Breeding method of new strain of long oyster with palm heart shape and high meat yield

Abstract

The present application belongs to the field of aquatic animal genetics and breeding, and particularly relates to a breeding method of a new line of palm-shaped and high-meat-yield long oyster. The method comprises the following steps: (1) determining the genetic distance of each population of long oysters from different geographical sources; (2) obtaining the variation coefficient of the shell length and meat yield of long oysters; (3) calculating the genetic force of the shell length and meat yield of long oysters, and the genetic correlation between the two indexes; (4) calculating the family breeding value of the two traits, setting the weight value of the shell length and meat yield respectively, calculating the comprehensive breeding value, and screening the optimal family in proportion; (5) pairing the families among populations to improve the genetic diversity of the offspring; (6) taking the shell length and meat yield as the breeding target, and retaining the seed oysters according to the set seed retention rate every generation, the number of female and male seed oysters is maintained above the set number, and the breeding population retains the matching line.

Description

Technical Field

[0001] The invention belongs to the field of aquatic animal genetic breeding, and in particular relates to a method for breeding a new strain of palm-shaped long oysters with a high meat yield. Background Art

[0002] The seed industry is the core of agriculture, a strategic and fundamental industry, and a key material foundation for the high-quality development of the fishery industry. The Pacific oyster (Crassostrea gigas), also known as the Pacific oyster, is Shandong Province's largest commercial shellfish. In 2022, my country's total oyster production reached 6.2 million tons. In comparison, due to the varying quality and appearance of farmed oysters in my country, such as quality and shell shape, the price of domestically produced oysters is only one-tenth of that of imported oysters, or even lower.

[0003] What shape of oysters are popular? From the perspective of breeding and consumption, ideal oysters are considered to be wide and thick, that is, the shell shape is "palm-shaped". On the contrary, slender oysters such as "shoe sole-shaped" or "banana-shaped" are considered to be unpopular in the market, and there is also a significant difference in the meat yield of the two shell-shaped long oysters. At present, there are 7 new varieties of long oysters approved by the National Original Breeding Committee, among which the long oyster "Haida No. 1" (GS-01-005-2013) is the first new oyster variety cultivated in my country, filling the gap in the cultivation of oyster varieties in my country. The new variety has the characteristics of fast growth rate and regular shell shape; the long oyster "Haida No. 2" (GS-01-007-2016) uses golden shell color and growth rate as the target traits for breeding, and the left and right shells and mantle are both bright golden yellow; the long oyster "Haida No. 3" (GS-01-007-2018) uses black shell and growth rate as the target traits, and the left and right shells are and mantle are both black; the long oyster "Luyi No. 1" (GS-01-006-2020) and the long oyster "Haili No. 1" (GS-01-007-2020) both use glycogen content as the target trait, which significantly improves the meat quality of the long oyster; the long oyster "Haida No. 4" (GS-02-008-2022) is a new variety of long oyster bred by hybridization between the long oyster matching lines, and its parents both use shell height as the target trait; the long oyster "Frontier No. 1" (GS-02-009-2022) is a triploid long oyster bred by interploidy hybridization, and its tetraploid father and diploid mother both use shell height as the breeding target.

[0004] So far, there is no new long oyster variety bred with shell length and meat yield as the selection targets. Summary of the Invention

[0005] In order to solve the above technical problems, the present invention provides a method for breeding a new strain of palm-shaped oysters with high meat yield, comprising the following steps:

[0006] (1) Conduct population genetic analysis on Crassostrea gigas from different geographical origins to determine the genetic distance between populations;

[0007] (2) Homogenize the culture of long oysters to obtain the coefficient of variation of shell length and meat yield of long oysters;

[0008] (3) Calculating the genetic parameters of Crassostrea gigas, including the heritability of adult shell length and meat yield, and the genetic correlation between the two indicators;

[0009] (4) Based on the genetic parameters of shell length and meat yield of long oysters, the family breeding values ​​of the two traits were calculated, the weight values ​​of shell length and meat yield were set respectively, the comprehensive breeding value was calculated, and the optimal family was selected according to the proportion;

[0010] (5) Based on the genetic distance results of each geographical population, inter-population family pairing is performed to improve the genetic diversity of the selected offspring;

[0011] (6) A combination of family selection and group selection is adopted, with shell length and meat yield as the breeding targets. Seed oysters are retained in each generation according to the set seed retention rate. The number of male and female seed oysters is maintained above the set number respectively, and the breeding group maintains a matching system.

[0012] Furthermore, the calculation of the heritability of the shell length and meat yield of adult long oysters, as well as the genetic correlation between shell length and meat yield in step (3) refers to constructing a family using the partial factor method, cultivating individual oysters, and then measuring phenotypic data.

