Abstract:Objective The purpose of this study was to generate CD163 gene knockout (CD163-KO) Large White pigs by CRISPR/Cas9 gene editing and somatic cell nuclear transfer technologies, investigate the resistance to blue ear disease and the biosafety effect including physiology, productive and reproductive performances of the gene knockout pigs, and assess the main production performances of CD163-KO Large White pigs.Method In this study, the 11 CD163-KO pigs and five age- and body weight-matched wild type Large White pigs were challenged with NADC30-like strain of porcine reproductive and respiratory syndrome virus (PRRSV). The rectal temperature, PRRSV antibody and virus variation were monitored continuously for 14 days. The lung tissues were examined by immunofluorescence of PRRSV antigen. Expression of CD163 protein on the surface of pulmonary alveolar macrophages in wild type and CD163-KO Large White pigs were examined through immunofluorescence staining. We compared the differentiation potential of monocytes into macrophages between CD163-KO and wild type pigs, and observed their uptake capacities to hemoglobin-haptoglobin complex. In addition, we analyzed the growth and reproductive production of the boars between CD163-KO pigs and wild type control to assess their biosafety and breeding value. Result CD163-KO pigs were completely resistant to NADC30-like strain without impairing the biological function associated with the modified gene, as well as productive and reproductive performances.Conclusion This study is an evidence and supplement of CD163-KO pigs resistance to blue ear disease, and demonstrates that CD163 gene knockout has no potentially negative effects on production performance, which provides evidences for the biosecurity of CD163-KO pigs.

Abstract:Objective Seminal plasma exosomes (spEXs) play a crucial role in sperm maturation, apoptosis and fertilization. This study was aimed to explore the miRNA expression of boar spEXs and the potential regulatory role of miRNA in sperm maturation and functional maintenance.Method The spEXs from Yorkshire boar semen were isolated and the exosomes were identified through transmission electron microscopy, nanoparticle tracking analysis, marker protein expression analysis and high-throughput miRNA sequencing. Result The spEXs were successfully isolated. A total of 329 spEX miRNAs were identified by miRNA sequencing. Through target gene prediction and functional enrichment analysis of highly expressed miRNAs, it was concluded that spEX miRNAs played potential regulatory roles in sperm ejaculation, P53 signaling pathway, prostate cancer, cell response to DNA damage stimuli, negative regulation of apoptosis, acrosome membrane binding, fertilization, etc. Conclusion This study provides basic data for spEX miRNAs regulating sperm motility and sperm fertilization, and provides references for studying the regulation mechanism of semen preservation.

Abstract:Objective The purpose of this research was to understand the biological characteristics and physicochemical resistance of African swine fever virus (ASFV) in China, so as to improve the biosafety level of pig farms for the prevention and control of African swine fever. Method Hemadsorption test and qPCR test were used to verify the inactivation effects of different physicochemical factors (including static treatment, temperature, UVC irradiation, indoor and outdoor drying, sun exposure and disinfectant) on ASFV. Result UVC irradiation for 30 min could inactivate the virus, the longer the irradiation time, the more serious degradation of ASFV nucleic acid. Indoor drying for 2.5 d, outdoor drying for 1.5 d or sun exposure for 30 min could inactivate ASFV, but these three physical factors had no effect on ASFV nucleic acid degradation. ASFV was susceptible to common disinfectants tested in study, except iodate mixed solution, all disinfectants could completely inactivate ASFV when treated at room temperature at the recommended diluted concentration for 15 or 30 min. An increase in temperature (4, 25 and 37 ℃) enhanced the inactivation effect of disinfectants. The presence of organic compound FBS could weaken the effect of disinfectants, and an increase in the volume fraction of FBS (0, 10% and 30%) could reduce the inactivation effect. Conclusion This paper systematically studies the effects of common physicochemical factors on the inactivation of ASFV, which is helpful to fully understand the biological characteristics of ASFV, and has important guiding significance for clinical prevention and control of African swine fever.

