2 Construction of Maize DNA Fingerprint Library
2. 1 Construction of Maize DNA Fingerprint Library Using SSR Molecular Markers
At present, the genetic markers adopted for the identification of maize germplasm at home and abroad are still mainly morphological markers, with reference to isoenzymes and seed storage protein markers. However, the performance of morphological markers is greatly influenced by the environment, the identification workload is large, the cycle is long, and the season is limited. Isozymes and seed storage protein markers are not sufficiently polymorphic, isozymes still exist tissue and organ specificity, and there are strict conformity requirements, so the identification results are not stable enough. The rapid development of molecular markers in recent years is a genetic marker based on the polymorphism of DNA molecules, which can be stably inherited and can reflect individual and population characteristics of organisms. Because it directly reflects the differences in DNA levels, with a high degree of specificity and specificity, DNA fingerprints obtained by different species, the same species and different species, as human fingerprints, become the most advanced fingerprint identification technology. An ideal molecular marker should have the following characteristics: high polymorphism; good reproducibility and stability; clear band type, easy statistics; uniform distribution on the chromosome, neutrality, codominance, simple and rapid, easy automation; And the use of low cost. The rapid development of DNA fingerprinting technology, in addition to the RFLP based on Southern hybridization, a number of new DNA fingerprinting technologies based on PCR have been developed in recent years, such as RAPD, AFLP, SSR, SCAR and ISSR. SNP-based SNP technology. However, different molecular markers have different application values ​​(Yuan Lixing et al., 2000; Saliba-(Mombani et al., 2000). RFLP techniques have low polymorphisms, limited genetic information, large amounts of DNA templates, and complicated operations. Although RAPD technology has the advantages of simplicity, low DNA, high degree of automation, and short experimental period, it is sensitive to reaction conditions and has poor reproducibility.AFLP has the advantages of high polymorphism and good stability, but the required DNA template large, complicated steps, while it is patented technology. compared with other markers, microsatellite sequences to SSR markers based on DNA fingerprinting construct a display library abundance .SSR marker unique advantages, covering the entire genome , The revealed polymorphism is high; has the characteristics of multiple alleles, provides a large amount of information; inherited in the Mendelian way, is co-dominant; each site is determined by the designed primer sequence, which facilitates the interaction between different laboratories Collaborative development of primers allows the data obtained to be replicated and shared in different laboratories (Li Xinhai et al., 2000). Although the development costs of SSR primers are quite high, they are huge With potential applications, the development of SSR primers in some major crops is under way.At present, there are more than 1,800 pairs of SSR primers already published on maize, and new primers are added at regular intervals for the technology in maize. The application of DNA fingerprinting provides good conditions.
2.2 The significance of the construction of maize DNA fingerprinting database and its role
The national germplasm bank of China has collected 15967 corn germplasms. About 300 corn hybrids with an area of ​​more than 50,000 mu are planted every year on the production. More than 1,000 maize hybrids and inbred lines have been applied for protection of new plant varieties. Each year, it participates in national regional trials and pre-tested by provinces and cities in thousands of varieties, and has passed hundreds of national and provincial certifications (Sun Shixian et al., 2005). At the same time, due to the concentration of the parent application backbone few genetic differences between maize varieties getting smaller and smaller, combined with the application of new technologies such as genetically modified corn breeding, based on the original breed improvement on only a few or even a single trait of dependency derived varieties Will increase. The above aspects factors make completely maize varieties increasingly difficult to distinguish based on morphological characters, to the variety of resources to collect, collate, screening and identification of breeding varieties, protection and development of seed corn production, operation, management, rights, etc. All links bring varying degrees of difficulty. In view of the above-mentioned problems, it is urgently necessary to give every corn hybrid and inbred line from the molecular level of DNA with an identity card number that can accurately indicate its identity. Compared with the traditional methods of morphological and protein electrophoresis, DNA marker technology can reveal more polymorphisms, but also accurate and reliable, simple and quick and easy advantage of automation, which is a prerequisite to achieve the industrialization of species identification, but also the variety Identify the development trend of technology.