[0013] Furthermore, step (4) of setting weights for shell length and meat yield, calculating the comprehensive breeding value, and screening the optimal families in proportion refers to setting the weights for shell length and meat yield to approximately 70% and 30%, respectively, calculating the comprehensive breeding value, and screening the top 3%-10% of the optimal families.

[0014] Furthermore, the step (6) described in the method of combining family selection with group selection, with shell length and meat yield as the breeding targets, retains breeding clams according to the set seed retention rate in each generation, and the number of male and female breeding clams is kept above the set number, which means that breeding clams are retained according to the seed retention rate of 3%-10% in each generation, and the number of male and female breeding clams is kept above 60 respectively.

[0015] Furthermore, the breeding population in step (6) retains supporting lines, which means that in order to prevent the phenomenon of inbreeding depression after multiple generations of breeding, the new variety retains more than two parallel breeding supporting lines, and there is no blood relationship between the breeding supporting lines.

[0016] The beneficial effects of the present invention are as follows: through the selection of the shell length index of long oysters, the shell length is significantly lengthened, which is more than 17.22% higher than that of the control group; the shell length / shell height is more than 26.22% higher than that of the control group, and the shell shape is "palm-shaped"; through the selection of the meat yield, the meat yield is more than 10.66% higher than that of the unselected control group, and the genetic stability of each index is good (Table 1); due to the high positive genetic correlation between multiple traits, the wet weight, adductor muscle tension and soft body weight of the selected new strain are all improved; and due to the increase in adductor muscle tension, the breeding survival rate of the selected new strain is high, and the opening rate of commercial oysters is low during sales and transportation, and the preservation effect is good; at the same time, the new long oyster strain has high market recognition and the sales price is more than 50% higher than that of ordinary oysters. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The method for breeding the new palm-shaped and high-meat-yield oyster strain of the present invention is shown in FIG. DETAILED DESCRIPTION

[0018] 1. Collect long oyster populations and analyze genetic diversity and population differentiation

[0019] In 2013, four populations of Crassostrea gigas were collected from Kongtong Island (KTD), Yantai, Shandong; Huangdao (HD), Qingdao; Wendeng (WD), Weihai; and Zhuanghe (ZH), Dalian, Liaoning, by natural seed collection in aquaculture areas. These populations were grown out in 2014, and genetic diversity was analyzed using 21 highly polymorphic microsatellite primers (Table 2). The polymorphic information content (PIC) values ​​were >0.856, all above 0.5, indicating high genetic diversity. Population differentiation analysis revealed genetic differentiation coefficients (Fst) values ​​>0.015, all above 0.015, indicating that all four populations exhibited moderate or above genetic differentiation (Tables 3 and 4).

[0020] Table 2: Basic information of 21 pairs of long oyster microsatellite primers

[0021]

[0022]

[0023]

[0024] Table 3: Genetic diversity of four populations of Crassostrea gigas

[0025]

[0026] Table 4: Differentiation index Fst (lower left) and gene flow Nm (upper right) among four long oyster populations

[0027]

[0028] 2. Constructing the basic population (P), homogenization breeding, phenotypic trait analysis, and genetic parameter analysis

[0029] In 2014, 300 individuals were randomly selected from each of the four populations and established through dissection and fertilization. These individuals were then placed in the same waters (around Kongtong Island) for a year of homogenous breeding. Phenotypic analysis of the four populations revealed significant differences in shell length (51.13±6.57 mm) and meat yield (16.63±2.86%). The coefficients of variation (the ratio of the standard deviation to the mean) for these two parameters were 0.1285 and 0.1718, respectively, indicating ample room for further breeding. The genetic parameters of shell length and meat yield of long oysters cultured in the waters of Kongtong Island were evaluated. Using ASReml software, the heritability of shell length and meat yield of long oysters was calculated to be 0.65±0.14 and 0.35±0.12, respectively, which were medium to high heritabilities; the genetic correlation between shell length and meat yield of long oysters was 0.48±0.24, which was a positive genetic correlation.

[0030] 3. First generation family breeding

[0031] Based on the results of genetic differentiation (Table 4), the two most genetically differentiated populations were the KTD and WD populations, and the HD and ZH populations. During the mature stage of gonadal development, breeding families were constructed from each of the four populations: KTD, HD, WD, and ZH. In 2015, 80 families were constructed from the one-year-old KTD and WD populations, with a seed retention rate of 10% (20% for shell length and 50% for meat yield). In 2016, 75 families were constructed from the two-year-old HD and ZH populations, with a seed retention rate of 10% (20% for shell length and 50% for meat yield).

