeability. The plants showed obvious watery stains and slight wilting, and the index of chilling injury reached 0.60. Under low temperature, exogenous EBR treatment increased the activities of superoxide dismutase, peroxidase and catalase, effectively removed the excessive accumulated ROS, significantly reduced the production rate of superoxide anion and the content of hydrogen peroxide, alleviated the oxidation reaction between ROS and unsaturated fatty acids in membrane lipids, and increased the relative content of unsaturated fatty acids in pitaya seedlings. The proportion of saturated fatty acids decreased significantly, UFA/SFA and DBI increased significantly, EBR maintained the stability of cell membrane, reduced REC and the content of membrane lipid peroxidation products MDA, greatly reduced watery stains of plants, and the index of chilling injury was reduced to 0.25. It is becouse EBR can activate the antioxidant enzyme system and effectively remove a large number of accumulated ROS under stress, leading to reduce the double-bond fracture of unsaturated fatty acids in membrane lipids, alleviate the degree of membrane lipid peroxidation, maintain the stability and function of membrane membrane. In conclusion, under low temperature stress, exogenous EBR can effectively improve the cold tolerance of pitaya seedlings. Its mechanism is by increasing the activity of antioxidant enzymes in pitaya seedlings, remove excess accumulated ROS, and significantly increase the unsaturation of cell membrane fatty acids, so as to reduce the degree of membrane lipid peroxidation and electrolyte leakage, maintain the stability and function of cell membranes.

The elucidation of cucurbitacin biosynthesis pathway is essential for heterologous production due to its significant anticancer activity. The biosynthesis of cucurbitacin starts from cucurbitadienol (Cuol) catalyzed by cucurbitadienol synthase (CBS) of the oxysqualene cyclase (OSCs) family to form 2,3-oxysqualene which subsequently catalyzed by cytochrome P450 (CYP) and other enzymes for oxidative modification to produce various cucurbitacins. In this study, an efficient transient expression system mediated by Agrobacterium tumefaciens was established. The CBS gene (HcOSC6) from Hemsleya chinensis and truncated 3-hydroxy-3-methyl-glutaryl coenzyme A reductase gene (tHMGR) from Avena strigose were continuously optimized in the tobacco co-expression system to increase Cuol yield from 2.832 mg/g (DW) to 9.48 mg/g (DW) in Nicotiana benthamiana leaves. Meanwhile, HcCYP87D20 of H. chinensis was also co-infiltrated into tobacco leaves to obtain 11-carbonyl-20β-hydroxy-cucurbitol. This study would provide a theoretical basis for efficient heterologous production of cucurbitacin.

The effects of phosphorus (P) and lime application on yield and biomass and P uptake and utilization of sweet corn were evaluated with a field experiment. Research on the appropriate rate of P application would provide a theoretical basis in improving sweet corn yield and P use efficiency. The field experiment was a split-plot design with main-plot randomly assigned into each of four blocks. The main-plot treatments were four P application rates (0, 60, 120 and 180 kg/hm², expressed as P₀, P₆₀, P₁₂₀ and P₁₈₀). The split-plot factors were two lime levels (0 and 750 kg/hm², expressed as L₀ and L₁). The responses of sweet corn yield, P uptake, soil available P and P fertilizer utilization efficiency to P fertilizer application and lime application were studied. The yield of sweet corn increased significantly under P₁20 and P₁₈₀ treatments without lime by 19.4% and 18.5%, respectively, compared with P₀ treatment. Compared to P₀, the yield of sweet corn increased significantly by 14.0% under P₆₀ treatment with lime. Under P₆₀ treatment, lime increased the yield of sweet corn significantly by 12.7%. P fertilizer application increased both total biomass and P uptake of sweet corn significantly. After two sweet corn growing seasons, soil available P under P₆₀ treatment had no significant difference comparing with the original value. Soil available P basically maintained a balance under P₆₀ treatment. Soil available P in P₁₂₀ and P₁₈₀ treatments increased by 103.8% and 228.4%, respectively, compared with the original value, and soil available P increased obviously in 0-20 cm soil layer. The fresh ear yield per P uptake and P physiological efficiency decreased significantly with P application rates. Also, the P use efficiency of sweet corn declined with P application rates. P agronomic efficiency, recovery efficiency, and partial factor productivity increased significantly under lime treatments with P₆₀ treatment, compared with no-lime treatments. Together, these results indicated that the application of 60 kg/hm² P fertilizer combined with lime can be an efficient way to obtain high yield and P utilization efficiency of sweet corn and maintain the balance of soil available P.