《1 Engineering research fronts》

1 Engineering research fronts

《1.1 Development trends in the top 10 engineering research fronts》

1.1 Development trends in the top 10 engineering research fronts

The top 10 engineering research fronts assessed by the field of agricultural engineering research are classified into the following three categories.

In-depth established research fronts: “impact of climate change on crop production” of agricultural resource science, “soil microbial diversity and biological nitrogen fixation” of applied ecology, “plant diversity and global biosecurity” of applied ecology, “plant diversity and global biosecurity” of agricultural resource science, “heavy-metal pollution in soil and stress on crops” of agricultural resource science, “crop nutrition supply and agricultural sustainable development” of crop science, and “impact of forest structure on forest carbon cycle” of forestry engineering.

Newly emerging research fronts: “crop breeding by molecular design” of crop science, “intelligent agricultural equipment” of agricultural engineering, and “mechanism of plant response to biotic and abiotic stress” of agricultural resource science.

Ground breaking research front: “CRISPR/Cas9 genome editing in agricultural biotechnology” of agricultural bioengineering.

Important research fronts are established by a number of core papers, with an average of 123 papers per front. The highest number of papers (491) was written in the area of the “intelligent agricultural equipment” and the lowest number of papers (18) was in the area of “response mechanisms of plants to biotic and abiotic stress.” the majority of the surveyed papers were published in August 2014 (Table 1.1.1) with the average number of citations per papers 82 times greater. During 2012–2017, there were no obvious changes in the number of papers published for eight of the 10 research fronts. However, the number of published papers in the area of the “CRISPR/Cas9 genome editing in agricultural biotechnology” and the “intelligent agricultural equipment” showed a clear increasing trend (Table 1.1.2).

《Table 1.1.1》

Table 1.1.1 Top 10 engineering research fronts in agriculture

《Table 1.1.2》

Table 1.1.2 Annual number of core papers published for each of the top 10 engineering research fronts in agriculture

The top 10 engineering research fronts are summarized below based on the number of publications.

(1)  Crop breeding by molecular design

Molecular-design breeding of major crops belongs to the field of crop science, and is a newly emerging research front. Generally, molecular-design breeding can be divided into directed, systematic and designed molecular breeding. More precisely, molecular breeding integrates the physiological, biochemical, biostatistical and genetic information of the crop-breeding process using bioinformatics as the platform, and the genomic and proteomics databases are used as its foundation. First, the optimal breeding program for a specific crop is designed based on the breeding target and the growth environment. Next, molecular breeding experiments are conducted. Molecular breeding is a technique that integrates multiple scientific and technological areas to simulate and optimize various factors during the breeding process. It identifies the optimal genotypes that are required to meet the breeding objectives, and provides parent- and progeny- selection strategies for achieving the desired genotypes. Molecular breeding significantly improves the predictability and effectiveness of crop breeding, thus transforming the conventional “experimental breeding” into a highly effective “precision breeding.”

(2)  CRISPR/Cas9 genome editing in agricultural biotechnology

The clustered regularly interspaced short palindromic repeats/ CRISPR-associated protein (CRISPR/Cas9) genome editing belongs to the field of agricultural bioengineering. This disruptive technology is a ground breaking research front. Genome editing technology involves the use of endonucleases to cleave deoxyribonucleic acid (DNA) at specific sites, producing double-strand DNA breaks, thus inducing DNA-damage repair. The result is a targeted gene modification. CRISPR/Cas9 is an accurate, highly efficient, and versatile genome-editing tool. CRISPR is a repetitive sequence of regular, clustered, short palindromes that are present in bacteria and archaea. This naturally occurring, ancient defense mechanism relies on a ribonucleic acid (RNA)-guided Cas9 protein to recognize and cut the target sequence, creating a double-strand DNA break. This is a highly specialized immune response mechanism that allows an organism to resist the invasion of foreign genetic material, such as plasmids and viruses. CRISPR/Cas9 technology speeds up the breeding process, solving the problem of the long generation-time encountered in standard breeding.

