Abstract:Mechanized rice direct seeding，which improves the level of rice mechanized planting，is a cost-effective and efficient approach for rice cultivation. Recently, rice direct seeding has rapidly increased owing to rural labour shortages and continuous increase of agricultural production cost. In this article,we analyzed the research and application progress of mechanized rice direct seeding at home and abroad, and introduced in detail the technical system and tools of rice precision hole sowing successfully studied by South China Agricultural University. The future research directions of rice precision hill-drop drilling technology and equipment were proposed.

Abstract:Objective To discuss the feasibility of the structure of hybrid power chassis for high-gap sprayer in the paddy field, solve the problems of deep depression of the paddy field sprayer and poor passing performance in field, and meet rice planting mode and agronomic requirements in the southern region.Method The theoretical analysis of the steering and driving performance of the power chassis was carried out. The key components of the track and wheel traveling device and the transmission system of the whole machine were designed. The finite element software was used to track the trapezoidal bracket under static load conditions. After analyzing, the load distribution and weak parts of the crawler running device under full load were obtained, and the running device was optimized according to the analysis results.Result The chassis clearance was determined to be 950 mm and the track width was 20 mm. Under static full load conditions, the maximum stress on the crawler trapezoidal bracket, which was 128.87 MPa, occured at the hub connection, and the maximum displacement, which was 1.05 mm, occured at the joint of the load bearing wheel, meeting the strength performance requirements. The field test results showed that the driving speed ranged from 1 to 3 km/h, the minimum turning radius of the paddy field was 3 380 mm, the front wheel depth was 115 mm, and the rear depth was 63 mm.Conclusion The wheel-wheel composite power chassis structure is feasible. The performance of the whole machine meets the requirements of paddy field operations. The results of this study have certain reference values for the development of new paddy field high-gap sprayers.

Abstract:Objective To meet the requirement of field flatness in rice planting, reduce the number of times that tractors enter the field, improve the effect and quality of beating and leveling, and realize beating and leveling through one field entry.Method A beating-leveler was developed using the principle of beating followed with leveling. The beating machine, automatic leveling mechanism and automatic elevation adjusting mechanism were developed. Field experiments were performed using the laser-controlled leveling system integrated with automatic leveling function. The roll angles of the tractor and the beating-leveler were respectively measured using two attitude and heading reference systems (AHRS). Field flatness before and after leveling operation was measured using a balance level.Result The roll angle of the beating-leveler maintained within ±1°, while the roll angle of the tractor varied within ±4.5°, indicating that the automatic leveling system obviously improved the leveling stability of the beating-leveler in paddy field. The maximum height difference of the field surface reduced from 17.7 cm (before operation) to 6.7 cm (after operation). Its standard deviation reduced from 4.08 cm (before operation) to 1.75 cm (after operation). The percentage of sampling points with absolute difference of ≤ 3 cm increased from 62% (before operation) to 82% (after operation).Conclusion The laser-controlled beating-leveler can significantly enhance the flatness of the field surface.

Abstract:Objective In order to reduce the reabsorption of rice seeds in pneumatic metering device, a seed cleaning device vertical to the surface of the seed metering plate was designed.Method The force acting on rice seed and the working principle of the seed cleaning device were analyzed when the pneumatic metering device was working, and the force model during the seed suction process was established. The super hybrid rice ‘Wufengyou 615’ was used as the experimental object. The precision test of seed metering device was carried out with or without seed cleaning device. Under a negative pressure of 4.0 kPa in the suction chamber, the effects of two factors, including the thickness of seed cleaning block and the rotational speed of seed metering plate, on seed cleaning were tested and analyzed.Result After using the seed cleaning device, the ratio of 1-3 seeds per hill increased from 62.02% to 90.00%, and the ratio of ≥4 seeds per hill decreased from 37.98% to 5.00%. When the thickness of seed cleaning block was 3.5 mm and the rotational speeds of seed metering plate were 15, 20 and 25 r/min respectively, the ratios of 1, 2 and 3 seeds per hill were 95.18%, 95.16% and 95.23% respectively, and the missing hill rates were 2.07%, 2.76% and 4.56% respectively, which met the requirements of field sowing for super hybrid rice.Conclusion When the negative pressure in suction chamber is constant, reducing the rotational speed of seed plate can improve the cleaning effect of the seed cleaning device and the sowing precision of the seed metering device. Based on the structure of rice pneumatic metering device, we designed a seed cleaning device which can effectively clear rice seeds adsorbed by the seed metering device, and this research provides a basis for improving the precision of rice pneumatic metering device.

