Abstract:【Objective】To express the capsid protein (Cap) of porcine circovirus type 2 (PCV2) in insect cells and analyze the immunogenicity of recombinant protein.【Method】The established recombinant bacmid containing fused ORF2 gene (Bacmid-ORF2) was transfected into insect cells for protein expression test, and then the purified *Cap and pcDNA3.1-ORF2 plasmid were immunized mice respectively to compare their immunological effects.【Result】The Cap structural protein encoded by PCV2-ORF2 gene was correctly expressed in insect cells, and the relative molecular mass was about 32 000. *Cap could be recognized by PCV2 positive serum and had good antigenicity. The immue effect of *Cap group was better than that of pcDNA3.1-ORF2 group in both cellular immunity and humoral immunity levels.【Conclusion】The recombinant protein *Cap can replace the whole virus and may have potential application values of PCV2 vaccinum. These results lay the foundation for the study of molecular diagnosis, subunit vaccine development and molecular biology research of PCV2.

Abstract:【Objective】To investigate the antimicrobial resistance of Escherichia coli from diarrhea dogs and the distribution of integron-gene cassettes in E. coli.【Method】The Kirby-Bauer disc diffusion method was used to test the susceptibility of 30 strains of E.coli against 19 antimicrobial agents. PCR was used to detect the integrase genes(class I, Ⅱ, Ⅲ) in E.coli isolates. We further detected if E.coli isolates carrying integrase genes also carried the sul1, qacEΔ1 genes and gene cassettes in variable regions.【Result】Thirty isolates showed different levels of resistance to 19 antimicrobial agents with 18 kinds of resistant spectrum. E.coli isolates had high resistance to amoxicillin, ampicillin, tetracycline and doxycycline with drug resistance rates of 90.00%, 83.33%, 66.67% and 63.33%, respectively, while had low resistance to the other antimicrobials with drug resistance rates below 14.00%. Eleven out of 30 isolates were found to carry class I integrase, sul1 and qacEΔ1 genes, and class Ⅱ or class Ⅲ integrase gene was not detected. Among the isolates carrying class I integrase gene, the dfrA12+orfF+aadA2 gene cassette of 1 879 bp length was successfully amplified from two isolates.【Conclusion】E.coli isolates from diarrhea dogs show different levels of resistance to antimicrobial agents. Antimicrobial resistance that mediated by gene cassettes is partially related to the resistant phenotype of E.coli. Class I integron shows a certain relationship with the antimicrobial resistance of E.coli.

Abstract:【Objective】To analyze the genetic variation of foot-and-mouth disease virus (FMDV) in Guangdong area, and provide fundamental data for studying FMDV infections as well as prevention and control of foot-and-mouth disease.【Method】We amplified and sequenced VP1 and 3A genes of FMDV from pathological samples of pigs in Guangdong area from 2015 to 2016, and analyzed the gene sequences.【Result】Eleven strains of type O FMDV strains belonged to the social spectrum type strains. Seven type A FMDV strains belonged to the Asia type strains. Comparing the VP1 genes of the 11 type O FMDV strains with pandemic strains, GD-MM-3 and O/BY/CHA/2010 strains had the highest sequence similarity being 95.3%, while strain GD-1, GD-MM-1 and GD-MM-3 had the highest sequence similarity of 90.8% compared to strain O/MYA/1/98. Comparing the VP1 genes of 7 type A FMDV strains with pandemic strains, A/GDMM/2013 and GD-CH-3 strains had the highest sequence similarity being 99.8%, while A/HuBWH/2009 and GD-3 strains had the highest sequence similarity being 91.4%. Amino acid deletion was not found in 3A proteins of 11 type O FMDV strains. The 3A proteins of 7 type A FMDV strains had multiple amino acid deletions.【Conclusion】The genetypes of FMDV in part area of Guangdong are complex, which leads to the difficulties of disease prevention and control.