(3)  Intelligent agricultural equipment

This is a newly emerging research front in the field of agricultural engineering. The development of intelligent control technology for agricultural equipment focuses on the development and expansion of information technology for use in sensors, communication systems, computer vision and image-processing. Examples for sensors include those used for vehicle steering, lowering and raising of surface implements, hydraulic systems for position and pressure- depth. Examples for image monitoring systems include those used for maturity determination based on crop characteristics, seedling thinning and weeding devices that utilize integrated image processing with a visual-sensing function (automatic visual inspection systems), and computer vision and image- processing technology (stereoscopic vision systems) used during the coordinated multi-machine operation of combine harvester-grain cart systems (consisting of the radio load- control of harvester-granary and grain-conveyor speed controllers) to improve the threshing mechanism and the grain-collection performance of combine harvesters.

(4)  Impact of global climate change on crop production

This is an in-depth established research front in the field of agricultural resources science. Global climate change or global warming refers primarily to the rise in the average temperature of the global climate system owing to the excessive emission of greenhouse gases, such as carbon dioxide, due to human activity. Global climate change is expected to ① change the growth environment, seriously affect crop production and sustainable agricultural development, ② impact crop cultivation areas and change cropping systems, and ③ affect the cost and management methods of agricultural production. To cope with the impact of climate change, new strategies, theories, methods and technologies are required to establish new scientific, technological and production systems for crop cultivation.

(5)  Soil microbial diversity and biological nitrogen fixation

This is an in-depth established research front in the field of applied ecology. The nitrogen cycle is closely related to agricultural production and the ecological environment. The application of nitrogen fertilizers increases crop yield. At the same time, fertilizer runoff disrupts the natural balance of nitrogen leading to global environmental problems. Numerous studies have shown that the natural nitrogen cycle is facilitated by microorganisms. Some bacteria can convert atmospheric nitrogen into ammonia by employing a process referred to as nitrogen fixation. Abundant in nature, nitrogen- fixing bacteria can be categorized as free-living, symbiotic and associative. Nitrification is a biological process in which ammonium nitrogen is used directly as a substrate, and it is a key step in the nitrogen cycle. Nitrification is caused by bacteria and archaea, and it is generally performed symbiotically by ammonia and nitrite oxidizers. Theoretical studies of biological nitrogen fixation have focused on the optimal conditions responsible for inducing the nodulation of non-legume crops and improving the efficiency of symbiotic nitrogen fixation. Some of the research areas include effective methods for inducing the formation of symbiotic nodules in key crops using rhizobium invasion, improving the efficiency of the symbiotic nodules of non-legume crops, and the path, the induction site, and the symbiotic mechanism of Rhizobium induced into non-legume host cells. The basic and applied research has focused primarily on developing new nitrogen-fixing plants, for example, by using biotechnology to transform nitrogen-fixing bacteria and existing crops to facilitate the formation of the symbiotic relationship between the new bacteria and the new crops, thus improving their nitrogen-fixing efficiency.

(6)  Plant diversity and global biosecurity

This is an in-depth established research front in the field of applied ecology. Plant diversity includes species, genetic and ecological diversity. The analysis of the mechanisms behind biodiversity generation and the use of various scales to explain the factors that contribute to plant diversity patterns enable us to have a better understanding of the neutral and niche processes that are responsible for the coexistence of species, and helps to recognize potential threats to global biodiversity.