2.2.1 Identification and protection of corn varieties
There are a large number of polymorphic markers in each species in the same species, and a unique marker that has a different species from other species, that is, a combination of specific DNA fragments, is called a “fingerprint†of the species, and a unique fingerprint of each species. The fragments constitute the DNA fingerprint library of the species, which has a high degree of individual specificity and stability similar to human fingerprints. The DNA fingerprinting database has a wide range of applications in crop breeding: first, the difference in DNA fingerprints of each species can directly provide information on the DNA level related to the target traits, avoiding environmental disturbances, and thus greatly improving the parent breeding in hybrid breeding. The latter agent wanted the selection efficiency of the single plant; second, it could effectively identify the purity and authenticity of the variety, as well as the registration of new varieties and intellectual property protection of the variety, by testing whether the variety had the distinctive mark fingerprint fragments of the variety. Research conducted maize varieties of standard DNA fingerprint library in existing fingerprint technologies and applications built on the basis of DNA, which improve seed quality seed market is important for the interests of protecting intellectual property rights and breeders bred varieties of corn.
2.2.2 purity and authenticity detection
In the process of production and sales of corn hybrids, the establishment of quality seed testing as a center of breed breeding and seed management system plays an important role in stabilizing and popularizing fine varieties. In the international standards and national standards, the seed quality is measured and graded using the seed purity, cleanliness, germination rate and moisture quality characteristics. Of these four indicators, the purity of the species is the most important. At present, the purity identification of maize seeds in China is still based on morphological identification, seedling identification and field plot identification, supplemented by isozyme and protein electrophoresis. However, the number of maize varieties is increasing, and the germplasm foundation is becoming more and more narrow. The original detection methods can no longer meet actual needs. In practice, new detection technologies are urgently needed. DNA fingerprinting technology adapts to this need because of its high resolution, good repeatability, and simplicity and speed.
2.2.3 National District Test Quality Monitoring
DNA fingerprinting technology is mainly used in the following three aspects in the national regional test:
(1) Conformance testing of test combinations. If the test portfolio itself does not have consistency, it loses the most basic condition as a breed, cannot be called a breed, and of course there is no need for a district test. In practice, some breeders may use early-maturing combinations that are not completely homozygous in order to introduce varieties as soon as possible. Such combinations are not yet stable in several traits and should not be promoted in production. If such combinations can be eliminated before or early in the district test, many unnecessary tasks will be reduced and limited resources will be concentrated on promising combinations. The use of morphological traits to detect long-term (at least one growing season) does not play a pre-control role, and only DNA fingerprinting technology can do this.
(2) Whether the monitoring combination will be replaced in different district test years. In practice, some breeders do not have a very prominent combination of performances in the first year of the regional test. In the second year of the regional test, they are replaced by another combination. In many cases, the two combinations have a common parent or close relationship, so the differences in morphological traits are less obvious and difficult to distinguish. How to prevent this from happening and ensure the fairness and seriousness of the district test is one of the important issues faced in the district trial work. The high discrimination ability of DNA fingerprinting technology has been adapted to this need.
(3) Test for variety rights at the same time as the district test. There is a close relationship between regional testing of varieties and testing of variety rights, and the two are complementary. However, at present, the domestic status quo is that the variety right test and the regional test are conducted separately, and they have no relationship with each other, resulting in huge waste of human and material resources. Some experts suggested that the two should be combined organically and simultaneously so that a set of tests meet the requirements of both goals (Sun Shixian et al., 2003). However, how to operate in a specific job is still a question worthy of further discussion. The use of DNA fingerprinting technology to test the variety rights of regional test varieties provides a feasible implementation. In 2002, 54 DNA fingerprints of regional trials in Beijing, Tianjin, Tangshan, and Huanghuaihai districts were initially constructed; in 2003, 11 district trials in Beijing, Tianjin, Tangshan, and Huanghuaihai regions were tested for consistency in the second year regional trials. The DNA fingerprints of the same variety of two-year regional test were compared (Zhao et al., 2003).Replacement Parts For Great Plains/ Great Plains Parts
Our Replacement for Cornheader Parts is good in quality and competitive in price. We are manufacturer and supplier of Replacement for Cornheader Parts following your specific requirement. We are looking forward to your E-mail and establishing cooperative relationship with you! We would provide professional Replacement for Cornheader Parts with good services for you!
Replacement Parts for Great Plains manufacturer & supplier, offer different kinds of Great Plains Drill Parts, Great Plains Planter Parts for customers.Please contact us!
Replacement Parts for Great Plains
Replacement Parts For Great Plains,Great Plains Drill Parts,Great Plains Planter Parts,Great Plains Parts
Ningbo Borine Machinery Co.,Ltd. , https://www.borine-agroparts.com