Application of Plant Genomics Theory and Methods
Crop germplasm resources are the basis for crop breeding. Its discovery and use have triggered a world-renowned "green revolution" in the 1950s and 1960s. However, since the 1980s, the level of crop breeding has not made great progress due to the huge increase in the number of copies of the quality of resources collected and stored, but there has been a stagnant situation. The analysis found that this was mainly due to the narrow genetic base of the breeding parents. Therefore, how to efficiently and continuously exploit and utilize the best genes in germplasm resources is an important scientific problem that is urgently needed to be solved. The creation of genomics has created an opportunity to solve this scientific problem. At the same time, the competition for germplasm resources has become more intense at the genetic level and a world-wide "gene wars" has begun. The article reviewed how plant genomics can promote gene research and development of germplasm resources, and put forward strategies and recommendations for exploring excellent genes in China's rich crop germplasm resources.
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Crop germplasm is the carrier of genes controlling crop traits. Therefore, crop germplasm resources are also called gene resources. Crop breeding is actually the selection and combination of genes in crop germplasm resources. There is no crop breeding for crop germplasm resources. Therefore, crop germplasm resources are the material basis for crop breeding and related disciplines. The development and utilization of some excellent genes in crop germplasm resources can lead to breakthroughs in crop yields. For example, the first "green revolution" was triggered by the development and utilization of a few dwarf genes in wheat and rice resources. China's hybrid rice has achieved great success, and the discovery and application of wild rice resources play a key role.
Because crop germplasm resources play such an important role in crop breeding and other related research fields, governments and scientists all over the world attach great importance to the collection and preservation of crop germplasm resources. There are as many as 6.1 million (including duplicates) of quality resources, of which the three countries with the highest collection and preservation are: 410,000 in the United States, 370,000 in Russia, and 360,000 in China. However, the progress of crop breeding has not made significant progress due to the huge increase in the number of crop germplasm resources collected and preserved. In contrast, crop breeding in many countries in China and in the world has stagnated in the past 80 years. Analysing the causes of this phenomenon, scientists generally recognized that this is mainly due to the narrow genetic base of breeding parents (Eniqun et al., 1996). This means that although the collection and preservation of germplasm resources in various countries is very rich, the germplasm resources used for crop breeding are very poor. How to solve this sharp contradiction, that is how to quickly and accurately identify new and outstanding genes that are urgently needed in breeding from rich germplasm resources, will become an urgent need for the current crop germplasm resources and crop breeding in the world. Scientific question.
Plant Genomics provides a new theory and method for gene research on crop germplasm resources Genomics is a new discipline that has been developed on the basis of the genome project in recent years. The main research content of genomics is biology. The structure and function of the genome is therefore a science that studies the nature of life phenomena. Genomic research is considered to be one of the most important scientific research plans in this century. Its investment intensity is high. There are many scientific and technological personnel involved and the impact is wide. Some people even compare it with the current atomic bomb program and current space program. This is collectively referred to as this century. Three international scientific research programs. The Plant Genome Project is an important part of the genome project. At present, the major plant genomes in the world include the Arabidopsis genome project, the rice genome project, the wheat genome project, and the maize genome project. The plant genome project has made great progress in recent years, resulting in a series of theories and methods, which has developed into a new discipline, plant genomics. The main progress of the plant genome project in recent years is summarized in the following five main points:
1. Discovered a series of molecular markers,
2. A high-density genetic map of rice, wheat, corn, and other major crops was mapped, along with the physical map of rice, to complete the work that had not been completed in the past decades.
3. Many important agronomic traits were mapped, mapped and tagged.
4. The conservation of genomes between Gramineae crops and rearrangement of nonhomologous homologous chromosomes were found.
5. A new method for cloning genes was proposed and a number of new genes were cloned.
6. The structural homology or conservation of different disease resistance genes in plants was found. These above-mentioned theories are the in-depth research of crop germplasm resources, especially the identification and excavation of genes has given a huge impetus.