Abstract:Objective To better meet the accuracy requirement of vehicle heading angle measure.Method Kalman filter algorithm was proposed. The latitude, longitude and elevation measured by RTK-GNSS receiver were converted to plane coordinates using Gaussian projection. The Gaussian plane coordinates and the accumulated heading angle measured by gyroscope were integrated by Kalman filter, and finally more accurate heading angle was obtained.Result The integrated curve kept the entire variation trend of the heading angle measured by GNSS receiver and the partial variation trend measured by MEMS gyroscope. The curve was smoother than that based on GNSS and gyroscope, and could follow action of vehicle 180° turning.Conclusion The Kalman filter algorithm can measure the vehicle heading angle data in real time and the precision was improved 80% more than the result measured by GNSS.

Abstract:基因编辑技术的发展与应用为植物功能基因研究和作物遗传改良提供了重要的技术支撑。近年诞生的CRISPR/Cas基因编辑系统（主要包括CRISPR/Cas9和CRISPR/Cas12a）与其他的基因编辑技术相比，具有操作简单、效率高等优势，因此在动植物中均得到广泛应用。本文结合CRISPR/Cas基因编辑技术体系的发展历史及最新研究进展，着重介绍了该技术在植物领域中的应用范围和发展方向，以及基因编辑植物的靶点分析方法；对目前CRISPR/Cas基因编辑技术体系存在的问题进行了分析并提出了改进策略。

Abstract:Quorum sensing，which is a cell-cell communication system, is one of the major discoveries in the field of microbiology in recent years. Beginning from the observation of an auto-inducing phenomenon that depends on bacterial population density, it has now been widely accepted that quorum sensing is an important cell-cell communication system existed widely in the microbial community. The track of quorum sensing research has encompassed accidental discovery, range expansion, concept development and transformation of basic research findings to practical applications. Demonstration of the ubiquitous presence of quorum sensing systems in the microbial community has not only provided a new entry point for understanding the regulation mechanisms that govern microbial virulence, and for exploring microbial ecological competition and dynamic balance mechanisms, but also established a solid foundation for regulating microbial ecosystems and developing new disease control strategies. This paper presents a review of some important and representative findings in the area of quorum sensing research, and discusses its future prospects.

Abstract:硫代葡萄糖苷（简称硫苷）是植物中一种重要的植物次生代谢物质，具有很多功能，尤其是其中的萝卜硫苷的降解产物——萝卜硫素具有抗癌作用，因此，受到广泛重视。近年来硫苷研究取得了重要进展。本文系统地介绍了硫苷的功能、种类、分布、运输、生物合成、降解、影响合成和积累的因素、基因工程，并展望其研究前景。

Abstract:果胶是一种结构性多聚糖，也是植物细胞壁的主要成分。果胶裂解酶（PL）则是一类通过β-反式消除作用切割α-1，4-糖苷键，降解去甲酯化果胶产生寡聚糖的酶类。PL的研究将有助于了解植物细胞壁的代谢网络并促进其在食品、造纸、纺织和生物能源等行业中的工业化应用。本文总结了30年来植物果胶裂解酶基因（PL）的鉴定及功能研究的进展情况，归纳了PL在植物生长发育、花器官发育、果实成熟软化、植物与病原微生物的相互作用以及过敏性反应中的生物学功能，并对PL的未来研究进行了展望。