Abstract:【Objective】To investigate the prevalence of porcine reproductive and respiratory syndrome virus (PRRSV) in Guangdong province.【Method】From 2014 to 2016, totally 1 137 porcine tissue samples and 9 432 porcine serum samples were collected from scaled pig farms in Guangdong for antigen and antibody detection respectively. The results were compared among different years, seasons and regions. Phylogenetic analysis were performed on isolated viruses.【Result】From 2014 to 2016, the yearly positive rates of PRRSV antigens were 30.86%, 34.35% and 37.50% respectively, while the yearly antibody positive rates were 82.86%, 68.87% and 74.56% respectively. In quarterly analysis, the first quarter had the highest antigen positive rate of 40.27% and the second quarter had the lowest antigen positive rate of 28.66%. The antibody level of every quarter was above 70%. There were significant differences in PRRSV infection rates among different regions. The infection rates in eastern Guangdong and western Guangdong were significantly lower than those in the Pearl River Delta and northern Guangdong. The antibody positive rate was the lowest (69.51%) in eastern Guangdong and above 75% in the other three regions. A total of 69 PRRSV strains were isolated from samples with positive antigen, of which 39 strains belonged to Subgenotype I.【Conclusion】The antigen positive rate of PRRSV in Guangdong shows an increasing trend, while the antibody positive rate is relatively high but unstable. Subgenotype I is the predominant subgroup in Guangdong based on the virus isolation results.

Abstract:【Objective】To carry out genetic analysis and gene mapping of purple leaf character in the rice material pl41, and provide a foundation for pl41 gene map-based cloning, function research and application in rice breeding.【Method】The genetically stable purple leaf germplasm pl41 was derived from the hybrids of a purple leaf indica cultivar ‘Z3474’ and a green leaf japonica cultivar ‘Nipponbare’. The phenotypic characteristics of pl41 were surveyed. pl41 was crossed with ‘Nipponbare’, then F₁ and F₂ segregation progenies were used for genetic analysis and preliminary mapping of pl41 gene.【Result】The purple character of pl41 firstly appeared in leaf sheath, leaf apex and leaf margin at seedling stage, then the aboveground parts of pl41 plant presented dark purple at heading stage. Compared to ‘Nipponbare’, chlorophyll content of pl41 was significantly higher at seedling stage, significantly lower at heading stage and there was no significant difference at filling stage. Anthocyanin contents of pl41 were all significantly higher than those of ‘Nipponbare’ at seedling, heading and filling stages. The purple leaf character of pl41 was controlled by a pair of recessive nuclear genes, which was mapped to a 289 kb region on the short arm of chromosome 12. By sequencing for coding sequences of five genes within this mapped region, no difference was found in coding sequences of these genes between Pl41 and ‘Nipponbare’.【Conclusion】The region of rice purple leaf gene pl41 is mapped preliminarily. The exact determination of pl41 depends on fine mapping, sequence alignment analysis and transcription analysis of candidate genes.

Abstract:【Objective】To explore efficient induction method of autotetraploid Benincasa hispida and seek a simple, convenient, large flux and accurate method of ploidy level identification.【Method】The seedlings of diploid B. hispida inbred lines were used as materials. Autotetraploid B. hispida was induced using different concentrations of colchicine and oryzalin at different times including 06:00 to 07:00, 12:00 to 13:00 and 17:00 to 18:00 to treat the growth points of seedlings. Ploidy levels of mutated plants were determined by using the methods based on plant morphology, cytology, flow cytometric analysis and chromosome numbers of root tips.【Result】There were certain induction effects by using different concentrations of colchicine and oryzalin at different times, but the induction rate of colchicine was overall higher than that of oryzalin, and the highest induction rate was 32.18% using 2 g·L^–1 colchicine from 06:00 to 07:00. The ploidy identification result from the combination of methods based on plant morphology, cytology and flow cytometric analysis was the same as the result based on chromosome numbers of root tips.【Conclusion】The optimum method of obtaining autotetraploid was using 2 g·L^–1 colchicine from 06:00 to 07:00. The combination of plant morphology, cytology and flow cytometric analysis was a simple, convenient, large flux and accurate way to identify ploidy level.

