Analysis Of Genetic Relationship And Comparison Of Umami Substances Of Meretrix Meretrix From Different Populations

Meretrix meretrix has been farmed since a thousand years ago, it is one of the important economic shellfish in our country with high economic value, rich nutrition and delicious meat. In recent years, due to the fact that a large number of wild Meretrix meretrix fingerlings were captured and cultured in different places, gene flow of Meretrix meretrix populations with different genetic background was artificially increased, it had a greater negative impact to germplasm resources conservation. Therefore, genetic relationship of six Meretrix meretrix populations from different areas was analyzed by three molecular biology methods in this paper. In addition, umami substances of Meretrix meretrix from Jiangsu with two kinds of shell color and the offspring of red shell color were quantitatively detected to provide reference for Meretrix meretrix breeding.In this paper, 18 S ribosomal RNA gene, mitochondrial cytochrome oxidase c subunit I(COI) gene and 16 S r RNA gene sequences of six different Meretrix meretrix populations from Liaodong Peninsula sea area(Liaoning population), Yangtze estuary and its two wings sea area(Jiangsu population), Western sea area of Taiwan Strait(Fujian population), Pearl River estuary and its two wings sea area(Guangdong population), Beibu Bay sea area(Guangxi population) and Ise Bay sea area, Japan(Mie population) were sequenced and analyzed to study their genetic relationship. The genetic background of different Meretrix meretrix populations was understood in molecular level, to provide theoretical basis for germplasm resources research and breeding. The results of sequence analysis showed that: the length of three genetic sequences was about 1854 bp, 658 bp and 596 bp respectively; base composition of 18 S r RNA gene was unbiased, and its sequence was conservative; A+T content was obviously higher than G+C content in both COI and 16 S r RNA gene, which was in accordance with features of mitochondrial genes. Gene sequences of six Meretrix meretrix populations were aligned by Meg Align, the percentage of sequence identity was 99.7%-100.0%(18S), 91.7%-99.8%(COI), 90.2%-99.8%(16S) respectively, Meretrix meretrix from Mie had the largest difference. Phylogenetic trees were constructed by MEGA5.03 using adjacent connection method(NJ) with Meretrix lyrata as outgroup. Five Meretrix meretrix populations from China coast areas were clustered into one clade and separated from Meretrix meretrix from Mie, Japan, bootstrapping value was 67%(18S), 99%(COI) and 98%(16S) respectively; among the five populations from China coast areas, Meretrix meretrix from Liaoning, Jiangsu, Fujian were clustered together first, and then the population from Guangxi, the last was the population from Guangdong. Results indicated that: Meretrix meretrix from Liaoning, Jiangsu, Fujian had a higher homology and their genetic relationship was the closest; a larger genetic difference was found among Meretrix meretrix from Guangxi, Guangdong and other populations from China, and their geographic genetic differentiation was obvious; Meretrix meretrix from Mie, Japan and China coast areas could be described as two geographic subspecies.Meretrix meretrix from Jiangsu were focused on in this study, protospecies populations of red shell color, yellow shell color and F1, F2 populations of the red shell color were collected to detect the main non-volatile flavor substances components. Contents of nucleotides(AMP, GMP, IMP), succinic acid, free amino acids, inorganic ions(Na+, K+, Cl-, PO43-) were learned and their flavor roles were evaluated by taste intensity value(TAV). In view of the synergies of nucleotides and amino acids in terms of flavor, Equivalent Umami Concentration(EUC) was used to evaluate the quality of flavor of different Meretrix meretrix populations. Results showed that, the TAV value of AMP, succinic acid, Glu, Arg, Ala, Na+, K+, Cl- was greater than 1, so they were the major flavor contributors of Meretrix meretrix; protospecies populations of red shell color had the maximum flavor intensity(4.92 g·100g-1), then its progeny F1(4.08 g·100g-1) and F2(4.09 g·100g-1) were slightly lower, but still significantly higher than protospecies populations of yellow shell color(3.34 g·100g-1)(P<0.05), indicated that Meretrix meretrix populations of red shell color from Jiangsu had a relatively stable high quality in terms of flavor. This article provided theoretical basis for breeding and application in seasoning products development of Meretrix meretrix.