Abstract:Iridovirus is one of the most serious viral pathogens in marine and freshwater cultured fish. Up to now, iridoviruses have been isolated and identified from more than 100 fish species worldwide. Singapore grouper iridovirus (SGIV), a novel species of Ranavirus, was isolated from diseased grouper in Singapore. On the basis of establishing a virus-sensitive cell infection model, morphology, ultrastructure, replication and biochemical characterization of SGIV in grouper host cells were studied by electron microscopy and biochemical analysis. The molecular biological characterizations of SGIV, including viral genome, transcriptome, envelope proteome and viral microRNAs, were systematically analyzed by Omics analysis. The interactions between SGIV and host were investigated from many aspects, including identifying the target tissues of SGIV infection, tracking the single virus entry and transport, non-apoptosis cell death induced by SGIV infection, functions of host immune related genes in virus infection. Meanwhile, a variety of SGIV detection technologies have been developed, including antibody-based flow cytometry, microfluidic chip detection technology platform system, loop-mediated isothermal amplification (LAMP) and nucleic acid aptamer detection method. In addition, SGIV inactivated vaccine, subunit vaccine and DNA vaccine were developed. The results provide a theoretical basis for better understanding of the pathogenic mechanism of SGIV infection, and offer technical supports for the prevention and control of SGIV.

Abstract:Pigs are important agricultural animals and highly similar to humans in terms of genetic background, anatomy, physiological pathology, nutrient metabolism and disease characteristics. Pigs are intensively studied for the improvement of production traits, establishment of animal models for human diseases and xenotransplantation. With the emergence of gene editing technologies, such as ZFN, TALEN and CRISPR, the research on transgenic or gene-edited pigs has achieved a rapid development. This review summarizes the current research advance of transgenic and gene-edited pigs in China. We also review the applications of gene editing technology in agricultural area, such as increasing meat production, improving meat quality, and resisting disease, as well as in biomedical study such as establishing human disease models, animal bioreactors and xenotransplantation for references of pig genetic improvement and medical research.

Abstract:病毒活载体疫苗作为一种新型疫苗，与传统疫苗相比，具有极大的优势与应用前景，是当今与未来疫苗研制与开发的重要方向之一。目前在人类医学和兽医领域，病毒活载体疫苗均取得了大量的研究成果。本文综述了主要的兽用病毒疫苗载体及重组活载体疫苗的最新研究进展，并分析了其发展趋势，为进一步研制新型重组病毒疫苗提供参考。

Abstract:肉、蛋、奶是畜牧业最主要的三大产品，其中，肉的需求量是最高的。肌肉是动物躯体的重要组成部分，仅骨骼肌就已占全身体质量的40%左右。骨骼肌在调节动物新陈代谢、机体运动、能量储存和健康等方面至关重要，是机体功能正常运转的必要组分。骨骼肌发育过程极其复杂，主要包括体节细胞增殖分化、成肌细胞增殖分化、肌管成熟以及肌纤维形成等环节，整个过程受许多遗传因子调控，其中，由微小RNAs（miRNAs）、长链非编码RNAs（lncRNAs）、环状RNAs（circRNAs）等几种类型构成的非编码RNAs（ncRNAs）可以通过靶向关键因子调控骨骼肌发育过程。本文介绍了各类ncRNAs的特征与功能，总结了近年来有关ncRNAs在家禽肌肉生长发育中的研究，阐述ncRNAs在骨骼肌生长发育进程中的表观遗传调控机制，为改善家禽生长发育提供参考。

Abstract:荔枝Litchi chinensis是原产华南且最具中国特色的果树，花果发育与荔枝产量和果实品质密切相关，是荔枝发育生物学最重要的研究内容。本文主要综述了荔枝花芽分化、果实脱落和裂果、果实品质（包括果实和种子大小、果皮色泽、糖酸代谢）形成生理和分子机制等方面的研究进展，并展望了未来的研究方向。

Abstract:Banana is the second largest fruit crop in the world and is the fruit with the largest world trade. Fusarium wilt, caused by the necrotrophic fungal pathogen Fusarium oxysporum f. sp. cubense (Foc), is one of the most destructive banana diseases, which greatly threatens the healthy and sustainable development of banana industry worldwide. In recent years, many efforts have been made on studying disease occurrence, pathogen biology, infection process, epidemiology, whole genome sequencing, banana-Foc interaction and disease management. However, there are few systematic reviews on Foc and Fusarium wilt. Here, we summarize with an emphasis on the disease history and the current status, the races and genetic diversity of Foc, and management strategies of Fusarium wilt, so as to provide references for research and control of this disease.