Abstract:【Objective】To clarify the physiological and ecological mechanisms of ginsenoside biosynthesis, and reveal the relationship between ecdogical/genetic factors and quality of medicinal materials. 【Method】Cultivated four-year-old Panax ginseng leaves at different growth times were used as materials. The contents of eight ginsenosides (Rg₁、Re、Rf、Rb₁、Rb₂、Rb₃、Rc、Rd) in leaves were detected by HPLC. The expression of seven key enzyme genes (HMGR, FPS, SS, SE, DS, β-AS, CYP716A47) involved in ginsenoside biosynthesis in ginseng leaves were determined by real-time quantitative fluorescent PCR. The effect of ecological factors and the expression of key enzyme genes on the synthesis and accumulation of ginsenosides in P. ginseng leaves were investigated by correlation and grey relational analysis.【Result】The expression of key enzyme genes involved in ginsenoside synthesis was active from July 13th to September 29th, and the expression of different genes synergistically increased or decreased. The contents of ginsenoside Re and Rg₁ in P. ginseng leaves were the highest, reached the maximum of 60.30 and 39.38 mg·g^–1 respectively in the growth period of ginseng root from August 31st to September 13th. Temperature, photosynthetic active radiation (PAR), soil water potential and relative humidity all had significant correlation with ginsenoside contents in P. ginseng leaves (P<0.05). HMGR expression in P. ginseng leaves was negatively correlated with Rb₂ content (P<0.05), SS expression was negatively correlated with Rg₁ or Re content (P<0.05), and β-AS expression was negatively correlated with Rc content (P<0.05) and Rb₂ content (P<0.01). Grey correlation analysis results showed that the major ecological factors that influenced ginsenoside contents in P. ginseng leaves were temperature, PAR, soil water potential and relative humidity, with their grey correlation values ranging from 0.727 9 to 0.871 1.【Conclusion】Under the regulation and control of ecological factors, the synthesis and accumulation of ginsenosides were influenced by the expression of involved key enzyme genes.

Abstract:【Objective】To study the influences of four different host plants on the growth, development and reproduction of Leucania loreyi (Duponchel) (Lepidoptera: Noctuidae).【Method】Under laboratory conditions of (24±1) ℃, (75±5)% relative humidity and 12 h light∶12 h dark photo period, the larvae of L. loreyi were fed on maize (Zea mays), rice (Oryza sativa), sugarcane (Saccharum officinarum) and barnyard grass (Echinochloa crusgalli) repectively. The development duration, survival rate, pupal weight and fecundity of L. loreyi were observed, and the life table parameters were calculated.【Result】The larva growth duration was the shortest when feeding on maize (20.18 d), and the longest when feeding on sugarcane (25.24 d). The survival rate from egg to pupa was the highest when feeding on maize (68%) and the lowest when feeding on barnyard grass (58%). The female pupa was the heaviest when feeding on maize (32.43 mg) and the lightest when feeding on barnyard grass (22.61 mg). The fecundity per female was the highest when feeding on maize (1 019.42 eggs) and the lowest when feeding on sugarcane (665.27 eggs). The intrinsic rate of increase (r_m) of L. loreyi was 0.13, 0.12, 0.10 and 0.10 when feeding on maize, rice, sugarcane and barnyard grass respectively, and the net reproduction rate (R₀) was 226.54, 211.48, 153.71 and 171.85 respectively.【Conclusion】Among the four host plants, maize is the optimal host plant for L. loreyi, followed by rice. Sugarcane and barnyard grass may serve as hosts or intermediate hosts.

Abstract:【Objective】To prepare a bacterial agent that is able to degrade beta-cypermethrin (β-CP).【Method】Based on previously isolated and cultured Bacillus subtilis BSF01 which had excellent potential in rapidly degrading β-CP, the bacterial formulation was determined by optimizing additives and dosage. The degrading ability of prepared bacterial agent was evaluated in β-CP-contaminated soil under laboratory conditions.【Result】The optimal formulation was determined to blend 30% bacterial powder with 5% sodium dodecyl benzene sulfonate as wetting agent, 7% acacia gum as dispersant and 4% potassium phosphate as stabilizer, appending kaolin as the carrier to 100%. The quality assessment verified that the spore intensity of prepared bacterial agent reached 6.50×10¹¹ cfu·g^–1 with low water content (≤0.6%), high fineness (≥99%), short wetting time (32 s) and 78% suspensibility. The prepared agent was sprayed on β-CP-contaminated soil by diluting to 100, 1 000 and 2 000 times, respectively. After five days, about 87.50% of residual β-CP in soil was degraded by bacterial agent at 100-fold dilution, which rapidly decreased the residual level of β-CP in soil.【Conclusion】The prepared β-CP bacterial agent exhibits outstanding potential in realistic application with further optimization, which may provide an effective, safe and promising bacterial product for eliminating pyrethroid contamination in agricultural environment.