(7)  Heavy-metal pollution in soil and stress on crops

This is an in-depth established research front in the field of agricultural resources science. Heavy-metal pollution refers to environmental pollution caused by heavy metals or their compounds, and is primarily due to human factors such as mining, exhaust emissions, sewage irrigation and products with excessive heavy-metal content. Heavy metals are defined as metallic elements with a density exceeding 4.5 g/cm3. The most common heavy metals include lead, cadmium, mercury, chromium, and the metalloid arsenic. Heavy-metal pollution directly affects agricultural production and food safety, thus endangering the human habitat, and it is one of the most serious ecological and environmental problems currently being faced globally. There are few visible signs of heavy- metal pollution in farming. However, heavy metals are highly toxic, and their chemical behavior and ecological effects are complex. They remain in soil for a long time, and are absorbed by crops and are transferred into the food chain, or migrate into water bodies and the atmosphere. Thus, heavy- metal pollution poses a significant threat to human survival and sustainable development. Given its damaging effect on the environment, food safety and agricultural development, heavy-metal pollution of farmlands has become an important research front in the areas of environmental science and other related fields. The effects of heavy metals on crops are mainly reflected in the crop growth and development process, the physiological and biochemical indices, as well as crop yield and quality. At present, there are two types of remediation techniques for heavy-metal contaminated soil. One is to directly remove the heavy-metal contaminated soil, while the other involves changing the form of the heavy metals in soil to reduce their activity, mobility, and bioavailability. Remediation methods can be categorized as physical, chemical, electrical and biological methods.

(8)    Crop nutrition supply and agricultural sustainable development

This is an in-depth established research front in the field of crop science. In agriculture, soil is the basic means of production, and is the foundation of crop growth. The support of fertilizers is required to improve soil fertility. Therefore, ensuring a stable supply of soil fertilizers and improving the efficiency of their use is the key to realizing sustainable agricultural development. In addition, improving the distribution of soil fertilizers, preventing environmental pollution and arable land degradation, and meeting the nutritional requirements of crops through rational fertilization are essential for achieving green agricultural development. The composition of soil should be thoroughly tested before applying a specific fertilization treatment. For highly fertile soils, ensuring high productivity and the efficient recycling of nutrients are important areas of research.

(9)  Mechanism of plant response to biotic and abiotic stress

This is a newly emerging research front in the field of agricultural resources science. The important research front diagram reveals two major areas of research: biotic and abiotic stress. Of these types, biotic stressors include insects (herbivory) and gray mold (fungus). The main research directions include defense-response, immune response, systemic acquired resistance, induced resistance and signal transduction. In the area of abiotic stress, the most commonly researched factors and fronts include drought, reactive oxygen species, high temperature, salt, oxidative stress and osmotic stress. The research involves content such as the role of abscisic, salicylic, and jasmonic acids in hormone signaling. It also includes major areas such as photosynthesis, stomatal conductance, and antioxidant enzyme systems. With respect to the methods employed, gene expression, transcription factors and transcriptional regulation remain the focus of this research. At the same time, modern “omics” fields, including transcriptomics and proteomics, are also important areas of research.

(10)  Impact of forest structure on forest carbon cycle

This is an in-depth established research front in the field of forestry engineering. The carbon cycle has significant impacts at a global scale, especially climate warming. As forest ecosystems are a principal component of the terrestrial biosphere, changes in the carbon cycle of forest ecosystems have become an important research area in the field of global change. Research into the carbon cycle of forest ecosystem involves experimental methods such as biomass inventory, micrometeorology, the carbon-isotope technique, and geo-information science methods and modeling. Carbon sequestration and carbon-density distribution show large regional and spatiotemporal differences in forest vegetation and soil. In addition, the effect of environmental factors changes in different seasons. Therefore, research into carbon- cycle dynamics in forest ecosystems generally adopts a regional-scale transect carbon source/sink structure as the basis for the development of mainstream methodologies, including spatiotemporal quantification, acquisition of geo- information and modeling. Its goal is to quantitatively analyze the effect of human activity on the carbon budget of forest ecosystems, and to investigate the changes in the carbon cycle in these systems under global climate change. These unique carbon-cycle models for forest ecosystems have helped to broaden the application of modern science and technology, in areas such as computer technology and remote sensing, in the field of forest ecology.