Abstract:Citrus Huanglongbing (HLB), the highly destructive disease which has been threatening citrus production worldwide, is caused by the yet unculturable bacteria, "Candidatus Liberibacter spp.". HLB can be spread with insect vector and contaminated seedlings. In recent years, with the rapid development of DNA sequencing technology and bioinformatics, genomic analysis had become widely used for HLB research, and had provided the new strategies to overcome the research bottleneck caused by difficulties in bacterial culture. The genomic analysis of "Candidatus Liberibacter spp." not only helps to explore the interaction between "Candidatus Liberibacter spp." and host plant, but also provides an important theoretical basis for resistance cultivation and early detection of HLB. This review summarizes the research progress in citrus HLB and describes the current sequencing strategy and genomic characterization of "Candidatus Liberibacter spp.", with an emphasis on the research progress in genomic analysis of pathogenic mechanism, genetic diversity and molecular detection of "Candidatus Liberibacter spp.".

Abstract:As of 2019, it has been 15 years since red imported fire ant (Solenopsis invicta Buren) was found in mainland China. With the great attention and support from the government and other institutions, our research center has focused on the basic research and application study on the theory and technology of fire ant management. Through systematic researches, the temporal and spatial regulations of fire ant invasion, spread and expansion in mainland China were revealed. The biological basis, regulations and impact of fire ant outbreak on agro-ecosystem were clarified, and its invasive advantages and ecological effects were presented. The theoretical basis for chemical control of fire ant was explained, and monitoring system, quarantine system, and emergency control, eradication and management system were established and widely applied. The results provide scientific and technological supports and guarantee for the control and management of fire ants in China.

Abstract:Palm leaf beetle [Brontispa longissima (Gestro)] is an important Palmae plant parasitical pest. It invaded Hainan in 2002, then broke out, resulted in serious reduction of coconut and betel nut production, and seriously threatened the healthy and sustainable development of the industry of coconut and betel nut in China. At the same time, it posed a huge threat to the green ecological security and tropical natural landscape in the southern coastal areas. After researching for more than 10 years, the key technology system of emergency control and sustainable management were developed and integrated based on clarifying the occurrence and damage rule, and the invasion mechanism of the pest. The technology system has been widely used in the invasive area of the pest, and achieved remarkable benefits.

Abstract:Plants release a variety of volatile organic compounds (VOCs) to mediate intra- and inter-specific interactions with other organisms in the surrounding environment. VOCs are involved in attracting pollinators and seed dispersers, protecting plants from invasion by herbivores, pathogens and parasites and so on. The study of plant volatiles, especially herbivore-induced plant volatiles, has been a research hotspot in the fields of chemical ecology and plant protection for nearly three decades. In this paper, recent advances in the study of plant volatiles-mediated intra- and inter-species relationships are reviewed. We summarized the basic characteristics of plant volatiles and their ecological roles in regulating intra- and inter-species plants, plant-insect, plant-herbivore-natural enemy tritrophic interactions and plant-microbe interactions. We also analyzed the application and prospect of plant volatiles in agricultural production, summarized the unresolved issues in this field and discussed the issues for further research, so as to provide a theoretical basis for the application of plant volatiles in pest control.

Abstract:磷是植物生长发育的必需营养元素，土壤中有效磷含量低是限制作物高产的主要因素。由于长期不当施肥，土壤中累积大量磷素，其中大部分磷是植物难以直接吸收的难溶性无机磷和有机磷。植物在长期进化过程中形成了一系列适应低磷胁迫的机制，其中根系分泌物参与土壤磷活化利用的机制一直是研究的热点问题。本文总结了近十年来关于低磷胁迫调控根系分泌物（有机酸和紫色酸性磷酸酶）合成和分泌的研究进展，对根系分泌物在根际微生态中的重要作用提出了展望，旨在阐明通过控制作物根系分泌物来提高作物磷效率的途径，为培育磷高效作物品种和优化磷肥的田间管理提供思路和奠定理论基础。

Abstract:Over 40% of the arable lands in the world are acidic soils, where low nutrient availability is the major limiting factor for crop production. Root is not only the main organ for nutrient and water acquisition but also the primary interface for communication interactions between plants and soil microorganisms. Exploring the genetic potentials in roots for nutrient acquisition and utilization, as well as improving the composition and activity of microbes in the rhizosphere, have become the important strategies for increasing crop yield while reducing environmental pollution and promoting soil health. Moreover, nitrogen (N) fixed by legumes in symbiosis with rhizobia provides an irreplaceable clean N source in agro-ecosystems, and the symbiosis is also an important factor influencing rhizo-microbiome. Here, we took soybean as an example to summarize the progress of genetic improvement for nutrient efficiency in the roots of leguminous crops in adaptation to acidic soils, and the interactions between roots and rhizo-microorganisms to improve crop nutrient efficiency and soil health. Furthermore, we overviewed the ecological benefits through intercropping nutrient-efficient soybean varieties with maize and tea plants, and thereby provided the theoretical basis and successful examples for genetic improvement of nutrient efficiency in legumes, and its application in sustainable agriculture systems.