Abstract:【Objective】To study the genetic geographical difference of Isaria fumosorosea strains isolated from different regions, and the pathogenicity of I. fumosorosea to B-biotype Bemisia tabaci.【Method】Sixteen strains of I. fumosorosea were isolated from soils of Guangdong, Fujian, and Qinghai. The bioinformatics analysis was used to identify ITS sequences similarities of the 16 strains, and the pathogenetic tree was constructed. The immersion method was employed to evaluate the pathogenicities of I. fumosorosea strains against second-instar nymphs of B-biotype B. tabaci.【Result】The ITS sequences similarities between the test I. fumosorosea strains and the reference strains(KX057373.1, KX057375.1) were over 97.7%. Nine strains from Guangdong and six strains from Fujian had no geographic difference. The ITS sequence of Qinghai strain IfTS01 was almost the same as that of reference strain (KX057375.1), and highly similar to the strain IfFJ02、IfFJ06 of Fujian and strain IfGD17 of Guangdong. The fatality rate of B-biotype B. tabaci ranged from 47% to 86% after 10 days treatment with 10 mL^–1 conidia of the 16 I. fumosorosea strains. The most effective strains, IfFJ06, IfGD02 and IfTS01, caused above 80% fatality rate of B. tabaci.【Conclusion】There is no obvious difference of genetic geography among ITS sequences of I. fumosorosea strains isolated from different areas. The pathogenicity of I. fumosorosea strains aganist B. tabaci is not related to its geographical distribution and ITS sequence similarity. There are three strains with high pathogenicity to B. tabaci，which can be used for further research.

Abstract:【Objective】To investigate the diversity of denitrifying bacteria in sediments of Guangzhou Liuxi River, and explore the effects of environmental factors on structure and abundance of bacterial community.【Method】The community structure and abundance of denitrifying bacteria in sediments were analyzed by constructing gene library and real-time quantitative PCR (RT-qPCR). The principal coordinate analysis (PCoA) and redundancy analysis (RDA) were used to investigate the correlations between denitrifying bacterial community and environmental factors.【Result】The composition and abundance of nirS-type denitrifier communities in different sampling sites of Liuxi River had distinctive discrepancy. Phylogenetic analysis showed that most of nirS gene sequences obtained in sediments had distant relationships with the known denitrifying bacteria, and the relationships with microorganisms from other environments were closer. The species that had close relationships with nirS-type denitrifier in sediments of Liuxi River were Rhodanobacter, Paracoccus, Polymorphum gilvum, Herbaspirillum and Thauera. Ammonium (NH₄⁺-N) and nitrate (NO₃^–-N) contents had decisive effects on the structure of denitrifying bacterial community. The nirS gene copy numbers were ranged from 8.26×10¹ to 5.45×10⁴ g^–1, and nirS-type denitrifier abundance was significantly correlated with chemical oxygen demand, total nitrogen, ammonium and nitrate concentrations.【Conclusion】The abundant occurrence of chemical contaminants and reactive nitrogen in Liuxi River significantly influences denitrifying bacterial community structure and diversity.

Abstract:【Objective】Evaluating the soil fertility of different forests by a variety of evaluation methods, analyzing the influences as well as differences and similarities of these evaluation methods on soil fertility comprehensive evaluation and providing a theoretical basis for forest soil nutrient management and sustainable development in South China.【Method】Five kinds of forests, including Acacia spp. plantation, Cunninghamia lanceolate plantation, Eucalyptus urophylla plantation, Pinus massoniana plantation and broad-leaved mixed forest were chosen to measure and analyze bulk density, pH, organic matter, available phosphorus, available potassium, alkaline nitrogen and total nitrogen in soil at a depth of 0-20 cm. Single index evaluation was carried out by membership function and partial correlation analysis. Combined with correlation coefficient method, principal component analysis, grey correlation analysis and Nemerow index method, comprehensive evaluation of soil fertility was conducted for five forest stands.【Result】The soil bulk density of five stands were ranged from 1.24 to 1.29 g·cm^–3, and the values of pH were ranged from 4.11 to 4.24. The contents of organic matter were ranged from 21.43 to 28.18 g·kg^–1, the contents of available phosphorus were ranged from 1.12 to 1.42 mg·kg^–1, the contents of available potassium were ranged from 40.62 to 55.20 mg·kg^–1, the contents of alkaline nitrogen were ranged from 106.12 to 132.28 mg·kg^–1 and the contents of total nitrogen were ranged from 1.03 to 1.45 g·kg^–1. According to the second national soil classification standards, the levels of organic matter and total nitrogen contents were above average values, while the level of available phosphorus content was low, the content of available potassium were ranged from low to below average level, and the content of alkaline nitrogen were ranged from above average to high level. The contents of organic matter, available potassium, available nitrogen and total nitrogen in broad-leaved mixed forest were significantly higher than those in some plantations. Organic matter played the most important role in soil fertility, while available phosphorus was a limiting factor affecting soil fertility. The results of comprehensive evaluation of four kinds of evaluation methods were consistent. The range of soil fertility from high to low was broad-leaved mixed forest > C. lanceolate plantation > P. massoniana plantation > A. spp. plantation > E. urophylla plantation.【Conclusion】The soil fertility accumulation of broad-leaved mixed forest is better than those of other plantations, while the soil of E. urophylla plantation have low fertility. The applications of phosphorus and potassium fertilizer and the adjustment of soil acidity should be emphasized in the management of forest soil nutrients in South China.