1. Provide a quick and effective new method for the construction of crop core collections.
Core germplasm is also called core corllection. This concept was proposed by the Australian scientist Frankel (1984), which refers to the use of the smallest germplasm resources sample to represent the genetic diversity of germplasm resources to the greatest extent. Once the concept of core germplasm was proposed, it immediately received the attention of scientific researchers from all countries in the world. However, scientists from different countries have different views on how to build core germplasm. Some people proposed to build core germplasm according to the place of production; it was proposed that the core germplasm should be constructed according to the classification system, and it was proposed that the core germplasm be constructed according to the traits. Molecular markers are a technique that directly reflects the genetic diversity of germplasm resources at the DNA level. It has the advantage of high polymorphism in the marker locus and is therefore a powerful tool for studying the core germplasm. At present, many countries in the world are using this new method to build core collections.
2. Promoting germplasm research into the “phenotype of germplasm in the new era of genotyping†refers to the morphology of germplasm, such as the height of the plant, the early and late stages of maturity, resistance to disease or disease, etc. The genotype of germplasm refers to the number of genes controlling the traits in the germplasm, the recessive, homozygous or heterozygous, etc. The phenotype of the germplasm is not only influenced by external environmental conditions, but also often As a result of multiple genes acting together, the phenotype cannot reflect the genotype.The identification of past germplasm resources is basically limited to phenotype identification, although phenotype identification is very necessary for the study of germplasm resources, it is obviously not Only through a clear understanding of the genes carried by germplasm resources can they be developed economically and efficiently, and genomics research provides new theories and methods for genotyping of germplasm resources. The genetic linkage maps of the crops that have already been drawn can find the target genes that people are interested in in a relatively short period of time. Currently, there are a number of important agronomic characteristics in various major crops. Genes are mapped and mapped. What is particularly needed are many important agronomic traits, such as yield traits, stress resistance, etc. are all quantitative traits, and it is difficult and invasive to study these traits using traditional methods, using molecular markers. Marking technology can be used to study quantitative trait loci (QTLs) as well as qualitative trait loci. At present, many important researches have been made in this method, such as 1000-grain weight, spikelet number and plant height. The important QTLs for heading date, tiller number, panicle number, etc. of wheat have been reported.
Molecular mapping can not only locate and map known genes quickly and accurately, but also has a particularly important role in the identification and discovery of new genes. According to the concept of traditional germplasm resources identification, only the germplasm resources with good phenotypic traits will have excellent agronomic traits, that is, high-yielding genes will appear in high-producing germplasm resources, showing resistance to disease. Only disease-resistance genes can be found in quality resources. However, this traditional concept has been strongly impacted in recent years. Bernacchi (1996) reported that using tomato's wild species Lycopersicon hirsutum to improve tomato varieties can increase the yield, soluble dry matter content and fruit color of tomato varieties by 48%, 22% and 33%, respectively. According to reports, in the wild rice Oriza. rufipogon, two QTL loci have also been found to increase the hybrid hybrid yield by 17%, and similar results were obtained in experiments in South Korea and Colombia. In fact, these results have already been reported, but did not attract people's attention. For example, Feldman reported in 1993 that the use of common wheat and two wheats crossed and backcrossed, in the offspring it was possible to select a strain with a 19% increase in yield over the popular variety. In our laboratory, we crossed the wheat with the rough goatgrass and backcrossed with wheat. In the offspring, we also selected a strain with a double number of ears per ear (Kong Lingrang, 1996).
The above findings are a challenge to the traditional concept of identifying and evaluating germplasm resources. That is to say, the evaluation of germplasm resources only from phenotypic traits, especially the evaluation of quantitative traits, is incomplete. The result will be that some genes carrying valuable genes Germplasm resources are buried, and it is these germplasm resources that carry new genes that have not yet been exploited. The development and use of these genes will likely lead to breakthroughs in breeding. From this, it can be seen that the genotype identification of germplasm resources will lead to the discovery of many new genes that have not yet been developed. This will greatly broaden the material basis for crop breeding and make breakthroughs in crop breeding.
3. The research of the GKM has avoided the new way for gene cloning to clone the gene of interest with important economic value and scientific research value from the plant genome, and then use genetic engineering to transfer it to another species or variety. Research on its structure and function is a research direction that genetic workers have longed for and diligently pursue.
