Abstract:Agroecology is being strongly recommended and widely extended today in China. In view of the current vague understanding and difficulties in ecological agriculture, this article reviewed briefly the historical track and realistic reason of agroecology practices, and various approaches to sustainable agricultural development at home and abroad. The concept and theory of agroecology practices were summarized and the multiple ways for implementation are introduced. In order to make agroecology become a mainstream practice in agriculture, the problems of agroecology evaluation, potential realization, market renovation, policy support and public participation were discussed. Finally, the opportunity and trend of agroecology development in the future were prospected.

Abstract:Objective Porcine 50K SNP (single nucleotide polymorphisms) chips have been widely used in pig genomic breeding. Meanwhile, genotype imputation can significantly increase the amount of genotype data without increasing the cost of sequencing, which facilitates genetic resolution and genetic evaluation of complex traits. This study was aimed to evaluate the genotype imputation performance from genotype to sequence data of three porcine SNP chips.Method A total of 48 Duroc pigs with three kinds of porcine SNP chips were used as target panel to evaluate the genotype imputation accuracy. A total of 260 pigs with whole genome sequencing data formed a reference panel for genotype imputation. The genotype imputation was performed using Beagle5.1 software to compare the imputation effect of Geneseek 50K, ZhongxinⅠ 50K and Liquid 50K.Result The numbers of original SNPs in three kinds of chips were 50697, 57466 and 50885 respectively. The imputation accuracies (genotype consistencies) were 0.886, 0.886 and 0.898 respectively after imputation without any quality control. After filtering the imputed SNPs with low reliability DR² (Dosage R-squared) <0.95, the imputation accuracies (genotype consistencies) of three kinds of chips were up to 0.974, 0.976 and 0.969 respectively, and the numbers of remaining SNPs were 3393066, 3139095 and 3320627 respectively.Conclusion Genotype data from the three types of porcine SNP chips can be imputed to sequence data with a high imputation accuracy. This study provides useful reference for subsequent breeding application research.

Abstract:Objective To investigate the effects of astragaloside IV (AS-IV) and astragalus polysaccharides (APS) of astragalus extract on the lipopolysaccharides (LPS)-induced inflammation of bovine mammary epithelial cells (BMECs) and the effect on the expression of β-casein in inflammatory cells. Method APS and AS-IV were used to intervene LPS-induced BMECs to detect the changes of cell inflammatory factors, oxidative factors, apoptosis factors and β-casein. Result CCK-8 screening found the concentrations of 1g/L APS and 50, 75, 100 mg/L AS-IV were optimal to stimulate BMECs. After stimulating BMECs with 0.5 mg/L LPS for 24 h, the inflammatory cell model was successfully established. Experiments found that AS-IV and APS could significantly inhibit the expression of lactate dehydrogenase (LDH) in inflammatory cells and alleviate the continuous damage of cell membranes in the inflammatory state; Significantly inhibit the expression of malondialdehyde (MDA) and reactive oxygen species (ROS) in inflammatory cells and alleviate the oxidative damage of cells; Significantly inhibit the expression of IL-6, IL-8, TNF-α inflammatory factors in inflammatory cells, and reduce the inflammatory response of cells; Significantly inhibit the expression of apoptotic proteins in inflammatory cells and inhibit cell apoptosis; Significantly activate β-casein in BMECs inflammatory cells and normal cells, and inhibit the expression of TGF-β and ERK1/2. Conclusion AS-IV and APS can inhibit the inflammatory response of BMECs induced by LPS and activate the expression of β-casein in inflammatory cells at the optimal concentrations.