[0032] 4. Use group breeding technology to breed new varieties with rapid shell growth and high meat yield in the 2nd to 4th generations

[0033] In 2017, the second generation of population selection was conducted using the breeding data management platform. Using the breeding data management and analysis cloud platform developed by the project team, the family breeding values ​​of each population family constructed in 2015 and 2016 were analyzed. Weights for each trait were assigned (shell length was weighted at 71.4% and meat yield was weighted at 28.6%), and comprehensive breeding values ​​were calculated. Candidate parent families were then selected based on the rankings. Within-family selection was then used to identify candidate parents, resulting in a final seed retention rate of 4%. Inter-population matings were conducted between the KTD and WD populations constructed in 2015 to establish a breeding pair (LY-4). Inter-population matings were conducted between the HD and ZH populations constructed in 2016 to establish a breeding pair (LY-7). The number of male and female scallops was controlled to be above 60 to maintain genetic diversity.

[0034] In 2018 and 2019, the third and fourth generation groups of two breeding matching groups LY-4 and LY-7 were selected respectively, with a seed retention rate of 5% (among which the seed retention rate of shell length index was 10%, and the seed retention rate of meat yield index was 50%), and the number of male and female breeding clams was controlled at 50-60 respectively to maintain genetic diversity.

[0035] 5. Comparative experiment of pilot breeding for two consecutive years

[0036] In 2020 and 2021, two selected breeding lines, LY-4 and LY-7, were respectively used for pilot propagation and breeding, with a total aquaculture area of ​​over 1,200 mu in Yantai, Weihai, and Rizhao, Shandong Province, and Dalian, Liaoning Province. The new long oyster strain under review has stable shell length and meat yield traits, a wide, palm-shaped shell (shell length / shell height ratio > 0.60), and a meat yield that is more than 10.66% higher than that of the control group. Due to the high positive genetic correlation between multiple traits, the wet weight, adductor muscle tension, and soft body weight of the new strain have all been improved. Moreover, due to the increased adductor muscle tension, the new strain has a high survival rate, and the commercial oysters have a low opening rate and good freshness preservation during sales and transportation. This new strain has high market recognition, a high market price, and broad market prospects.

[0037] Through selective breeding for shell length, the shell length of long oysters increased significantly, by more than 17.22% compared with the control group; the shell length / shell height ratio increased by more than 26.22% compared with the control group, and the shell shape became "palm-shaped"; through selective breeding for meat yield, the meat yield increased by more than 10.66% compared with the unselected control group, and the genetic stability of each indicator was good (Table 1).

[0038] Table 1 Comparison of breeding effects.

[0039]

Claims

1. A method for breeding a new strain of palm-shaped oysters with high meat yield, comprising the following steps: (1) Conduct population genetic analysis on Crassostrea gigas from different geographical origins to determine the genetic distance between populations; (2) Homogenize the culture of long oysters to obtain the coefficient of variation of shell length and meat yield of long oysters; (3) Calculating the genetic parameters of Crassostrea gigas, including the heritability of adult shell length and meat yield, as well as the genetic correlation between the two parameters; (4) Based on the genetic parameters of shell length and meat yield of long oysters, the family breeding values ​​of the two traits were calculated, the weight values ​​of shell length and meat yield were set respectively, the comprehensive breeding value was calculated, and the optimal family was selected according to the proportion; (5) Based on the genetic distance results of each geographical group, inter-group family pairing is carried out to improve the genetic diversity of the selected offspring; (6) A combination of family selection and group selection is adopted, with shell length and meat yield as the breeding targets. Seedlings are retained at a set seed retention rate in each generation, and the number of male and female seedlings is maintained above the set number. Seedlings are retained at a seed retention rate of 3%-10% in each generation, and the number of male and female seedlings is maintained at more than 60, respectively. The breeding group maintains a matching line. In order to prevent inbreeding depression after multiple generations of breeding, the new strain maintains more than two parallel breeding matching lines, and there is no blood relationship between the breeding matching lines. The step (4) of setting weights for shell length and meat yield, calculating the comprehensive breeding value, and selecting the optimal families in proportion refers to setting the weights for shell length and meat yield to 70% and 30% respectively, calculating the comprehensive breeding value, and selecting the top 3%-10% optimal families.

2. The method for breeding a new strain of palm-shaped oysters with high meat yield according to claim 1, characterized in that: The calculation of the heritability of the shell length and meat yield of adult long oysters, as well as the genetic correlation between shell length and meat yield in step (3) refers to constructing a family using the partial factor method, cultivating individual oysters, and then measuring phenotypic data.

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