Abstract:噬菌体在地球表层生态系统中的元素循环及污染物转化的微生物群落调控中发挥重要作用。相比于水生系统，土壤高度的异质性和病毒颗粒的高吸附度给土壤中噬菌体的研究带来挑战，尚未引起足够的关注。本文介绍了土壤噬菌体的形态与生命周期分类、以及噬菌体的提取和分析方法；探讨噬菌体调控土壤微生物群落结构以及碳、氮、磷、硫等生命元素循环与重(类)金属转化的科学联系；揭示其生物地球化学机制，阐明其生态功能和环境意义；并对土壤中噬菌体未来研究重点进行了展望。

Abstract:Objective To reveal the effect of humic acid alkaline fertilizer on banana growth and its promotion mechanism, and provide a theoretical basis for the development, popularization and application of the humic-acid alkaline fertilizer. Method Banana pot experiment was carried out. Banana biomass, soil microorganism, enzyme activity, root activity, soil nitrogen and phosphorus nutrient content were measured to identify the efficacy of humic acid alkaline liquid fertilizer.Result Compared with conventional compound fertilizer and non-humic-acid alkaline liquid fertilizer, humic acid alkaline fertilizer could promote banana growth and biomass, increase root activity. The soil urease and acid phosphatase activities, soil mineral nitrogen and available phosphorus content, number of bacteria, fungi and actinomyces increased obviously. Leaf area and biomass increased by 50–100 cm² and 10%–21%, respectively. The root activity increased by 89%–188%. Soil urease and acid phosphatase activity increased by 25%–91% and 2.4–3.5 times, respectively. The number of soil bacteria, fungi and actinomycetes of humus-acid alkaline liquid fertilizer were 1.6–14.4, 1.7–26.7 and 2.3–3.8 times those of compound fertilizer treatment, respectively. The corresponding data of the humus acid alkaline liquid fertilizer were 3.0–10.6, 3.9–56.0 and 1.2–2.0 times of those of alkaline liquid fertilizer without humus acid, respectively. Conclusion Application of humic acid alkaline liquid compound fertilizer could obviously promote banana growth. The mechanism was that the acidic soil environment was improved by the alkaline fertilizer and then the soil microbial diversity increased on the one hand; The humic acid increased soil urease and acid phosphatase activities, the soil nitrogen and phosphorus nutritional status were improved on the other hand to increase soil fertility. Therefore, the synergistic application of humic acid and alkaline liquid fertilizer is a rational measure to supply nutrients to banana and improve soil fertility.

Abstract:Objective As major members of the splicing complex, arginine/serine-rich proteins (SR) not only participate in the process of alternative splicing of plant precursor mRNA, but also play an important role in abiotic stress. SR45 gene is a member of SR gene subfamily, this study was aimed to analyze the structural characteristics and expression patterns of SR45 subfamily proteins in cassava, and provide a theoretical support for further understanding the functions of SR45 subfamily genes in cassava. Method The evolutionary tree of cassava SR gene family was reconstructed by bioinformatics, and the physical and chemical properties, gene structure and conserved domain of cassava SR45 subfamily protein were analyzed. At the same time, transcriptome data were used to analyze the changes of SR gene expression under low temperature and drought stress, quantitative real-time PCR (RT-qPCR) was used to study the specific expression of SR gene members in different tissues and their responses to low temperature stress. Result The cassava SR gene family consisted of 26 members in seven categories, and the SR45 subfamily consisted of five members. The length of proteins encoded by SR45 subfamily genes were 135–417 aa, with relative molecular mass being 14970–47210, PI being 5.19–12.34. It was predicted that they were mainly located in the nucleus and chloroplast. The RS domain and RRM domain encoded by SR45 had Motif 3, Motif 6, Motif 2 and Motif 1 conserved motifs. Transcriptional data and RT-qPCR analysis showed that all SR45 genes were responsive to low temperature stress in cassava, MeSR45-2 was significantly up-regulated, MeSR45-4 and MeSR45-5 were highly expressed in roots and leaves of cassava. Conclusion SR45 subfamily genes of cassava significantly respond to low temperature stress. MESR45-2 gene is selected as the candidate gene for regulating low temperature stress, root and leaf are the main tissues for SR45 subfamily gene research. This study lays a theoretical foundation for the exploration of cassava SR45 gene, and points out a direction for further research on cassava SR45 gene responsive to stress.