Abstract:Objective To explore the regulation roles of microRNA-1285 (miR-1285) and its target DDX3X in Senecavirus A (SVA) infected PK-15 cells.Method By qRT-PCR, double luciferase activity and Western blot, the effects of miR-1285 and its target DDX3X on IFN-β secretion and the RIG-I signaling pathway were studied, and their effects on the expression of SVA 3C protein gene were analyzed.Result In SVA infected PK-15 cells, the expression of miR-1285 increased significantly, and there was a negative targeting relationship between miR-1285 and DDX3X. Both miR-1285 and DDX3X promoted the transcription and protein expression of IFN-β. MiR-1285 regulated MAVS and TRAF3 signaling molecules in the RIG-I signaling pathway by targeting DDX3X. For SVA 3C protein, DDX3X significantly inhibited the transcription of 3C and reversed the up-regulation trend induced by miR-1285.Conclusion After infecting PK-15 cells with SVA, host miR-1285 and its target DDX3X can regulate the expression of IFN-β and the viral 3C protein, which will lay a foundation for clarifying the molecular mechanism of miRNAs regulating SVA infection, and provide a new scientific basis for the prevention, control and diagnosis of SVA.

Abstract:Objective To explore the effect of initiation codon mutation within tva receptor gene (tva c.3G>A) on resistance of chickens to infection by avian leukemia virus subgroup A (ALV-A).Method Sanger sequencing and RT-PCR were used to verify the presence of tva c.3G>A mutation in Chinese yellow-feathered broilers. The effect of tva c.3G>A mutation on infection of chickens by RCASBP(A)-GFP fluorescence reporter virus in vitro was detected using flow cytometry. The effect of tva c.3G>A mutation on infection of chickens by ALV-A was investigated using ALV-A challenge test in vivo. Direct sequencing was used to genotype tva c.3G>A mutation site within Chinese yellow-feathered broiler lines.Result The results of Sanger sequencing and RT-PCR identified the mutation from G to A on the third base in the coding region of tva gene of Chinese yellow-feathered broilers, which caused the mutation from ATG to ATA in the initial codon sequence of tva gene. The result of flow cytometry showed that chicken embryo fibroblasts (CEFs) of wild-type tva c.3G/G were susceptible to infection by RCASBP(A)-GFP, while the homozygous mutant tva c.3A/A CEFs were resistant to infection by RCASBP(A)-GFP, indicating that tva c.3G>A mutation led to chicken resistance to infection by RCASBP(A)-EGFP in vitro. The results of ALV-A challenge test in vivo also indicated that tva c.3G>A mutation led to chicken resistance to infection by ALV-A. Genotyping of tva c.3G>A revealed that homozygous resistance genotype tva c.3A/A was present in lines CB01, CB08, CB10 and CB15, with the frequencies of 0.10, 0.15, 0.23 and 0.08, respectively.Conclusion The tva c.3G>A mutation causes chicken resistance to infection by ALV-A in vitro and in vivo, and the tva c.3G>A mutation site can be used as the genetic resistance site of ALV-A.

Abstract:Objective This study was aimed to determine the effect of compound Chinese medicine ultrafine powders on egg laying performance, reproductive hormone, and related gene expression in laying hens.Method A total of 216 Xinyang black-feather laying hens (307-day-old) were selected and randomly divided into three groups with eight replicates in each group and nine in each replicate. The control group was fed the basal diet, and the experimental groups were fed basal diets supplemented with 0.5% Salvia miltiorrhiza (SM) + 0.25% Ligustrum lucidum (LL) + 0.25% Taraxacum mongolicum (TM)(compound 1), and 0.3% Leonurus japonicus (LJ) + 0.2% SM + 0.25% LL + 0.25% TM (compound 2) ultrafine powders, respectively. The pre-trial period was seven days, and the formal trial period was 120 days. Egg production performance, egg quality, and plasma reproductive hormone level were determined. The expressions of genes related to egg quality were detected by RT-PCR technology.Result Compared with the control group, during days 1-30, 31-60, and 1-120 of the trial, the egg laying rates of the compound 1 group increased by 7.56%, 4.00%, and 5.31% (P<0.05), respectively, and during 1-120 days the egg laying rate of the compound 2 group increased by 5.22% (P<0.05). On day 60 after treatment the plasma estradiol level and relative expression of oviduct PMCA1 mRNA increased by 21.45% and 77.00% (P<0.05), respectively, in the compound 1 group, and the relative expression of oviduct KCNA1 mRNA increased by 70.00% (P<0.05) in the compound 2 group. On day 90, the thickness of the eggshells increased by 12.12% and 9.09% (P<0.05), respectively, in the compound 1 and 2 groups. On day 120, the relative expressions of oviduct CA2 mRNA increased by 86.00% and 66.00% (P<0.05), respectively, in the compound 1 and 2 groups, and the relative expressions of oviduct CDH6, KCNA1 and SLC26A9 mRNA increased by 99.00%, 86.00% and 99.00% (P<0.05), respectively, in the compound 2 group.Conclusion Dietary supplementation with compound Chinese medicine ultrafine powders consisting of LJ, SM, LL, and TM could increase the egg production rate, improve egg quality of laying hen, increase the level of reproductive hormone, and up-regulate mRNA expressions of genes associated with eggshell formation. In addition, compound 1 presents the better effect.