Abstract:Objective To seek more effective agronomic measures to reduce runoff, sediment and phosphorus loss emissions under the combination of different stacking methods and straw returning densities. Method Under the conditions of natural rainfall, different straw returning densities (0.75, 1.5 kg·m^-2), different straw crushing particle sizes (1, 5 cm), adding water or urea were designed to study the effects on runoff and sediment amount, and phosphorus loss of slope farmland in the middle of Yunnan. Result The straw density of 1.5 kg·m^-2, straw particle size of 5 cm, and water retting could effectively reduce the runoff and sediment yield of tobacco slope farmland by 18.59%–38.60%, 12.50%–38.60%, 10.6%–38.60%. Compared with the treatments of 1.5 kg·m^-2 straw density, 1 cm straw particle size, and water and urea retting, 0.75 kg·m^-2 straw density, 5 cm straw particle size, and water-added could decrease runoff and sediment total phosphorus and runoff PO₄^--P concentration by 2.82%–66.67%, 0.38%–57.53% and 1.97%–64.73% respectively. The ratio of PO₄^--P in runoff was 35.30%–77.59% of the total phosphorus concentration. Straw density of 0.75 kg·m^-2, straw particle size of 5 cm, and water retting could effectively reduce the risk of phosphorus loss in tobacco sloping farmland in Erlongtan small watershed. The total phosphorus loss in runoff and sediment respectively highestly reduced 63.64% and 64.74%, 63.89% and 57.87%, 63.89% and 64.74%. Conclusion The use of 0.75 kg·m⁻² straw density, 5 cm straw particle size and water retting treatment can control phosphorus loss in central Yunnan watershed and reduce the risk of runoff, sediment and phosphorus loss on slope farmland.

Abstract:Objective Aiming at the great loss of nitrogen during swine slurry storage process, effects of open and sealed storage on the physic-chemical properties of swine slurry during the storage process were compared in autumn and winter to provide a theoretical reference for swine slurry storage and return to the field. Method The effects of open and sealed storage on material transformation, nitrogen loss and harmlessness of pig slurry storage were compared in autumn and winter under laboratory condition. The changes of pH value, electrical conductivity (κ), chemical oxygen demand (COD), NH₄⁺-N content, NO₃^-- N content, total nitrogen (TN) content, seed germination rate and heavy metal (As, Zn, Cu, Pb and Cd) contents were analyzed. Result The pH value first increased and then remained relatively stable, κ, COD, the contents of TN, NO₃^--N and heavy metals gradually decreased, NH₄⁺-N content first increased and then decreased gradually, and the seed germination rate gradually increased during the storage of pig slurry. After storage, the proportion of inorganic nitrogen in pig slurry increased significantly (Except for winter open storage). Except Cu and Zn did not meet the requirements of “Water Quality Standard for Farmland Irrigation” (GB 5084—2021), As, Pb and Cd met the requirements of harmlessness and stabilization. However storage also caused serious nitrogen loss, with the nitrogen loss rates of 79.44% and 52.60% respectively in autumn and winter under open storage. Compared with open storage, sealed storage reduced the pH value of pig slurry, significantly reduced the nitrogen loss and Zn content during storage, especially the NH₄⁺-N loss. The nitrogen loss rate of pig slurry after storage in autumn and winter decreased by 36.14 and 21.30 percentage points respectively compared with open storage. However, after storage, the κ of pig slurry was significantly higher than that of open storage, seed germination rate was slightly lower, and there was no significant effect on the contents of other heavy metals (As, Cu, Pb and Cd). Conclusion Although open storage is simple and convenient, but the nitrogen loss is serious, which reduces the fertilizer value of pig slurry after storage. Therefore, farms should be encouraged to store pig slurry in sealed condition.

Abstract:Objective This study aimed to explore plant adaptability and heavy metals accumulation of different landscape plants and the co-planting system in sludge-amended landscape soil and provide a theoretical basis for the sewage sludge landscape utilization and the selection of landscape plants for heavy metals remediation.Method Landscape tree Bischofia javanica and landscape ground cover plant Dianella ensifolia, Syngonium podophyllum, and Schefflera odorata were selected as tested plants. The greenhouse pot experiment contained seven treatments, including four kinds of plant species monoculture, and co-planting of B. javanica with three kinds of landscape ground cover plant, respectively. In addition, substrate without planting was designated as control (CK). The seedlings were harvested after six months. Plant dry biomass, root activity, root antioxidative enzyme activity, root morphology, plant heavy metals accumulation, and the fraction changes of soil heavy metals were analyzed.Result Compared with monoculture treatment, the treatment co-planting with S. podophyllumt significantly reduced the dry biomass, root superoxidase dismutase (SOD) activity and root activity of B. javanica. In contrast, the treatment co-planting with S. odorata significantly increased the total root length, total surface area, root volume, specific root length, root peroxidase (POD) and catalase (CAT) activities of B. javanica. The treatment co-planting with B. javanica significantly increased the dry biomass, root total volume, and root CAT activity of S. podophyllum. Compared with monoculture treatment, the treatment co-planting with D. ensifolia increased the Cd accumulation of B. javanica by 238.73%. The treatment co-planting with S. odorata increased the Cd, Cu, and Ni accumulation of B. javanica by 278.76%, 53.68%, and 71.44%, respectively. The treatment co-planting with B. javanica increased the Cd, Cu, Zn, and Ni accumulation of S. podophyllum by 161.61%, 139.77%, 78.37%, and 65.70%, respectively. Also, the exchangeable and Fe-Mn oxides fractions of Cd were significantly reduced but the residual fractions of Cd, Cu, and Ni were significantly increased by co-planting of B. javanica and S. podophyllum.Conclusion Compared with monoculture treatment, co-planting of B. javanica with S. odorata and co-planting of B. javanica with S. podophyllum increased the accumulation of heavy metals in sludge-amended landscape soils.