Abstract:Objective To clarify the feeding preference and growth adaptability of Spodoptera frugiperda on sugarcane and Rottboellia cochinchinensis.Method Two sugarcane varieties (‘Guitang 42’ and ‘Taitang 22’) , two fruit cane varieties (‘Guiguozhe 1’ and ‘Yellow skin sugarcane’) , and a common weed of R. cochinchinensis in sugarcane field were selected as the research objects. Through the feeding preference experiment and constructing the life table of the experimental population, the feeding preference and growth adaptability of S. frugiperda on sugarcane and R. cochinchinensis were studied. Result The larvae of different instars of S. frugiperda preferred to feed on fruit sugarcane when choosing between sugarcane and fruit sugarcane, and the feeding selection rate on ‘Guiguozhe 1’ was most significantly higher than those of other tested varieties. The larvae of S. frugiperda had a significant feeding tendency to R. cochinchinensis when choosing between ‘Guiguozhe 1’ and R. cochinchinensi. The larval survival rate of S. frugiperda on R. cochinchinensis was the highest, which was 66%, followed by 12% on ‘Guiguozhe 1’. On other sugarcane varieties, S. frugiperda had died in the period of low instar. The life cycle of S. frugiperda could be completed on R. cochinchinensis, and the intrinsic rate of increase (r_m) and finite rate of increase (λ) were 1.16 and 1.52, respectively. Conclusion Compared with sugarcane, S. frugiperda preferes to feed on R. cochinchinensis and has higher adaptability.

Abstract:Objective ‘Candidatus Liberibacter asiaticus’ (CLas), the main species causing Citrus Huanglongbing (HLB), is also the sole pathogen causing agent of HLB in China. Exploring the temporal and spatial distribution of CLas in citrus fruit branch would help timely and accurate detection of CLas, and is of great significance to the prevention and control of HLB.Method The titers of CLas were measured in HLB-affected fruit branches of four traditional citrus cultivars namely Citrus reticulata Blanco cv. Shatangju, (C. reticulata × C. sinensis) cv. W-Murcott, C. maxima cv. Hongxinmi Yu and C. maxima cv. Shatian Yu using real time PCR method. The temporal and spatial distribution of CLas in citrus fruit branches were studied. Result CLas was unevenly distributed in fruit branches with enrichment in the fruits (Fruit pith, centrol axis or seed coat). For the mandarin of Shatangju and W-Murcott, CLas titers were the highest in the piths at the fruit mature stage. For the pomelos of Hongxinmi Yu and Shatian Yu, CLas titers were the highest in the fruit central axes at ripe stage. CLas transferred from the source organs (leaves) to the sink organs (fruits) along with the flow of nutrients in the processes of fruit swelling and ripening. CLas titers kept increasing in central axes and fruit pith, especially significantly increased in fruit pith. Conclusion CLas is enriched with the fruit developmental stages, and such transfer and distribution pattern of CLas in fruit branches can be explained by the theory of plant source-sink relationship.

Abstract:Objective In order to identify the species of pathogens of Camellia oleifera anthrax in Dehong Prefecture, Wenshan Prefecture and Baoshan City of Yunnan Province, and screen their biocontrol bacterium. Method Surveys of infected diseases were conducted from July to September in 2019 and 2020. Diseased leaf samples were collected. The pathogens were isolated by tissue isolation method, pathogenicity was verified by Koch’s Postulation, and the pathogens were identified by morphology and multilocus sequence analysis. Meanwhile, endophytic bacteria were isolated and screened from the leaves of healthy C. oleifera, and the antibacterial effect was verified by plate confrontation method. Result C. oleifera anthrax occurred seriously in Dehong Prefecture of Yunnan Province, with an average incidence rate of 56.18% and a disease index of 53.11. Five major strains were identified from Yunan Province including Colletotrichum gloeosporioides, C. kahawae, C. karstii, C. fiorniae and C. siamense. Among them, C. gloeosporioides was the dominant pathogen, and strain CA17 (C. siamense) had the strongest pathogenicity on living leaves of C. oleifera. The results of plate confrontation method indicated that Streptomyces fulvissimus and Bacillus mojavensis isolated from healthy C. oleifera in Dehong had good antagonistic effect on CA17, and the inhibition rates were 37% and 42% respectively. Result This study provides a theoretical basis for the diagnosis and green control of Camellia anthrax.