Abstract:Objective The purpose of this study was to analyze the evolutionary relationship between bovine ephemeral fever virus (BEFV) isolate JM 2020 in Guangdong Province and other strains from other regions, and clarify the characteristics of genetic evolution and whole genome, so as to provide information for the epidemic situation and prevention of bovine ephemeral fever disease in China and the world.Method According to the whole genome sequence information of BEFV strain downloaded from GenBank, primers were designed to amplify glycoprotein (G) gene by PCR. The 10 pairs of primers were designed to amplify the whole genome, and the gene sequences of 10 fragments were obtained by sequencing. The whole genome sequences were manually edited and spliced by EditSeq in DNAStar software. Using MEGA 6.0 to construct G gene and whole genome evolutionary tree respectively for evolutionary analysis.Result The G gene and whole genome of the JM 2020 strain had the highest nucleotide sequence similarity with the Thai strain, which were 94.9%-99.3% and 99.0% respectively. The evolutionary analysis showed that JM 2020 was in the same small branch with the 2013 to 2017 Thai strains, while there was a certain evolutionary distance from domestic virus strains such as JB76H and JT02L. Whole genome sequencing results showed that whole genome of JM 2020 was 14 902 nucleotides (nt) in length, including 50 nt leader sequence, 1 296 nt nucleoprotein (N) gene, and 837 nt phosphoprotein (P) gene, 672 nt matrixprotein (M) gene, 1 872 nt G gene, 1 812 nt non-structural glycoprotein II (G_NS) gene, 618 nt α1 and α2 gene, 444 nt β gene, 345 nt γ gene, 6 444 nt large multi-functional enzyme (L) gene and tail sequence of 73 nt, which was separated by 21, 47, 68, 67, 23, 64, 59, 79 and 35 nt intergenic regions. The P' gene (polycistronic product of P gene) of JM 2020 was truncated like qy2017 and the Thai strain. Conclusion The JM 2020 strain is highly similar with the qy2017 strain isolated in 2017 and they are closely related to the evolution of the Thai strain. They have some evolutionary distance with JB76H strain etc. from other regions of China. This study enriches the genome information of BEFV epidemic strains in China and lays a foundation for the prevention and control of bovine ephemeral fever and the research of new vaccines.