Abstract:It has been 32 years since China’s first process of taking seeds of rice and other crops to space with return satellite in 1987. In this paper, the main achievements of crop space breeding over the past 30 years were reviewed, including the mechanisms of rice space mutation, the general key technologies for space bio-breeding, the germplasm (gene) innovation from space mutation, the development and application of new green rice varieties with superior quality and high yield. The perspective development strategies of space breeding were also discussed.

Abstract:Grain shape controls rice yield. Meanwhile, grain shape is related to rice appearance quality, and an important element determing rice quality. With the developments of modern genetics and genomics related theories and technologies, the genetic researches on grain shape are gradually deepened. Now dozens of QTLs controlling grain shape are cloned. This review summarizes the main progresses of genetic researches on grain shape, points out the major problems and analyzes the prospects.

Abstract:In recent one hundred years, rice (Oryza sativa L.) varieties have undergone constant upgrading with the development of modern rice farming. According to the genetic basis, characteristics and evolution of rice varieties, this paper divides rice varieties into five generations (G). The first generation (1G) is tall rice, the second generation (2G) is semi-dwarf rice, the third generation (3G) is intra-subspecific hybrid rice, the fourth generation (4G) is inter-subspecific introgression rice, and the fifth generation (5G) is inter-subspecific hybrid rice. In five generations of rice, 1G of tall rice was replaced by semi-dwarf rice after the 1960s, and no more popularly planted afterwards. 2G of semi-dwarf rice, 3G of intra-subspecific hybrid rice, and 4G of inter-subspecific introgression rice are still being used today. 5G of inter-subspecific hybrid rice is coming to be applied. The emergence of each generation of rice is a major innovation in varieties, and has brought about changes in rice breeding and production. Understanding the evolution of rice generations is helpful to grasp rice development direction.

Abstract:Plant protection unmanned aerial vehicle (UAV) was an important component in China agricultural aviation industry, its rapid development and application in recent years attracted extensive attention. In order to thoroughly and deeply understand the current development situation and problems of plant protection UAV in China, the Department of Agricultural Mechanization Management of the Ministry of Agriculture and Rural Affairs commissioned National Center for International Collaboration Research on Precision Agricultural Aviation Pesticides Spraying Technology of South China Agricultural University to perform a survey and generate a report of "Analysis of the Development Situation and Policy Suggestion for Agricultural Plant Protection UAV in China in 2016". Based on this report, this paper performs statistical analyses on the type distribution, enterprises distribution and ownership distribution of plant protection UAV in China. The overall situation of plant protection UAV in China is presented. The main problems and suggestions related to the research of key pesticide spraying technology, the establishment of relevant standard and the management of supervision in the development of plant protection UAV industry are summarized and put forward. And the development trend of market prospect, key technologies and operation service mode of plant protection UAV are forecasted. It is expected to provide references for scientific research and application of domestic scientific research institutions and enterprises, which can promote and encourage the development process of plant protection UAV industry in China.

Abstract:《Journal of South China Agricultural University》(《JSCAU》for short) is an academic journal sponsored by South China Agricultural University. 《JSCAU》was founded in May 1959, and was one of more than 70 natural science journals founded or re-established in the 1950s. 《JSCAU》 reaches the 60th anniversary of its start publication in 2019. In 60 years, 《JSCAU》 has been growing up with the development of South China Agricultural University, and become a core academic journal of comprehensive agricultural science with certain influence in China through the efforts of generations of committees and editors. By consulting all the journals since its first publication and the related archives and documents, the writer analyses its history, experience and achievement, and prospects the future development of this journal, which will build up confidence of promoting 《JSCAU》 to a new level in the new era and entering the similar top academic journals in China.