Abstract:Objective Mulberry brown spot disease and mulberry ring leaf spot disease are two common fungal diseases of mulberry trees (Morus alba), which are serious and cause great losses in production. This study was aimed to quickly and accurately diagnose the main pathogens of the two diseases, Neophloeospora maculans and Gonatophragmium triuniae.Method Based on the principle of multiplex PCR, specific primers for multiplex PCR were designed for the ribosome internal transcribed spacer (ITS) sequences of two pathogenic fungi, and the conditions of multiplex PCR reaction were optimized. Tests were performed with 45 samples to verify the feasibility of the established multiplex PCR.Result The established multiplex PCR detection system had good operability and good specificity, and the sensitivities for simultaneously detecting DNA of two pathogens were 0.1 and 1.0 pg/μL, respectively. The detection of mulberry disease samples could clearly distinguish the two types of pathogenic fungi in different regions. Conclusion The established multiplex PCR technology can be used for rapid detection of the pathogens of mulberry brown spot and ring leaf spot diseases, and provides a foundation for the prevention and control of mulberry fungal disease.

Abstract:Objective In response to the problem of high moisture content of seed and straw, high bonding force between seed and rice spike at the first harvest season of ratooning rice, there will lead to large amount of broken seeds when harvested by harvesters with traditional rigid rod-tooth threshing device, a rigid-flexible coupled rod-tooth threshing drum based on the axial flow threshing drum was designed.Method The EDEM discrete element simulation software was used to simulate the threshing process, and the average normal striking force and tangential kneading force of three different rod teeth (rigid, flexible, and rigid-flexible coupling) on seeds were obtained through post-processing. Using entrapment loss, breakage rate and unclean rate as the evaluation indexes, the orthogonal bench validation tests were carried out with different drum speed as single factor, and three factors (drum speed, seed moisture content, and rod teeth type) and three levels.Result The EDEM simulation results showed that the average normal striking force and tangential kneading force of the three types of rod teeth on seeds were the largest for the rigid rod teeth and the smallest for the flexible rod teeth at the drum speeds of 650, 750 and 850 r/min, respectively. The results of single-factor test showed that the broken rate of seeds threshed by the rigid rod tooth threshing device was significantly higher than those of the flexible rod tooth and the rigid-flexible coupling threshing devices. The broken rates of the flexible rod tooth, rigid rod tooth and rigid-flexible coupling rod tooth were very high at 900 r/min, with the broken rates of 1.632%, 1.925% and 2.564%, respectively. The unthawed rate and the entrained loss rate of the flexible rod tooth threshing device were significantly higher than those of the rigid rod tooth and the rigid-flexible coupling threshing devices. The unthreshing rates of the flexible rod tooth, rigid rod tooth and rigid-flexible coupling rod tooth were very low at 900 r/min, with the unthreshing rates of 0.286%, 0.071% and 0.240%, respectively. The entrainment loss rate of the flexible rod tooth, rigid rod tooth and rigid-flexible coupling rod tooth were very low at 850 r/min, with the entrainment loss rates of 1.595%, 0.729% and 1.341%, respectively. The results of orthogonal test showed that the order of factor affecting seed entrainment loss and broken rate was rod tooth type > drum speed > seed moisture content, and the order of factor affecting the uncleaned rate was rod tooth type > seed moisture content > drum speed.Conclusion Under the same conditions, the rigid-flexible coupling threshing device can reduce the rice breaking rate while ensuring the seed removal rate. The results can provide a reference for design and application of threshing device of harvester for ratooning rice.

Abstract:Objective In order to meet the agronomic requirements of low sowing rate and precision sowing of hybrid rice potted-seedling raising, and solve the problems of poor fluidity of rice seeds in the seed filling chamber, low seed filling reliability, high missing sowing index and easy blockage of type holes during the operation of seedling raising seeder with type hole roller, a precision seeder with double seed filling type hole roller for hybrid rice seedling raising was designed. Method Based on PLC control technology, a detection and control system for type hole seed filling performance was built, and the key components were analyzed and designed. The simulation tests of the influences of the seed filling performance of different type hole shapes, the seed filling position angle of the first seed filling chamber, and the productivity on seed filling performance were carried out through EDEM discrete element software, to optimize the working parameters of the type hole roller in the first seed filling area. The experimental prototype was developed for post performance test, and rice variety was ‘Peizataifeng’ hybrid rice. The test was divided into two steps. In the first step, the second seed filling mechanism did not act, a three-factor-three-level orthogonal test was adopted to study the effects of type hole depth, productivity and seed filling position angle of the first seed filling chamber on the test indexes, and verify the accuracy of the simulation research. The second step was through the action of the second seed filling mechanism to study the effects of different vibration frequencies on the test indexes under double seed filling, and prove the sowing performance after designing the second seed filling mechanism. Result The results of the first step showed that the order of factors affecting qualified index and replay sowing index was type hole depth > productivity > seed filling position angle of the first filling chamber; The order of the factors affecting the missing sowing index was productivity > type hole depth > seed filling position angle of the first filling chamber. The results of the second step showed that when the type hole shape was oval groove, the seed filling position angle of the first seed filling chamber was 35°, the vibration frequency of the second seed filling chamber was 27 Hz and the productivity was 400?600 discs/h, the qualified index of sowing was above 90%, and the missing sowing index was below 3%. The test results met the agronomic requirements of low sowing rate and precision sowing of hybrid rice. Conclusion The double seed filling method improves the filling performance of each hole of the seeder and reduces the missing sowing index. The results of this study provide references for developing the light and simple precision seeder for hybrid rice potted-seedling raising.