Abstract:Objective To obtain the disease-resistant molecular markers in grouper (Epinephelus spp.), and serve for the selective breeding program of disease-resistant grouper strains, so as to solve the problem of frequent occurrence of grouper disease. Method Single nucleotide polymorphisms (SNPs) were screened based on PPAR-δ genomic DNA sequence, and association analysis of resistance to Singapore grouper iridovirus (SGIV) and red-spotted grouper nervous necrosis virus (RGNNV) was performed on these SNPs.Result A total of nine SNPs were detected in the susceptible and resistant groups against SGIV infection, all of which were located in the introns, with the polymorphism information contents (PICs) ranging from 0.177-0.375. Among the SNPs, SNP-S1(g.940T>A) showed low degree polymorphism (PIC<0.25), while the rest SNPs showed moderate degree polymorphism(0.25≤PIC<0.50). The association analysis showed that the genotype frequencies of SNP-S7 (g.4595T>A) were significantly different between SGIV susceptible and resistant groups (P<0.05), the TT and AA homozygous genotypes of SNP-S7 were correlated with SGIV resistance traits, while the AT heterozygous genotypes were correlated with SGIV susceptibility traits. In addition, a total of eight SNPs were detected in the susceptible and resistant groups agasinst RGNNV infection, among which SNP-N1 was located in the exon, with a synonymous mutation, and the rest SNPs were located in the introns, with the PICs ranging from 0.106-0.317. Among the SNPs, SNP-N1 (g.324G>A) and SNP-N2 (g.883A>G) showed low degree polymorphism (PIC<0.25), while the rest SNPs showed moderate degree polymorphism (0.25≤PIC<0.50). The association analysis showed that SNP-N5 (g.2510C>T) genotype frequencies were significantly different between RGNNV susceptible and resistant groups (P<0.05), the CT genotype of SNP-N5 was correlated with RGNNV resistance traits and the CC genotype was correlated with RGNNV susceptibility traits. Conclusion In this study, we successfully screened one SNP marker related to SGIV resistance and one SNP marker related to RGNNV resistance from PPAR-δ genomic DNA sequence. This finding can offer a technical support and a theoretical basis for resistance breeding of grouper.

Abstract:Objective The ecotoxic effects of florfenicol and copper (Cu) residues on soil nitrogen-fixing bacteria were studied to provide a basis for evaluating the environmental risks of veterinary drugs.Method A dominant nitrogen-fixing bacterium RpEC2071 was isolated from peanut root enclosure and treated under florfenicol and Cu stress. We set the blank group (0 μg/mL), florfenicol group (40 μg/mL), Cu group (200 μg/mL) and mixed group (flufenicol 40 μg/mL, Cu 200 μg/mL), and collected samples at multiple time points after dosing. The phenol-sulfuric acid method and 96-well microplate method were used to study the effects of florfenicol and Cu alone or in combination on the production of extracellular polysaccharides and biofilm formation of nitrogen-fixing bacterium. RT-qPCR was used to determine nitrogen-fixing bacterium biofilm formation and the mRNA expression levels of nitrogen fixation-related genes.Result Florfenicol and Cu alone promoted the formation of biofilms, and the biofilm formation capacity of both was about twice that of the blank group. Under mixed stress, the biofilm formation was inhibited, and the biofilm formation capacity of the blank group was 3.1 times that of it. The results of extracellular polysaccharide secretion were basically consistent with the results of the determination of biofilm formation ability. Biofilm-related genes were significantly positively correlated with nitrogen metabolism regulatory genes, and the addition of florfenicol and Cu changed the expression levels of genes such as fliQ, ntrX and nnrR, and it would produce synergistic or antagonistic effects after the combination treatment of florfenicol and Cu.Conclusion The individual or combined stress of florfenicol and Cu affects the expression of biofilm-related genes in nitrogen-fixing bacteria RpEC2071, which in turn affects its ability to form biofilm. This research reveals the ecotoxic potential of veterinary drugs and heavy metal residue stresses on soil nitrogen-fixing bacteria, using florfenicol and Cu as examples. As a result, this can lead to the impairment of the nitrogen-fixing ecosystem in soil.