Abstract:Objective The changes of water loss status, soluble sugar content and relative enzyme gene expression in related glyco metabolism signal pathway of cassava stem under different storage temperature and time were studied, and the correlation between trehalose content and water loss rate of cassava stem was analyzed.Method The stem of ‘cassava 60444’ was used as the experimental material. The stem was stored under low temperature of (20±2)℃ and normal temperature of (36±2)℃ for 0–30 d after harvest. The water loss status and soluble sugar content were determined, the change of related enzyme gene expression in the signal pathway of sugar metabolism was analyzed by real-time fluorescence quantification PCR, and the correlation between trehalose content and water loss rate of cassava stem was analyzed by Pearson method. Result The water loss rates of cassava stem in low temperature storage group at 10, 20, 30 d were significantly lower than those in normal temperature storage group (P<0.01). The trehalose contents of cassava stems under low and normal temperature storage overall increased to different degrees with the extension of storage time, and the content of low temperature storage group was significantly lower than that of normal temperature storage group at 10, 20, 30 d (P<0.05). The contents of sucrose, glucose, fructose and maltose in low and normal temperature storage groups all showed a decreasing trend with storage time. Correlation analysis showed that there was a strong linear correlation between trehalose content and water loss rate in low and normal temperature storage groups, and there was significant difference in the regression equations between the two storage groups with the smaller correlation coefficient under low temperature storage. Real-time quantitative PCR analysis showed that the expression of glycolysis related genes increased under low and normal temperature for 10–30 d, most related genes in low temperature storage group had lower expression level, and the expression of trehalose-6-phosphate synthase gene (METPS-1) at 10, 20, 30 d was significantly low than that in normal temperature storage group (P<0.05). Conclusion Low temperature storage of cassava stem contributes to retaining water, slowing down glycolysis rate and prolonging storage time. There is a strong correlation between trehalose and water loss stress of cassava stem, and the increase of trehalose content is helpful to improve the water retention capacity of cassava stem.

Abstract:Objective To explore the acute toxic effect of glyphosate on Pomacea canaliculata under the combined pollution of glyphosate and H₂O₂. Method Using the hydrostatic biological test method, adult Pomacea canaliculata with uniform growth in the field were collected, and exposed to water with different concentrations of glyphosate and similar to the average concentration of H₂O₂ (50 μmol·L^-1) in precipitation of Guangzhou. The influences of glyphosate on some water quality indexes of P. canaliculata habitat and acute toxic effects of P. canaliculata under oxidative deposition conditions were studied.Result For the water quality index, oxidation-reduction potential (ORP) increased with the increase of exposure time, from 330 mV to about 540 mV; The change of pH with the increase of exposure time increased or decreased under different treatments, and finally maintained between 7.0 and 8.5; The concentration of dissolved oxygen (DO) was between 8.5 and 16.0 mg·L^-1, and there was no obvious variation trend. The three water quality indexes above were within the range that the growth of P. canaliculata could adapt to. Acute toxicity tests indicated that glyphosate had low toxicity to P. canaliculata, and the 50% lethal concentration (LC₅₀) in 48 h was 133.479 mg·L^-1 with or without H₂O₂ deposition. The anti-oxidative stress enzymes of superoxide dismutase (SOD) and catalase (CAT), as well as energy metabolism-related enzymes of amylase (AMS) and lipase (LPS) in P. canaliculata were firstly up-regulated, then suppressed, and finally adapted to up-regulation. It showed that in the process of poisoning, P. canaliculata could slowly adapt to the stress environment and continuously improve its stress resistance, so that it could survive normally in this stress. Conclusion Under the condition of oxidative deposition, the acute toxic effect of glyphosate on P. canaliculata is low, and the activities of the four related typical enzymes are generally up-regulated. It is ineffective and unrealistic to try to inhibit P. canaliculata through herbicide weeding at the same time.