Abstract:Objective In order to avoid seedling and reduce seedling damage rate during the operation of mechanical weeding, a control system of avoiding seedling based on machine vision and proportion integration differentiation (PID) control technology was designed. Method The improved extra-green algorithm was used to gray rice seedlings. The image projection method was used to extract the characteristics of rice seedlings within the region of interest (ROI) to obtain the corresponding image coordinates. The robust regression algorithm was used to fit rice seedlings to obtain the center line of seedling belt. The ground coordinate position of seedling, and the distance between the center of weeding unit and the center line of seedling belt were obtained by transforming the model of aperture imaging. The hydraulic rectifying system was controlled based on PID control algorithm, and the Simulink in Matlab software was used for the simulation analysis of the system. Result The seedling avoidance was realized, and the steady-state response time of the system model was 0.34 s. The performance comparison tests of the control system with and without the control system of avoiding seedlings showed that the control system of avoiding seedlings could obviously reduce the seedling damage of weeding components, with the average seedling injury rate of 3.75%, and the rate without the control system of avoiding seedlings was 24.88%. Conclusion The row-follow control system for mechanical weeding designed in this study can correct the working path of the weeding components in real time, which effectively reduces the seedling injury rate of mechanical weeding. The results of this study can provide some reference for mechanical weeding row-follow control of rice and other crops.

Abstract:Objective In view of the fuzzy and irregular shape of the path boundary in the corn field, the common field navigation line extraction algorithm will have the problem of excessive deviation in practical application of agricultural robot. In this paper, a navigation line extraction algorithm based on discrete factor fusion of camera and 3D LiDAR is proposed for the field of corn at 3rd−5th leaf stage.Method First, three-dimensional lidar was used to obtain corn plant point cloud data. At the same time, the green feature binary images were obtained from the images taken by the camera using the super-green algorithm and the maximum between-cluster variance method, and then the point cloud data after cluster analysis were projected onto the target bounding box in the image. A multi-sensor data fusion support model was constructed for feature recognition. Finally the acquired feature center point was fitted as the navigation baseline. Result The algorithm could adapt well to complex environments and had strong anti-interference ability. The average processing time of a single frame was only 95.62 ms, and the accuracy rate was as high as 95.33%.Conclusion The algorithm solves the problems of shifting in finding feature centroid and unreliable recognition results in traditional algorithms, and provides a reliable and real-time navigation path for the robot to walk in corn field.

Abstract:Objective An orchard navigation scheme based on multi-sensor fusion was proposed to solve the problems of weak signal and poor positioning effect caused by tree occlusion in the GPS navigation process of orchard robot .Method High-precision 3D point cloud data were collected by 16-line lidar, point cloud was preprocessed by Voxel grid filter algorithm, point cloud density was reduced and discrete points were removed, fruit tree rows were clustered by Euclidian algorithm, and the straight lines of fruit tree rows were fitted by improved random sampling consistency (RANSAC) algorithm. According to the relationship of parallel lines, the navigation line was calculated and integrated with inertial measurement unit (IMU) for high-precision positioning of orchard robot. Based on differential steering and pure tracking model, the goal of autonomous navigation and automatic line wrapping of orchard robot was realized.Result After the data fusion of lidar and IMU, the accurate position and pose of the robot were obtained. Compared with the deviation produced by the least square method and the traditional RANSAC method, the lateral deviation based on density adaptive RANSAC method was less than 0.1 m and the heading angle deviation was less than 1.5° when the robot was operating in the orchard at the speed of 0.8 m/s. The deviations were the minimum in the three methods. However, when the robot speed increased to 1.0 m/s, all the deviations increased obviously.Conclusion The orchard robot navigation technology based on multi-sensor fusion proposed in this paper is suitable for most standardized orchards and has important promotion value.