Abstract:Objective The objectives of this study were to obtain a rational drip fertigation mode for reducing nitrous oxide (N₂O) emission in maize-planting soil, and reveal the effects of soil inorganic nitrogen content on N₂O emission under different drip irrigation amount and nitrogen fertigation ratios. Method In the mobile rainproof shelter, two-season maize experiments with three drip irrigation amount (W₆₀, W₈₀ and W₁₀₀ were 50%-60%, 70%-80% and 90%-100% of field water holding capacity, respectively) and two nitrogen fertigation proportions (F₅₅: 50% nitrogen fertilizer applied to soil as basal fertilizer, and 50% nitrogen fertilizer as fertigation, F₃₇: 30% nitrogen fertilizer applied to soil as basal fertilizer, and 70% nitrogen fertilizer as fertigation; Both of F₅₅ and F₃₇ had the equal nitrogen rate of 180 kg·hm^-2) were carried out. The soil N₂O flux over the whole growth stage and soil inorganic nitrogen content at different growth stages were measured. Soil N₂O emissions at the different growth stages and over the whole growth stage were calculated and the relationships between soil N₂O flux and soil inorganic nitrogen content were analyzed. Result The N₂O emission fluxes of corn soil in two seasons were similar. Under the same nitrogen application ratio, soil N₂O emission fluxes under W₁₀₀ water treatment were higher than those under W₆₀ and W₈₀ in most maize growth periods, indicating that soil N₂O emission fluxes under high water treatment were higher than those under medium and low water treatment. Under the same water treatment, soil N₂O emission flux ratio of F₅₅ was lower than that of F₃₇ except in summer maize seedling stage. During the whole growth period, the cumulative emission of soil N₂O under W₆₀F₅₅ treatment in spring was lower than that under other treatments, followed by W₈₀F₅₅, while those under W₆₀F₃₇ and W₈₀F₅₅ treatments in summer were lower. In addition, in two seasons, soil N₂O flux was significantly correlated with nitrate nitrogen and nitrite nitrogen contents, with correlation coefficients ranging from 0.433 to 0.579 and 0.396 to 0.532, respectively.Conclusion W₈₀F₅₅ treatment (70%-80% field water holding capacity, 50% nitrogen fertilizer as basal fertilizer and 50% nitrogen fertilizer as fertigation) reduces N₂O emission from maize-planting soil. In addition, soil nitrate nitrogen and nitrite nitrogen contents significantly affect soil N₂O emission.

Abstract:目的 挖掘大豆Glycine max MADS转录因子家族成员GmMADS4基因信息，分析其结构及功能。方法 通过生物信息学分析，对GmMADS4基因进行基因结构、编码蛋白信息、保守结构域、系统进化树以及互作蛋白预测等分析。利用烟草叶片瞬时转化法分析亚细胞定位，通过RT-qPCR进行组织部位及响应缺素的表达模式分析，利用下胚轴复合植株转化法分析超量表达GmMADS4对转基因毛根生长的影响。结果 GmMADS4基因开放阅读框长732 bp，编码蛋白相对分子质量为28 000；保守结构域含有MADS-box和K-box，属于II型MADS家族成员，与拟南芥的AtAP3相似性较高；GmMADS4在大豆多个部位均有表达，且在花和种子中的表达量较高；缺氮和缺磷处理均显著增加GmMADS4在叶和根部的表达量；GmMADS4主要定位在细胞核，超量表达GmMADS4显著增加转基因毛根的可溶性磷含量。结论 GmMADS4属于大豆II型MADS家族成员，具有核定位功能，可能在大豆种子和花的发育过程中发挥作用，并参与大豆根部缺磷响应及磷稳态调节。

Abstract:Objective To identify the pathogenic fungi of pepper anthracnose and screen the fungicides with strong inhibitory effects. Method The typical leaves and fruits with anthracnose symptoms were collected from the peppers named ‘Dangwu’ in Huaxi, Guiyang, Guizhou. The pathogen was isolated. Its pathogenicity and classification were determined by monospore isolation, Koch’s postulates, and morphological characteristics combined with multi-locus (ITS, ACT, GAPDH and CHS-1) phylogenetic analysis. The sensitivities of pathogen to six chemical fungicides and six biological fungicides were investigated by the mycelial growth rate method. Result The pathogen causing pepper ‘Dangwu’ anthracnose in Huaxi was identified as Colletotrichum scovillei. The indoor fungicide sensitivity test showed that 12 fungicides all had certain inhibitory effect against C. scovillei. The inhibition effects of 75%(w) trifloxystrobin·tebuconazole WDG, 10%(w) difenoconazole WDG and 250 g/L pyraclostrobin SC were higher with the EC₅₀ of 0.254, 0.731 and 0.745 mg/L, respectively, followed by 200 g/L allylisothiocyanate SL, 3% (w) zhongshengmycin WP, 10 g/L phenazine-1-carboxylic acid SC, 80 g/L ningnanmycin AS, 200 g/L allylisothiocyanate EW and 10 g/L osthol ME with the EC₅₀ of 1.238, 1.307, 1.711, 2.929, 3.175 and 2.191 mg/L, respectively. 10% (w) difenoconazole WDG and 250 g/L pyraclostrobin SC mixed at the volume ratio of 1∶4 or 2∶3 showed an obvious synergistic effect on inhibiting the pathogen based on the joint toxicity test and evaluation results.Conclusion This study can provide references for the field prevention and control of pepper anthracnose using pesticides.