《1.2 Interpretations for three key engineering research fronts》

1.2 Interpretations for three key engineering research fronts

1.2.1 Crop breeding by molecular design

The concept of molecular breeding was first proposed in 2003 by the Dutch scientists Peleman and van der Voort. The rapid development of the whole-genome sequencing technology and the significant progress in research on plant functional genomics have made it possible to conduct molecular design and breeding of crop cultivars at the whole-genome level, thus setting the direction of future development of crop-breeding technology. At the core of molecular breeding is the understanding of key genes, which control important agronomic traits, and their regulatory networks. Biotechnology and other methods are used to acquire or develop elite germplasm resources for use as components of molecular design. The appropriate design components are selected based on the breeding objectives, and are assembled using system-biology methods to cultivate new crop varieties. Compared with standard breeding, molecular-design breeding allows for the precise regulation of agronomic traits at the genetic level, and solves the problem of linkage drag. In addition, it shortens the breeding cycle, thus greatly increasing the breeding efficiency. Compared with molecular marker-assisted breeding, molecular-design breeding is more precise and offers more control. At present, a new generation of genomic-selection breeding technologies, such as zinc- finger nucleases, transcription activator-like effector nucleases (TALENs), CRISPR/Cas9, and oligonucleotide-directed mutagenesis, are being refined. These technologies are expected to be the core of future molecular-design breeding. Molecular-design breeding consists of the following three main steps. (1) Researching the target-trait genes and the relationship between genes, including the genetic population structure, polymorphic marker screening, genetic linkage map construction, and phenotypic and genetic analysis of quantitative traits. (2) Designing the target genotype based on the breeding objectives, under various ecological environment conditions. This step involves using the genetic information of important breeding traits (such as chromosome location and genetic effects of genes, gene-to-trait expression pathways and biochemical networks, gene-gene interaction, the interaction between the genes, and the genetic background and the environment) that have already been identified to simulate the phenotypes of various possible genotypes, so that the genotypes that satisfy specific breeding objectives can be selected. (3) Formulation of specific breeding programs. At present, many obstacles need to be overcome to achieve the full benefits of molecular-design breeding. For example, there is a need for a more accurate analysis of the highly intricate genetic pathways. In addition, a high throughput and accurate identification of crop phenotypic traits are required.

An analysis of relevant academic papers is presented below. According to the table of distribution by country (Table 1.2.1), the USA contributed the majority of core papers, accounting for about 39% of a total of 27 papers, with the citation rate exceeding 50%. In addition, Australia, Germany and France also had a relatively high number of core papers. In terms of research institutions (Table 1.2.2), Cornell University (USA) and ICRISAT were the main contributors. It is evident from the collaboration diagram (Figure 1.2.1) that there was close collaboration between the USA and France. Also, ICRISAT in India and CIMMYT in Mexico also cooperated frequently (Figure 1.2.2). With only five papers published, the Chinese Academy of Sciences had a relatively small number of core papers and frequently cited papers (Figure 1.2.2). The USA, China and Australia had the highest number of cited core papers (Table 1.2.3). In addition, the Agricultural Research Service, US Department of Agriculture had the highest output, accounting for about 22% of the total (Table 1.2.4).

《Table 1.2.1》

Table 1.2.1 Countries or regions with the greatest output of core papers on the “crop breeding by molecular design”

An in-depth analysis of supporting data revealed that the highly cited representative paper entitled “A high-density SNP genotyping array for rice biology and molecular breeding” published in 2014 in Molecular Plant was cited 68

《Table 1.2.2》

Table 1.2.2 Institutions with the greatest output of core papers on the “crop breeding by molecular design”

《Table 1.2.3》

Table 1.2.3 Countries or regions with the greatest output of citing papers on the “crop breeding by molecular design”

《Table 1.2.4》

Table 1.2.4 Institutions with the greatest output of citing papers on the “crop breeding by molecular design”

《Figure 1.2.1》

Figure 1.2.1 Collaboration network among major countries or regions in the engineering research front of “crop breeding by molecular design”

times. One of the most important papers was “crop breeding chips and genotyping platforms: progress, challenges, and perspectives” published in 2017 in Molecular Plant. The most important research institutions included the Chinese Academy of Agricultural Sciences, ICRISAT and Cornell University. A high-frequency keyword analysis revealed that genomic selection, SNP and QTL were the main focuses of scientific research.