Abstract:【Objective】Using Populus alba×P. berolinensis-Hosta plantaginea fallen leaves and turf grass clippings as basic materials, to screen the optimum decompositon condition of mixed materials by adjusting C/N ratio and pH value.【Method】The mixed materials of P. alba×P. berolinensis-H. plantaginea fallen leaves and turf grass clippings were cultured in thermostatic room for 60 days to conduct aerobic decomposition. Different C/N ratios (10, 15, 20) and pH values (4, 7, 10) were setted to explore their effects on contents of water soluble organic carbon (WSOC), humic-extracted acid C(HEC), humic acid C(HAC), fulvic acid C(FAC) and humin C(HuC) during the decomposition process.【Result】HEC and HAC extracted from the mixed materials were both accumulated at the end of culture while C/N ratio was 10 or 15, and C/N ratio of 20 was more beneficial to the microbial mineralization and turnover of WSOC, HEC and HuC. When C/N ratio was 15 or 20, the humic quality of mixed materials was enhanced after 60 days of culture. The transformation of FAC to HAC was partly restrained if C/N ratio was set to 10 by applying more nitrogen into the mixed materials. The C/N ratio of 20 was more beneficial to the simplification of humic acid (HA) molecular structure, followed by C/N ratio of 10. C/N ratio of 15 was more favorable to the stabilization of HA molecular structure. The microbial mineralization of HuC could be promoted when pH value of mixed materials was 7, and the contents of HEC and HAC were increased by 30.0% and 69.0% respectively in the decomposition process. When pH value of mixed materials was adjusted to 10, HAC/FAC ratio was mostly promoted and increased by 78.3%, while pH value of 4 or 7 had relatively smaller effect on HAC/FAC ratio promotion.【Conclusion】The combination of C/N ratio of 15 and pH value of 7 mostly promotes the decomposition of mixed materials composed with P. alba×P. berolinensis-H. plantaginea fallen leaves and turf grass clippings.

Abstract:【Objective】To illuminate the photosynthetic and carbon sequestration characteristics of rare and endangered species of Magnoliaceae, and provide theory and technology bases for their conservation and utilization.【Method】Manglietia aromatica, M. lucida and M. kaifui were studied with LI-6400 portable photosynthetic system measuring photosynthetic characteristics. Their carbon sequestration and oxygen release amounts were estimated to evaluate comprehensively their adaptabilities and ecological effects.【Result】The diurnal variations of net photosynthetic rates of three species displayed bimodal curves with obvious midday depression in July and unimodal curves in October. The daily mean values of net photosynthetic rates of three species in July were 5.35 μmol·m^–2·s^–1 (M. kaifui), 2.87 μmol·m^–2·s^–1 (M. lucida) and 2.78 μmol·m^–2·s^–1 (M. aromatica) successively, and the values in October were 6.46 μmol·m^–2·s^–1 (M. kaifui), 6.24 μmol·m^–2·s^–1 (M. aromatica) and 5.74 μmol·m^–2·s^–1 (M. lucida) respectively. The carbon sequestration and oxygen release amount of three species was in order of M. kaifui>M. aromatica>M. lucida.【Conclusion】The test plants display more vigorous growth in October than July. M. kaifui has the best capacity of utilizing strong light while M. aromatica has the best capacity of utilizing weak light. M. kaifui has the best carbon sequesteration and oxygen release abilities among three species.

Abstract:【Objective】To improve the anti-mold property of heat-treated wood and provide a technical support for expanding the use range of heat-treated wood.【Method】The Pinus massoniana wood was dipped in copper impregnated liquid with pressure according to liquid reduction reaction principle. The heat-treated wood was obtained by heat treatment technics, and anti-mold property of the wood was tested by modified mold culture box test method.【Result】The control group of P. massoniana wood was treated more than 3 hours at 220 ℃ and the mold-resistance effectiveness was lower than 20%. Under the same heat treatment condition, the mold-resistance effectiveness of P. massoniana wood which was impregnated in copper solution was more than 90%. The data of scanning electron microscope (SEM), energy disperse spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) showed that nano-copper was generated in copper-contained P. massoniana heat-treated wood.【Conclusion】The 100 nm copper produced in situ by heat treatment of copper-contained wood can greatly improve anti-mold property of wood.

