Application Of DNA Barcode And EDNA Technology In Fish Classification And Identification

With the rapid development of DNA barcode and eDNA technology,more and more fields have begun to apply these two technologies.Similarities are also different for different fields or research directions,under the same principle basis,its technical route,method flow,data analysis,etc.Based on DNA barcode technology,this dissertation first carried out the research on the species composition of commercial salmon products and the research on theDNA taxonomy of flatfish.Then,the optimization of eDNA technology and its application in fish diversity in artificial breeding environment were discussed.In summary,this article conducts research and discussion on the application of the two technologies in practice,and analyzes the advantages and disadvantages of their operations.1."Salmon" is the collective term for salmon and trout,and is an internationally recognized high-end aquatic product.Salmon in European and American cultures usually refers to Atlantic salmon(Salmo salar)that has a trans-salinity parade behavior.In recent years,due to the large number of freshwater farmed rainbow trout(Oncorhynchus mykiss)on the market,it is often referred to as "salmon",which has aroused fierce debates about "true and false salmon species".For ordinary consumers without taxonomy knowledge,it is difficult to judge the types of salmon circulating in the aquatic product market and whether the product labels are authentic.In this study,samples and surveys of salmon products in large supermarkets and farmer markets in six urban areas of Qingdao were carried out,and a DNA barcode classification and identification study was carried out on the samples.In this study,samples and surveys of salmon products in large supermarkets and farmer markets in six urban areas of Qingdao were carried out,and a DNA barcode classification and identification study was carried out on the samples.The results showed that among the 74 salmon samples collected,61 samples were Atlantic salmon(Salmo salar),accounting for 82.43%;11samples were rainbow trout(Oncorhynchus mykiss),accounting for 14.86.%;It also contains 1.35% of Oncorhynchus kisutch and Oncorhynchus keta.Although the survey data shows that the salmon products circulating in the Qingdao market are mainly Atlantic salmon,a comparison of the product identification and the actual species information found that 14.86% of the salmon outer packaging identification product names are inconsistent with the test results,and more than 40% of the salmon products are not labeled Origin information.It can be seen that salmon aquatic products still have a certain risk of adulteration and food safety.It is recommended that relevant departments should formulate product standards and testing standards as soon as possible to ensure that the quality and safety of salmon aquatic products can be traced.At the same time,it shows that the identification of aquatic products based on DNA bar code technology is feasible and efficient.Based on this,relevant aquatic product identification methods can be established,which can effectively shorten the identification time.2.DNA barcoding,which is widely used in taxonomic research,provides strong technical support for rapid and accurate identification of species.Pleuronectiformes is an important economic fish,and it is also an important existence of energy conversion and material circulation in water ecosystem.At the same time,Pleuronectiformes is the only group of vertebrates with asymmetric adult morphology on both sides.With the growth and development of some species,the body surface characteristics of juveniles will gradually disappear,so there is a big difference between them and adults.At present,the identification of adult Pleuronectiformes is mainly based on the characteristics of bones and body stripes,but these characteristics may change with the change of environment and other factors,which brings some obstacles to the morphological identification of Pleuronectiformes.Therefore,we hope to use molecular methods to classify Pleuronectiformes,so as to avoid the obstacles of morphological classification and bring another solution to the classification of Pleuronectiformes.In this study,a total of 160 self-test samples,belonging to 8families,11 genera and 16 species,and 333 species,132 genera and 13 families,were downloaded from NCBI database.The genetic distance and phylogenetic tree were calculated by mega 6.0 software.In this study,we found that the interspecific distance within genera,within genera and within families,and the genetic distance between orders increased with the increase of taxon;through the establishment of phylogenetic tree,we found that the clustering of genera and families produced a mixed phenomenon,which indicated that the genetic distance based on genes was different Bar code classification is more suitable for species identification and classification of lower taxonomic mediators and a small range.For higher level phylogenetic analysis,it is not completely reliable to rely on a single 600 + gene fragment for phylogenetic analysis,but it can be used as an aid for morphological species identification or selection,and it can be used to match with DNA bar code and morphological classification of other target genes for a certain species Taxonomic mediators are used for more complete and in-depth phylogenetic studies.3.DNA barcode technology combined with environmental DNA method has become a new method of biodiversity investigation,and has been improved and developed in the continuous application research.This part is based on the fish 12 s region general primer mifish-u to detect the diversity composition of fish species in the underwater world tunnel water body of Qingdao city.The different filtration volume gradient is set,the amplification efficiency of target primer is analyzed and the data between parallel samples are observed to analyze the detection of target species under various conditions.In five filtration gradients,the detection rate of target species is not large,but the number of sequence of detected species decreases with the decrease of filter water volume;the data consistency between the parallel samples of the same gradient is low,and the number of detected species and reads is different;through the determination of the matching rate of the target primer,it is found that the matching results are basically the same as the final detection results.Mifish-U primer pairs are basically the same the results showed that the results of the test were good,and the generality of chondrofish was not good.The data of snapper in this study were analyzed.The OTU sequences corresponding to the same species were screened manually,and the qualified sequences were selected for genetic distance calculation.It was concluded that the primer had good identification ability for the same genus and related species.This article analyzes and studies the actual effects and existing problems of the Mifish-U primers in the application process,in order to provide relevant reference and theoretical support for the application of the primers and the application of environmental DNA methods in the later period.