1.2.2 CRISPR/Cas9 genome editing in agricultural biotechnology

The emergence of genome-editing technology has led to a new global-scale trend in research. In 2012, it was listed as one of the top 10 scientific breakthroughs in the Science, and in 2014, it was selected by Nature Methods as one of the top

《Figure 1.2.2》

Figure 1.2.2 Collaboration network among major institutions in the engineering research front of “crop breeding by molecular design”

10 most influential methods in biological research over the previous decade. Genome-editing technology involves the use of endonucleases to cleave DNA at specific sites, producing double-strand DNA breaks and thereby inducing DNA-damage repair. The result is a targeted gene modification. The use of this technology speeds up the breeding process, solving the problem of long generation-time encountered in standard crossbreeding. At the same time, because the artificial mutation efficiency increase changed the natural evolution of crops, the environmental and food-safety risks of the genome- edited plans also increased. Four generations of gene-editing tools have already been developed and improved: the ZFNs, TALENs, MGN (meganucleases) and CRISPR/Cas9 systems.

CRISPR/Cas9 is an accurate, highly efficient and versatile genome-editing tool. The basic principle of this editing tool is that the single-guide RNA (sgRNA) recognizes the three conserved nucleotides NGG (N being any nucleotide), called the protospacer adjacent motif (PAM) sequence, in the foreign genome. The sgRNA then guides the Cas9 protein to cleave the DNA strands upstream of the PAM. The double-stranded break in the DNA is repaired through non-homologous end joining, sometimes leading to insertions and deletions of base pairs. As a result, a frameshift mutation of the gene occurs, thus achieving a knockout of that gene. The CRISPR sgRNA requires a sequence of only 20 nucleotides to recognize the target PAM sequence, allowing the Cas9 monomeric protein to function. Compared with other types of gene-editing tools, the CRISPR/Cas9 system is easier to use. In addition, it has a higher knockout efficiency, allowing for more precise gene- editing and significantly reducing the off-target activity. The CRISPR/Cas9 has been widely used to edit important genes of animals and plants.

An analysis of relevant academic papers revealed the following. In terms of distribution by country (Table 1.2.5), the USA, China and Germany contributed the majority of core papers. The USA, China and Germany also had the highest number of citations. In terms of research institutions (Table 1.2.6), the Chinese Academy of Sciences ranked first with 11 core papers, but it had the third largest number of total citations, and was fifth in the average number of citations per paper. It is evident from the country collaboration diagram (Figure 1.2.3) that the USA cooperated most closely with China and Germany, having a leading role in research. The collaboration diagram of main research institutions (Figure 1.2.4) shows that the Chinese Academy of Sciences cooperated closely with the University of the Chinese Academy of Sciences, and had a degree of collaboration with the University of Minnesota (USA). The USA and China had the highest number of cited core papers. In addition, the proportions of cited core papers of these two countries far exceeded those of other countries or regions (Table 1.2.7). The combined number of cited core papers of the Chinese Academy of Sciences and the University of the Chinese

《Table 1.2.5》

Table 1.2.5 Countries or regions with the greatest output of core papers on the “CRISPR/Cas9 genome editing in agricultural biotechnology”

《Table 1.2.6》

Table 1.2.6 Institutions with the greatest output of core papers on the “CRISPR/Cas9 genome editing in agricultural biotechnology”

Academy of Sciences approached 900, whereas the citation rate of the core papers exceeded 40% (Table 1.2.8).