Abstract:Objective In the process of rice production, different control schemes need to be adopted for different pests. The accurate identification and classification of rice pests are the premise of formulating targeted control program. Method A deep residual network of multi-scale feature extraction was proposed based on the Res2Net structure, which could extract pest characteristics more accurately and realize rice pest identification in complex natural background. This network adopted an improved residual structure, replaced the original convolutional kernel with hierarchical class residual connections, increased the sensing field of each network layer, and could extract multi-scale features at a more fine-grained degree. Result The results showed that the model trained by this network could effectively identify rice pests in natural background. The average recognition accuracy of proposed model reached 92.023% on the self-built image dataset containing 22 kinds of the common rice pests, which was superior to the traditional ResNet, VGG and other networks. Conclusion This network can be applied to the automatic monitoring system of rice insect status, which provides a reference for the realization of machine vision monitoring of rice pests.

Abstract:Objective Aiming to address the problem of the current Panax notoginseng disease identification model, with complex structure and large number of parameters, hindering deployment on mobile devices, an improved model based on single shot multibox detector (SSD) target detection is proposed to enable convenient, fast and accurate P. notoginseng disease detection.Method Based on the SSD model architecture, the original feature extraction network (VGG16) was replaced by a lightweight convolutional neural network (MobileNet) to reduce the number of parameters and computation amount of the backbone network. Meanwhile, the RFB module was constructed based on the functional relationship between the size of the population wise receptive field (pRF) in human visual cortex and its eccentricity in the retinogram. The top convolutional layer of the original SSD model framework was replaced by the RFB module to enhance the deep features of the network, improve the detection accuracy and detection speed of the lightweight model, and enable multi-scale P. notoginseng disease detection.Result Compared with the SSD model, the RFB-MobileNet-SSD model reduced the number of network parameters and the computation amount by 96.67% and 96.10% respectively. The model validation using four different disease data under different weather conditions revealed that the improved model improved the accuracy by 4.6 percentage point, recall by 6.1 percentage point, F1 accuracy by 5.4 percentage point, and the time of single image detection was shortened from 0.073 s of the SSD model to 0.020 s, and the size was only 54.6% of the SSD model.Conclusion The improved model not only meets the purpose of real-time detection of P. notoginseng leaf diseases, but is also more convenient for deployment in mobile devices. Moreover, RFB-MobileNet-SSD shows improved performance for small area disease detection and is more resistant to interference in complex environments, making it more suitable for P. notoginseng disease detection in field environment.

Abstract:Objective Aiming at the problems of low accuracy and slow speed of traditional registration methods, we took point cloud of rape (Brassica napus L.) branches as the research object, and proposed a registration method based on ISS-LCG combined feature points.Method The pods of mature rape branches were taken as the research object. The background noise of rape point cloud was removed to obtain the clear and complete point cloud of rape branches. Intrinsic shape signatures (ISS) algorithm was used to extract feature points of point cloud. Linear congruential generator (LCG) algorithm was used to pseudo-randomly select some points of point cloud to constitute key points. Feature points and key points were combined to form ISS-LCG combined feature points. Then, the combined feature points were described by 3D shape context (3DSC) algorithm. Finally, RANSAC + ICP two-step point cloud registration method was used for point cloud registration.Result The precision of on-time registration of rape branch point cloud in pairwise matching was the highest among shooting angles with an interval of 30°. The registration error was about 0.066 mm. Compared with the method without combined feature points, the registration accuracy was improved by 50%-70%. The registration time was less than 48 s, and the average registration time was 8.706 s.Conclusion The proposed method could achieve highly precise and efficient automatic registration of mature rape plants in a controlled environment.