Abstract:【Objective】To study the distribution of chlorophyll content of Longan (Dimocarpus longan Lour) leaves in different growth periods, realize non-destructive measurement of the influence of pests and diseases on chlorophyll distribution, and provide a reference for evaluating the cold-resistant ability of young leaves, fertilizing amount in the fruiting period and pruning of mature leaves.【Method】Hyperspectral images of Longan leaves in three growth periods were acquired via an online hyperspectral imaging system within the spectral region of 369-988 nm wavelength. An automatic masking method was used to extract the interest regions. The chlorophyll content was measured by the spectrophotometric method. The relationships between the spectral response characteristics and chlorophyll contents of Longan leaves in three growth periods were measured based on Pearson correlation coefficient (r). A partial least squares regression (LSR) model was established. The relationship between the texture feature of selected image and chlorophyll content was analyzed. The spectroscopy and texture features were imported to the spare auto-encoder (SAE) model in deep learning to predict the chlorophyll content of Longan leaves. The distribution of chlorophyll content was predicted using SAE model based on the mapping information.【Result】The peaks of correlation coefficient curves of Longan leaves in three growth periods appeared in the vicinity of 700 nm. The wavelength of the highest correlation coefficient for young, mature and old ripe leaves was 692, 698 and 705 nm, respectively. The correlation coefficient (r) of the most sensitive band in full period was higher than those in three growth periods, which was up to 0.890 3. Among all regression models, the prediction effect of LSR model based on the absorption band of the minimum reflectivity and total reflectivity was the best (R_c²=0.856 8, RMSEc=0.219 5; R_v²=0.771 2, RMSEv=0.286 2), and the determination coefficients of its calibration and validation sets were higher than those based on a single parameter. SAE model importing spectroscopy and texture features performed the best (R_c²=0.979 6, RMSEc=0.171 2; R_v²=0.911 2, RMSEv=0.211 5) and the most stable to predict chlorophyll contents of Longan leaves in different growth periods, its standard deviation was only 29.9% of LSR model.【Conclusion】A method automatically extracting interest region was proposed, its success rate was 100%. The performance of SAE model based on spectroscopy and texture features was more stable than those of regression models based on spectroscopy to predict chlorophyll contents of Longan leaves in different growth periods. SAE model is suitable for predicting the distribution of chlorophyll content of Longan leaves as a non-destructive method.

Abstract:【Objective】The discrete element method (DEM) is commonly used in simulating the motion states of agricultural materials in agricultural production process. The accuracy of discrete element simulation depends on the parameters used in simulation process. In this study, we calibrated DEM parameters to provide a reliable basis for the application of DEM in simulation experiment.【Method】Using maize kernel as object and repose angle as response value, the discrete element calibration method based on response surface methodology was proposed after the comparison of simulation experiment results adopting different parameter combinations with prototype experiment results. Plackett-Burman experiment was performed to test the significance of discrete element parameters and screen the parameters that significantly influenced response value. Then the steepest ascent experiment was used to ascertain the optimum value ranges of significant parameters. Finally, central composite designs were used to design response surface modifying experiments consisting of three factors and five levels.【Result】Corn Poisson's ratio and corn-corn static friction coefficient interacted significantly with each other. The best parameter combination was corn Poisson's ratio 0.438, corn-corn static friction coefficient 0.182 and corn-corn static rolling coefficient 0.051. The simulation experiments were conducted using calibrated parameters above and the mean value of repose angle was 26.89°, approximately to the value in prototype experiment.【Conclusion】The discrete element parameter calibration method for maize kernel based on response surface methodology is feasible, and can improve the accuracy of maize kernel discrete element simulation test.

Abstract:【Objective】To develop a low-cost and simple operational system based on a smartphone for measuring the transmission of LoRa wireless undergroud data.【Method】The measurement system consisted of a smartphone with test App installed and its matching underground test nodes. Scene measurements were carried out with this system. The factors affecting the LoRa wireless data transmission in soil were determined, and the corresponding data transmission methods were discussed.【Result】The test results showed that the system was reliable and easy to operate, and LoRa low-power wide-area network technology could meet the data transmission requirements of wireless underground sensor networks in soil.【Conclusion】The system is expected to provide the appropriate testing method for the engineering application of LoRa wireless underground sensor networks in the future.