An in-depth analysis of supporting data revealed that 40 papers were cited more than 200 times, of which eight papers were cited more than 500 times. The article “Genome engineering using the CRISPR/Cas9 system” published in 2013 in Nature Protocols was cited more than 1900 times. Also, the paper entitled “Development and applications of CRISPR/ Cas9 for genome engineering” published in 2014 in Cell was cited nearly 1600 times. These two articles laid the foundation for the CRISPR/Cas9 system to become the leading gene- editing technology. At present, the CRISPR/Cas9 technology is widely applied in genomes of organisms such as humans, Arabidopsis, yeast, mice and fruit flies. Also, it has been

《Figure 1.2.3》

Figure 1.2.3 Collaboration network among major countries in the engineering research front of “CRISPR/Cas9 genome editing in agricultural biotechnology”

《Figure 1.2.4》

Figure 1.2.4 Collaboration network among major institutions in the engineering research front of “CRISPR/Cas9 genome editing in agricultural biotechnology”

《Table 1.2.7》

Table 1.2.7 Countries or regions with the greatest output of citing papers on the “CRISPR/Cas9 genome editing in agricultural biotechnology”

《Table 1.2.8》

Table 1.2.8 Institutions with the greatest output of citing papers on the “CRISPR/Cas9 genome editing in agricultural biotechnology”

successfully used in the genomes of economically important animals, including cattle, pigs and sheep as well as important crops, such as wheat, sorghum, rice and maize, thus achieving targeted genome editing. The analysis of high-frequency words revealed that CRISPR/Cas9, TALENs, and microbial population were the front areas of scientific research.

1.2.3 Intelligent agricultural equipment

The development of intelligent agricultural equipment control technology focuses on the development and expansion of various information technologies, including sensors, communication systems, image-processing systems and computer vision. For this research front there are four major research areas. (1) Specialized sensors: research on new principles, methods, and technology for agricultural sensors; the theory and technology of multi- sensor information fusion and measurement; and agricultural sensor networks. (2) Agricultural bioinstruments: research and development of animal and plant bioinformation monitoring sensors and devices; precision breeding equipment and information technology products; and animal and plant microphysiological-information testing equipment. (3) Intelligent agricultural machinery: research on precise variable-rate control, navigation, and real-time operation-monitoring technologies. The development of agricultural intelligent equipment that supports precise farming operations. (4) Agricultural robots: research on bionic principles; design of fundamental components; optimization paths; intelligent control; and decision-support algorithms.

The development of model robotic-systems for farming operations. Research on developments in 2017 revealed that most of the patents that are related to the present study came from China and the USA. China accounted for about 75% of all patents, while the USA accounted for less than 25%. However, the ratio of patent citations is just the opposite, indicating that despite having fewer patents, the USA had a significant influence in this area. In terms of contributing institutions, Hunter Industries (USA) and China Agricultural University were the major contributors to patents. Also, USA and Canadian institutions collaborated significantly. At present, while the existing equipment meets the agricultural needs at various levels, further research and development are required. Future research directions are expected to include digital design, simulation systems and testing platforms of intelligent equipment; agricultural sensors, agricultural robots and navigation control technology with microelectromechanical systems; and the integration of advanced information technology (such as the Internet of Things, big data, cloud computing and cloud services) into the design of intelligent agricultural equipment.

An analysis of relevant academic papers revealed the following. In terms of distribution by country (Table 1.2.9), the majority of core articles was contributed by China and the USA. Although the contribution of core papers from Spain was less than half that from China, it ranked first with respect to the number of cited papers. In terms of research institutions (Table 1.2.10), the distribution of core papers was relatively randomly distributed, with no particularly strong contributors.