The method of cloning genes was usually based on the product of a gene, a protein sequence. However, since the products of most genes are unknown, the genes cloned using this method are very limited. The development of genomics has opened up new avenues for gene cloning. Based on the position of the target gene in the genetic map and physical map of the chromosome, chromosome cloning was used to clone the gene, known as map-based cloning. Using this method, people have successfully cloned important agronomic trait genes such as Xa21, a rice bacterial blight resistance gene. In recent years, during the process of cloning genes, it was found that the sequences of similar genes among different crops are strikingly similar, so that according to the sequence of a disease-resistant gene of a crop, it is possible to clone different disease-resistance genes from another crop. . There are other methods for assisting the above two cloned genes, such as differnt dasplay and genenonic snbstractive methods, which were also invented and used for gene cloning. It is worth mentioning that the whole genome sequencing work of Arabidopsis and rice is currently completed in the near future, and hundreds of millions of DNA sequence data will be generated. In order to analyze the structure and function of these genomic DNA sequences, a new discipline, Bioniformatics, has emerged. The application of bioinformatics principles and methods to the analysis of large datasets for genome sequencing will expedite the speed of gene cloning and will eventually clarify the entire genome of the plant genome.
The development of genomics makes the competition of germplasm resources more intense. Crop germplasm resources mainly serve the crop breeding. In the past, the depth of research on germplasm resources was insufficient, and the backwardness of breeding methods also affected the development and utilization of germplasm resources. With the promotion and promotion of genomics, a new breeding method, molecular breeding, has been born. There are two types of molecular breeding, one is molecular marker-assisted breeding, also known as "maker assisted selection." It is a breeding method for selecting breeding progeny based on molecular markers of target traits. Since molecular markers are not affected by environmental components, the use of this method can increase the accuracy of selection, shorten the breeding cycle, and accelerate the breeding process. It has been estimated that the use of molecular marker-assisted breeding can reduce the breeding cycle from 6-7 years to 2-3 years, and the efficiency of selection can be increased several times.
Another type of molecular breeding is transgenic breeding (also called genetic engineering breeding). It is a series of steps for constructing a vector and transforming a target gene isolated from a clone, and then transferring it into another plant or variety to express it in a new vector variety. Because molecular breeding has the characteristics of short cycle, quick effect, high technical content, and huge economic benefits, the world is currently forming a biotechnology industry with resources as the foundation, genes as the core, and variety as the carrier. The key to molecular breeding is to identify and isolate valuable genes of interest from crop germplasm resources. This is because, on the one hand, molecular breeding can only be performed if there is a target gene; on the other hand, due to the fact that the current germplasm resources have no intellectual property rights, genes isolated from germplasm resources or bred from germplasm resources are bred. The varieties not only have intellectual property rights, but are often pricey. Therefore, at present, all countries in the world have focused their research on gene identification and isolation of germplasm resources and launched fierce competition to form a "gene wars." As the technology for gene identification and cloning has developed rapidly, and the human and financial resources invested by countries in this area are huge, people are expected to be the critical period for the gene war in the next 10-20 years. In this crucial period, who owns the genes, he will have the initiative; if he loses the initiative, he will be punished. In order to win this "gene wars", some developed countries and large transnational corporations in the world have invested heavily in research in this area. In the Americas, the United States and Canada have invested heavily in the study of maize and wheat genes; in Europe, the John Innes Research Center in the UK has received 1-2 million pounds in wheat gene research every year from DuPont; in Asia, Japan, South Korea, etc. Huge investments in rice genetic research; Australian, Australian government invested heavily in the establishment of the Wheat Molecular Breeding Cooperation Research Center, invested tens of millions of dollars each year engaged in wheat molecular breeding research. It is expected that in the next 10-20 years, the international "gene warfare" will intensify. The advantages and problems of gene research on crop germplasm resources in China.