Abstract:Objective The metabolites of Epicoccum sorghinum L28 from mangrove and their antifungal activities were studied.Method The metabolites were isolated and purified by column chromatography, and their structures were identified by spectral technique. The minimum inhibitory concentration (MIC) of the metabolites against Fusarium graminearum and F. oxysporum were tested by the double dilution method.Result Ten compounds were isolated and identified as 7-hydroxy-2, 5-dimethyltrichroprimorone (compound 1), livistone A (compound 2), barceloneic acid A (compound 3), barceloneic lactone (compound 4), 2'-O-methylbarceloneate (compound 5), spirostaphylotrichin R (compound 6), spirostaphylotrichin U (compound 7), β-sitosterol (compound 8), β-carotenoside (compound 9) and β-adenosine (compound 10). 7-hydroxy-2, 5-dimethyltryptophanone displayed strong inhibitory effect against the growths of F. graminearum and F. oxysporum with MIC of 100 μg/mL. 2'-O-methylbarceloneate showed moderate inhibitory activity against F. oxysporum with MIC of 200 μg/mL.Conclusion Compounds 1 and 5 could be further studied as the lead compounds of corresponding antifungal pesticides.

Abstract:Objective In order to study the colonization rule of Bacillus subtilis biocontrol strain SEM-9 in the rhizosphere of crops and its influence on the microbial diversity of rhizosphere soil. Method The strain SEM-9 was labeled with green fluorescent protein by natural transformation method, and the colonization in rhizosphere soil, on root surface and in root tissue were observed by inverted fluorescence microscope. The changes of microbial diversity in rhizosphere soil treated with the strain SEM-9 were analyzed by high-throughput sequencing using soil with soilborne diseases as test material. Result The recombinant strain SEM-9-pGFP₂₂ stably expressing green fluorescent protein was constructed. The observations of fluorescence microscopy showed that SEM-9-pGFP₂₂ could colonize on the rhizosphere soil and root surface, but not in root tissue or cell. After treated with the SEM-9 suspension, the incidence rate of cucumber soilborne disease significantly reduced, and the fungal diversity in rhizosphere soil increased. Conclusion The GFP labeling method of SEM-9 strain was successfully established, and the rhizosphere colonization rule of the strain and the control effect on cucumber soilborne diseases were clarified, which lays a foundation for the later development of alternative microbial fertilizer.

Abstract:Objective Mulberry bacterial wilt is a seriously harmful bacterial disease caused by Ralstonia solanacearum. Therefore, it is of great significance to establish a rapid and sensitive detection method for R. solanacearum to effectively control mulberry bacterial wilt.Method Pectate lyase gene of R. solanacearum was used as the target. Based on the primer design principle of isothermal multiple self-matching-initiated amplification (IMSA), combining the loop-mediated isothermal amplification (LAMP) reaction system, a rapid and effective IMSA-LAMP method for detection of R. solanacearum was established. The optimal reaction parameters of this method were screened.Result The IMSA-LAMP method based on pectate lyase gene could complete the specific detection of positive samples within 45 min at 64.5 ℃, and the detection sensitivity of R. solanacearum template DNA was 200 fg/μL (the corresponding bacteria detection sensitivity was 1×10² CFU/mL); The detection rate of suspected mulberry bacterial wilt samples collected in production was 87.5%.Conclusion This method has good practicability and can provide new technical support for the rapid detection, diagnosis and epidemic prevention of mulberry bacterial wilt.

Abstract:Objective To clarify the species of stem nematode from diseased sample of Codonopsis pilosula in Gansu Province. Method Species identification of stem nematode was carried out by combing morphological analysis, phylogenetic analyses of ITS-rDNA and 28S-rDNA sequences, PCR with species-specific primers as well as PCR-ITS-RFLP.Result The morphological characteristics of the stem nematode population from C. pilosula in Gansu was similar to those of Ditylenchus arachis. The ranges of measurement values were basically agreed with those of D. arachis although some average values were different. The phylogenetic analyses revealed that the tested population was clustered into the same branch with D. arachis. The fragment amplified with specific primers, and PCR-ITS-RFLP map of this population were consistent with those of D. arachi. Conclusion The stem nematode population from C. pilosula in Gansu was identified as D. arachis based on morphological and molecular characters. D. arachis has occurred and distributed in Gansu.

