Construction Of SSR Fingerprint And Analysis Of Genetic Diversity Of Economic Varieties Of Main Silkworm In Sichuan And Chongqing Area

As an important economic animal, silkworm in different ecological conditions over a long period of time gradually formed many geographic strains. The traditional classification method of silkworm mainly based on economic traits and morphological characters, but the economic traits are greatly affected by environment, while it is hard to distinguish the morphological characters accurately for a smaller difference of varieties.Microsatellite DNA (SSR) is a nucleotide sequence, which takes1-6nucleotides as a unit, by tandem repeats, length up to tens or even hundreds of nucleotides, and widely distributed in the genome of eucaryote. Now SSR has already widely used in construction of molecular genetic map, identification of germplasm resource, analysis of genetic diversity, gene location, QTL mapping and cloning and auxiliary selection of molecular marker, etc.The silkworm germplasm resource DNA fingerprint using SSR marker, it can provide a convenient method for the selection of varieties, for breeding silkworm with recessive gene and creating silkworm varieties with special characters, it can improve the accuracy of artificial selection process, shorten the variety breeding cycle, and provide scientific evidence for the identification, genetic evaluation and utilization of silkworm.In this study, it takes14kinds of main silkworm varieties in Sichuan and Chongqing area as materials, using polyacrylamide gel electrophoresis to analyze PCR product, and silver staining, studies on silkworm microsatellite polymorphism, the main research results are as follows:1.26pairs of SSR primers with better polymorphism were selected from36pairs, as follows:S1502, S1503, S1504, S1507, S1508, S1509, S1514, S1515, S1516, S0201, S0213, S0214, S0216, S0217, S0218, S0219, S0220, S0222, S0223, S1117, S1405, S0301, S0302, S0303, S0305, S0307.2. Using26pairs of primers to amplify the genomic DNA of14silkworm varieties, and obtaining341SSR loci, polymorphic loci is327, polymorphism rate is95.89%, per pair of primer has13.12bands, the average polymorphism ratio is94.91%, it turned out that SSSR polymorphism is quite abundant.3. UPGMA cluster analysis showed that, the genetic similarity of14silkworm varieties (GS) is between0.49-0.83. Takes the GS0.6as the boundary, the samples are divided into two kinds:Qiubai, Xian2,854B, Xianghui,872A,7532,872B are clustered into one group;871B,871A, Qiufeng, Xian1, Xiafang, Furong,932together as another class. This result is inconsistent with the strain which variety belongs to.4. Analysis results of PCA are inconsistent with the UPGMA cluster analysis results.5. According to the results of cluster analysis, selected17pairs of core primers: S1502, S1503, S1504, S1508, S1509, S1514, S1515, S1516, S0201, S0213, S0214, S0216, S0217, S0219, S0301, S0302, S0303. The results of core primers amplification can separate the14silkworm cultivars, and use these17pairs of primers to construct silkworm DNA fingerprint digital map.