The basis of gene identification and separation of crop germplasm resources is resources. Because even after the genome sequencing of all crops is completed in the future, the genes of various traits can only be separated from the germplasm resources carrying these genes. Possessing rich crop germplasm resources is our greatest advantage in this research field. China is one of the countries with the most abundant crop germplasm resources in the world. At present, more than 300,000 varieties of crop germplasm resources have been collected, ranking second in the world after the United States and Russia. More than 300,000 germplasm resources have been deposited in the country's long-term library, ranking first in the world. There are many very valuable genes in these rich germplasm resources, and only a very small part of the development and utilization has fully demonstrated its important value. For example, the dwarf gene in China's rice genetic resource “low-footed tip†was widely used in the dwarf breeding of rice in the world, and a large number of dwarf varieties were bred; the resistance in China's small family variety Sumai 3 The Fusarium head blight gene is still recognized as the best source of resistance against head blight in the world. It is the best source of resistance to Fusarium head blight breeding at home and abroad; China's wheat landrace China Spring carries 3 pairs of distantly crossed pro- Synthetic genes have been widely used in the distant hybridization of wheat all over the world, and the successful cultivation of distant wheat hybrid materials in the world is almost entirely successful with the “Chinese Springâ€. The anti-cystic disease of soy resources in China plays a key role in soybean disease breeding in the United States, and is considered to be “saving the soybean production in the United Statesâ€. In the current situation where the "new green revolution" at home and abroad is difficult to achieve due to the lack of ideal resources, breeders in countries all over the world are paying more attention to the development of China's crop genetic resources. Rajaram, director of the International Maize and Wheat Improvement Project and an internationally renowned wheat breeder, recently pointed out that the development of China's wheat genetic resources may be an important way for the future of wheat breeding in the world. In recent years, China has paid great attention to in-depth research on germplasm resources and has established a number of important scientific research projects, including the first batch of national key basic research and development planning projects (abbreviated as the 973 project). “The construction of core crop germplasm, important new Research on Gene Exploitation and Effective Utilization"; National Natural Science Foundation of China major project “Study on the identification and excavation of important genes for rice, wheat and cornâ€; National 9th ​​Five-Year Research Project “Molecular Marker Technology Identification Germplasm Resourcesâ€; in the State “863†There are also a number of projects related to genetic markers and gene cloning in the projects and the key and general projects of the Nature Fund, as well as the research projects of provinces, municipalities and departments. In addition, major national science projects for germplasm resources have been brewing for a long time and are expected to start soon. All these have laid the foundation for the in-depth development of China's rich germplasm resources and created favorable conditions.
At the same time, we should also be consciously aware that compared with developed countries, there are still some problems in our research in this area. To sum up, there are mainly the following points:
1. Repeated projects, low investment, molecular markers, and gene cloning are hot research fields at home and abroad in recent years, which have attracted the attention of various general departments. This is a good thing; but due to the multi-headed management of scientific research projects in China, various project management departments Similar projects have been set up. Due to the limited total funding, the investment intensity of each project is insufficient. Therefore, the researchers have to spend a considerable amount of their energies on writing project proposals, project applications, inspection reports, and so on. It will certainly affect the energy of doing research. This phenomenon also exists in other areas of research. Therefore, it is recommended that the project management department conduct division of labor and increase the investment of each project.
2. Long project cycle, scientific research projects have strong timeliness, especially in hot research areas such as genetic research. Some project proposals in China are not proposed more than foreign ones. However, due to the number of project links and the long duration of arguments, they will delay the fight and cause huge losses.
3. Inadequate efforts to attract high-level scientific research personnel. The key to improving scientific research is talents, especially in the field of highly competitive molecular biology research. As domestic investment in molecular biology research has increased in recent years, some domestic laboratories have achieved international advanced hardware construction. The international leading level, however, the research level has not been achieved. The key issue here is the lack of high-level scientific research talents and management talents. According to statistics, the majority of doctoral students engaged in molecular biology research in China have gone abroad. Although the number of Chinese doctoral students or postdoctoral doctors who have returned to China in recent years has increased in foreign countries, the number is small and cannot meet the needs. In particular, fewer international-class talents return home. Therefore, we should further strengthen the work of attracting high-level scientific research talents, and create conditions for high-level scientific research talents from work and life.
The strategy for the basic research of crop germplasm resources in China is based on the experience of foreign gene research on germplasm resources, combined with the advantages of China's crop germplasm resources, and puts forward that “starting from the establishment of core germplasm, we should focus on exploring important agronomic traits in crop germplasm resourcesâ€. Genes, the general idea of ​​cloning a small number of key residues (see the figure below). The 21st century is the century of biotechnology. To a certain extent, the level of biotechnology reflects the comprehensive national strength of a country, and genetic research is the most important research in biotechnology research. One of the contents is that our country has our own unique advantages in this respect. At the same time, there are also some serious deficiencies. Giving full play to our strengths and overcoming our deficiencies, we are sure to hold us in the most important areas of research in this future. Some place.
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