Abstract:Objective In order to expand the applicability of transplanter and realize the automatic feeding of plug seedlings of various specifications of vegetables, this paper designs a universal automatic seedling-feeding device for vegetable transplanting machine.Method The seedling-feeding arm with an adjustable feeding claw was designed, the key parameters were optimized and kinematic analysis was performed. Plug trays with different number of holes could be used by adjusting the number and distance of feeding claws on the seedling-feeding arm and choosing different PLC control programs. The key factors affecting the success rate of seedling feeding were comprehensively considered by analyzing the working process of seedling feeding. Taking the water content of the plug, the height of plug seedling, and the depth of seedling needle into soil as the test parameters, the plug seedlings of lettuce in 72-, 105- and 128-hole plug as the test objects, single factor experiment and multi-factor orthogonal experiment were carried out to explore the effect of different factor on the success rate of seedling feeding.Result The test results showed that when the water content of plug seedling substrate was 40%, seedling height was 50 mm, and the depth of seedling needle into soil was 38 mm, the success rates of seedling feeding for adjustable seedling feeding device were the highest, and the seedling-feeding success rates of lettuce in 72-, 105- and 128-hole plug trays were 95.83%, 96.19% and 96.48%, respectively.Conclusion The design of adjustable seedling-feeding device meets the technical requirements of vegetable transplanting machine for feeding seedlings, and the transplanting effect is good, which can provide a reference for research and development of the universal automatic vegetable transplanting machine.

Abstract:Objective In order to solve the problems of poor training efficiency and low success rate of picking path planning of manipulator using deep reinforcement learning (DRL), this study proposed a path planning method combined with DRL and artificial potential field for citrus picking manipulator in unstructured environments.Method Firstly, the picking path planning problem was solved by the DRL with artificial potential field method. Secondly, the longshort term memory (LSTM) structure was introduced to improve the Actor network and Critic network of two DRL algorithms. Finally, the DRL algorithms were trained in three different unstructured citrus growing environments to perform path planning for picking manipulator.Result The comparison of simulation experiments showed that the success rate of path planning was effectively improved by combining DRL with the artificial potential field method, the method with LSTM structure improved the convergence speed of the deep deterministic policy gradient (DDPG) algorithm by 57.25% and the success rate of path planning by 23.00%. Meanwhile, the method improved the convergence speed of the soft actor critic (SAC) algorithm by 53.73% and the path planning success rate by 9.00%. Compared with the traditional algorithm RRT-connect (Rapidly exploring random trees connect), the SAC algorithm with LSTM structure shortened the planned path length by 16.20% and improved the path planning success rate by 9.67%.Conclusion The proposed path planning method has certain advantages for path planning length and path planning success rate, which can provide references for solving path planning problems of picking robots in unstructured environments.

Abstract:Objective Green roof can reduce and delay the runoff peak of rainstorm through vegetation mitigation and soil media retention. Real time monitoring of rainfall amount, water content of soil media, and runoff are of great significance for scientific research on rainwater retention capacity of roof greening. Method Taking programmable logic controller (PLC) as the core component of hardware control and combining with touch screen, an automatic monitoring system for the rainwater storage effect of roof greening was developed to automatically monitor rainfall events, rainfall amount, air temperature, air humidity and wind speed. Result The measurement results of the real-time monitoring system were consistent with the data of the meteorological department, which indicates that the system can effectively realize the automatic measurement of the overflow amount and the relative humidity of the substrate soil. There were differences in the overflow amount of plant trough and the relative humidity of substrate soil among different vegetations. For example, in a continuous rainfall period during the test, the retention rate of Portulaca grandiflora trough system was 54.75%, the Sphagneticola trilobata system was only 26.63%, and the Sedum lineare system was 38.34%. There were seasonal differences in the water holding capacity of the substrate. The relative humidity of the substrate generally reached more than 70% after the rainfall in August, while the relative humidity of the substrate of Sphagneticola trilobata system was lower than 70% in September, and even lower in October.Conclusion The monitoring system can realize effective, accurate and real-time dynamic monitoring of storage efficiency of outdoor roof greening and ecological environment factors. The rainwater retention capacity, runoff yield characteristics and water retention performance of the matrix soil of the roof plant trough system may be closely related to the meteorological and climatic conditions, rainfall intensity, rainfall amount, plant types, seasonal changes, matrix composition, etc.