Abstract:Objective An expert system for diagnosing citrus diseases and pests based on fault tree analysis was developed to solve the problems of insufficient popularization of professional plant protection knowledge and lack of efficient diagnosis methods in the prevention and control of citrus diseases and pests. Method First, fault tree analysis method was used to calculate the occurrence probability of diseases and pests and establish a knowledge base of diseases and pests. Secondly, based on the knowledge base and forward reasoning strategy, the reasoning engine of the expert system was designed and implemented. Finally, Weixin DevTools were used to equip the calculation rules of fault tree analysis method and the inference engine of expert system in weixin mini program, and build the expert system based on fault tree analysis method. Result We established an expert system for diagnosing citrus diseases and pests with five functional modules: Pest knowledge module, latest information module, knowledge base query module, diseases and pest diagnosis module as well as user center module. After testing, the system could run smoothly in different types of mobile phones. The average size of memory occupied was 175 megabytes, the average time for system startup was 1.0984 s and the average time for page switching was 0.0495 s. After running the system continuously for 1 h, the connection between the mobile phone and the server was normal. Conclusion The system is stable and reliable, and the page style is displayed normally. Users can exploit the system to diagnose diseases and pests and obtain corresponding control methods. Meanwhile, users can also learn professional plant protection knowledge from the system.

Abstract:Objective The goal was to in depth study the pruning process characteristics and cutting mechanism of fruit branches, and provide a reference for optimizing the core cutting components of pruning machines and improving the cutting performance of electric pruning machines.Method Taking the branch of ‘Shixia’variety of longan as the test object, ANSYS/LS-DYNA was used to perform finite element simulation of the branch cutting process. We built a branch cutting test platform for cutting experiments, verified the accuracy of the simulation model, used a high-speed camera to observe the branch cutting process, analyzed the stress distribution and cutting mechanism of moving blades, branches, and fixed blades in the cutting process, and determined the area where the maximum equivalent stress occured. Result The cutting process of actual test and simulation test could be divided into five stages including the extrusion stage, cutting-in shearing stage, stable shearing stage, shearing stage and branch vibration stage. The actual cutting force was slightly higher than the simulation value. The maximum relative error between the actual value and the simulation value of the peak cutting force of the cutter for cutting 10，15 and 20 mm diameter branches was 7.8%, and the average relative error was 7.0%. The trends of the experimental and simulated cutting force curves were roughly the same. During the cutting process, the maximum equivalent stresses of the moving blade, branch and fixed knife appeared near the cutting edge, branch and fixed knife cut. The maximum equivalent stresses of the moving blade and fixed knife were both less than the yield limits of the tool materials, and the tools would not fail.Conclusion The finite element model is basically consistent with the actual situation and has certain reference value for the design and improvement of pruning machine.

Abstract:Objective In order to meet the field operation requirements, the UAV needs not only a rotor with the function of flexible take-off and landing, but also fixed wings with the characteristics of long endurance. A new agricultural plant protection UAV with X-shaped rotor and fixed wing hybrid structure as well as tilting function was designed. Method According to the load dynamic requirements of farmland spraying operation, the airfoil and parameters of the lifting device of UAV were designed. The body structure of the plant protection UAV was built using SolidWorks software. The aerodynamic simulation analysis of the increasing lift and speed parameters of the plant protection UAV was carried out using the Fluent software and Spalart-Allmaras turbulence model. Result The simulation results showed that the lift coefficient was positively correlated with the attack angle and the airspeed, and the influence of the attack angle was stronger when it changed from 4° to 6°. The lift coefficient reached 0.81 when the attack angle corresponded to the 5°-30° tilt angle. At the airspeed of 5 m/s, the relationship between the attack angle and the tilt angle almost showed linear distribution. Forward tilt of the nose could increase the lift coefficient, and then increase the payload, so that the overall operational efficiency of plant protection UAV was improved.Conclusion The study provides a basis for the design of plant protection UAV with tilt wing, and also offers a new idea for improving the endurance time and operation efficiency of plant protection UAV.