Abstract:Objective The performance of the apple?soluble?solid?content model was influenced by the detection speed and integration time of the near-infrared (NIR) spectroscopy on-line detection device. The aim of this study was to analyze the influence of detection speed and integration time on the applicability of the model, and improve the accuracy of on-line detection. Method The detection speed and integration time of the on-line detection device of NIR spectroscopy were setted as 0.3 m/s and 100 ms, 0.5 m/s and 70 ms, 0.5 m/s and 100 ms, 0.5 m/s and 120 ms, 0.5 m/s and 150 ms respectively. A total of 180 apple samples were used for the experiment, the NIR spectra of five experimental groups of apples were collected at 350~1 150 nm, and the partial least squares (PLS) method was applied to establish the prediction model of apple soluble solid content (SSC). Result There was a threshold for the integration time. When the integration time was shorter than 70 ms, the prediction performance of the model was poor. The prediction performance of the prediction model with the same detection speed and integration time for modeling set and prediction set was superior to that of the prediction model with different dection speed and integration time. Detection speed and integration time would affect the accuracy of on-line detection. The different transmission routes of light inside the apple at different detection speeds and integration time could lead to differences in the internal information obtained by the fiber optic probe, making the prediction performance worse. The 135 representative sample spectra were selected from four groups of 0.3 m/s and 100 ms, 0.5 m/s and 100 ms, 0.5 m/s and 120 ms, 0.5 m/s and 150 ms using the Kennard-Stone algorithm, the prediction models of the mixed detection speed and integration time were established, with the correlation coefficients (R_P) of the prediction set all above 0.85, the root mean square errors (RMSE_P) all below 0.65. Conclusion The established prediction model of mixed detection speed and integration time can better predict apple sugar content and meet the requirements of apple sugar content on-line detection under different parameters of detection devices.

Abstract:目的 开发一种低成本、高响应的维生素C电化学传感器，用于实现果蔬中维生素C含量的快速检测。方法 通过在铅笔芯电极上修饰金纳米颗粒和多壁碳纳米管，构建具有维生素C强催化响应的MWCNTs/Au/PGE电极。通过扫描电镜、X射线光电子能谱、拉曼光谱和循环伏安法表征电极，采用差分脉冲伏安法确定电极的pH适用范围和最优pH条件。采用时间电流法建立标准曲线和方程，以实现快速检测。最后通过加标回收率法检测番茄中维生素C含量。结果 基于MWCNTs/Au/PGE电极的维生素C电化学传感器可在pH 4~8范围内准确地测定维生素C含量，在pH 5时性能最优。快速检测时检测维生素C的质量分数范围为1~500 μg/g，灵敏度达0.244 μA·(μg/g)^?1·cm^?2。该传感器对葡萄糖、苹果酸和柠檬酸的干扰率均小于1.77%，同一传感器多次测定的相对标准偏差为2.7%。成功检出番茄样品中的维生素C质量分数为69.42 μg/g，加标回收率为109%~113%，相对标准偏差小于2.26%。结论 MWCNTs/Au/PGE电极制备工艺简单，成本低，灵敏度高，测量范围宽，有较强的稳定性和抗干扰性，为实现快速检测果蔬中维生素C提供了新思路。

Abstract:Objective Different plants have different requirements for light intensity and light quality. The goal was to achieve intelligent light supplementation for plants through real-time illumination from LED lights.Method Aiming at the need for sufficient supplementary light for the growth and development of pitaya (Hylocereus undatus) and regulation of fruit stage, an intelligent regulator specially for light supplementation of pitaya was designed using a new generation of the programmable logic controller (PLC) technology and yellow LED lights with wavelengths of 570?590 nm, and the corresponding data transmission protocol was designed. The hardware selection, circuit design and software design were performed, and control strategy and remote communication protocol were establised. Finally, an actual deployment and application experiment was carried out in a 10666 m² pitaya farm in Xinxing County of Guangdong Province. Result The regulator could achieve stable and long-term light supplementation for pitaya through manual, automatic and remote management, and data transmission was stable and reliable. The response time of the regulator was within 3 s, and light supplementation duration was 4 h. After using the regulator to supplement the light，the fruit ripening stage was advanced by 2?4 d, some pitaya trees bore 2?3 more fruits per tree, the output of pitaya fruit increased by 16.7%.Conclusion The device realizes the intelligent supplementary lighting of pitaya. It has obvious economic and social benefits and has a good popularization prospect.