The country collaboration diagram (Figure 1.2.5) reveals that there was frequent collaboration between the USA and China as well as the USA and India. In addition, Spain and Italy also collaborated closely. The institution collaboration diagram (Figure 1.2.6) shows that only the University of Sydney (Australia) and the University of São Paulo (Brazil) collaborated closely. China ranked first in terms of the number of core papers contributed in this research direction. However, it ranked only fifth in terms of the number of cited papers and its average citation rates also lagged behind those of other countries (Table 1.2.11). The Chinese Academy of Sciences was the largest contributor of cited core papers (Table 1.2.12).

An in-depth analysis of supporting data revealed that Chinese scientists produced more research papers on intelligent agricultural equipment than in other areas. In addition, the number of conference papers was also relatively high. A high- frequency keyword analysis revealed that unmanned aerial vehicle, system integration and precision farming were the fronts on interest by the scientific community in this field.

《2 Engineering development fronts》

2 Engineering development fronts

《2.1 Development trends in the top 10 engineering development fronts》

2.1 Development trends in the top 10 engineering development fronts

The top 10 engineering development fronts assessed by the field of agricultural engineering research are classified into the following three categories.

Ground breaking development front: “utilization technology

《Table 1.2.9》

Table 1.2.9 Countries or regions with the greatest output of core papers on the “intelligent agricultural equipment”

《Table 1.2.10》

Table 1.2.10 Institutions with the greatest output of core papers on the “intelligent agricultural equipment”

《Table 1.2.11》

Table 1.2.11 Countries or regions with the greatest output of citing papers on the “intelligent agricultural equipment”

《Table 1.2.12》

Table 1.2.12 Institutes with the greatest output of citing papers on the “intelligent agricultural equipment”

《Figure 1.2.5》

Figure 1.2.5 Collaboration network among major countries in the engineering research front of “intelligent agricultural equipment”

of animal stem cell” of veterinary science, “crop transgenic technology” of crop science, and “animal models and animal genome editing” of veterinary science.

Newly emerging development fronts: “agricultural waste and biomass energy conversion” of agricultural engineering, “efficient utilization of solar energy in agricultural facilities” of agricultural engineering, and “development and utilization of intelligent agricultural machinery” of agricultural engineering.

In-depth established development fronts: “development of high-efficiency, low-toxicity disease control compounds for agricultural use” of plant protection science, “introduction of disease-resistant genes and utilization of new disease- resistant varieties” plant protection science, “forestry information database and ecosystem construction” of

《Figure 1.2.6》

Figure 1.2.6 Collaboration network among major institutions in the engineering research front of “intelligent agricultural equipment”

forestry science, and “breeding of inbred lines and new hybrid varieties of crops” of crop science.

“Crop transgenic technology” had the highest number of patents, reaching 738. The average number of patents was around 310 patents. The article “animal models and animal genome editing” had the highest average number of patent citations, reaching about 33. Important research-area patents averaged 17 citations. A list of the highest average number of patents was published in May 2013 (Table 2.1.1). The average number of patents for all important research fronts showed a steadily decreasing trend year after year (Table 2.1.2).

Top 10 engineering development fronts are summarized below.

(1)  Utilization technology of animal stem cell

This technology is a ground breaking development front in the field of veterinary medical science. Animal stem cells are a type of self-renewing pluripotent cells. Under certain conditions, stem cells can be separated into different types of functional cells. Based on their developmental stage, stem cells can be divided into embryonic stem cells and somatic stem cells. Based on their differentiation potential, stem cells can be divided into three types: totipotent stem cells, pluripotent stem cells, and unipotent stem cells. Stem cells are a type of immature, undifferentiated cells that have the potential to regenerate various tissues and organs of the human body. In the medical field, these cells are known as all-

《Table 2.1.1》

Table 2.1.1 Top 10 engineering development fronts in agriculture

《Table 2.1.2》

Table 2.1.2 Annual number of core patents published for the top 10 engineering development fronts in agriculture