Method for constructing specialized line of fast-growing trait of litopenaeus vannamei

Abstract

The application discloses a method for constructing a fast-growing specialized line of Litopenaeus vannamei. The method comprises the following steps: collecting and cultivating a fast-growing population, screening the fast-growing population, screening individuals in the fast-growing population for three rounds, cultivating zero-generation parents and breeding F1 generation, cultivating the F1 generation and breeding F2 generation, cultivating the F2 generation and breeding F3 generation, and dynamically maintaining the fast-growing specialized line. The shrimp line cultivation method of the application does not need to construct a family line, and has the characteristics of simplicity, high efficiency and low cost, thereby laying a technical foundation for large-scale and extensive breeding of the fast-growing trait of Litopenaeus vannamei.

Description

Technical Field

[0001] This invention belongs to the field of aquaculture technology, specifically relating to a method for constructing a specialized strain of Litopenaeus vannamei with a fast growth trait. Background Technology

[0002] Litopenaeus vannamei, also known as the whiteleg shrimp, is the most farmed shrimp species in my country and the world, and has become an important representative of high-quality protein sources for Chinese consumers. Litopenaeus vannamei farming holds a very important position in my country's aquaculture industry, and it is of great significance in promoting employment. Seed industry is the "chip" of agriculture, and the Litopenaeus vannamei seed industry is crucial to supporting the sustainable development of the entire shrimp farming industry. However, overall, my country's Litopenaeus vannamei seed industry suffers from insufficient technological innovation and weak new variety research and development capabilities. Therefore, the Litopenaeus vannamei seed industry has become one of the bottleneck problems that urgently need to be solved in my country's agricultural sector.

[0003] Currently, my country has 15 new varieties of Litopenaeus vannamei, but these varieties are mainly obtained through family pedigree construction, which requires building a large number of families generation by generation. The construction of shrimp families, the selection of offspring families, and mating require significant manpower and space in aquaculture facilities, resulting in high costs for breeding new shrimp varieties and limiting the enthusiasm of enterprises to participate in the breeding of new shrimp varieties. Furthermore, to avoid inbreeding, family propagation generally uses mating between different families, which on the one hand leads to increasingly complex pedigrees in offspring, and on the other hand may cause the loss of homozygous traits and genotypes. Therefore, it is necessary to explore low-cost and efficient methods for breeding new Litopenaeus vannamei varieties.

[0004] In the production of commercial pigs and other livestock, specialized strains with prominent traits are usually selected and bred, and then combined with strict combining ability tests are conducted to form special hybrid combinations to produce high-quality commercial pigs. This allows the commercial pigs to combine the advantages of each strain and have more obvious hybrid vigor. Shrimp are lower invertebrates and have characteristics that are significantly different from those of livestock in terms of reproductive biology. Specifically, (1) breeding shrimp can only produce for one breeding season, while excellent breeding stock of livestock such as pigs can produce for many consecutive years; (2) shrimp population reproduction follows an R strategy, where a single adult can produce millions of offspring, but only a few offspring have the opportunity to reproduce in the natural environment. In contrast, the reproduction of higher animal populations such as livestock follows a K strategy, where a single adult can only produce a few high-quality offspring, maintaining population reproduction with a low mortality rate. These two characteristics determine that the specialized strain breeding methods used for livestock such as pigs are not suitable for specialized strain breeding of shrimp. Therefore, it is necessary to develop unique specialized strain breeding methods based on the biological characteristics and breeding trait requirements of shrimp. Summary of the Invention

[0005] The purpose of this invention is to provide a method for constructing dynamic specialized strains of Litopenaeus vannamei with the characteristics of simplicity, efficiency and low cost without the need for family construction, thus laying a technical foundation for large-scale and widespread breeding of shrimp with the trait of fast growth.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A method for constructing specialized strains of Litopenaeus vannamei with the fast growth trait includes the following steps:

[0008] (1) Collection and cultivation of fast-growing populations: Collect 10,000 to 20,000 shrimp larvae from 40 to 60 different sources of fast-growing populations of Litopenaeus vannamei (P6 to P10) and cultivate them for 30 days in the same size preservation pond in the preservation workshop.

[0009] (2) Screening of fast-growing groups: 100 tails are randomly selected from the above 40-60 groups and weighed. The average weight is used to represent the growth rate of the group. The 40-60 groups are sorted according to their growth rate. The top 20-30 fast-growing groups are selected, and the rest are eliminated.

[0010] (3) First round of screening of individuals in the fast-growing population: From the 20 to 30 fast-growing populations retained above, select the 400 largest shrimp from each population and continue to cultivate them in the breeding pond;

[0011] (4) Second round of screening of individuals in the fast-growing group: After the above fast-growing group of shrimp is cultured for 60 days, a second round of screening is carried out. 200 shrimp with the largest weight and healthiest appearance are selected from each group and continue to be cultured in the breeding tank.

[0012] (5) Third round of screening of individuals in the fast-growing group: After the above fast-growing group of shrimp is cultured for 90 days, a third round of screening is carried out. 100 shrimp with the largest weight and the best appearance are selected from each group, and a total of 2,000 to 3,000 shrimp are mixed as the base group and continued to be cultured in the parent culture pond.

[0013] (6) Zero-generation parent stock cultivation and F1 generation breeding: After the above 2000-3000 fast-growing prawns are cultivated to 10-12 months of age, the males and females are separated and raised in parent stock ponds at a density of 400-600 prawns / pond. The parent stock is then subjected to routine broodstock maturation and management. Mature female prawns are promptly removed and placed in male prawn ponds for natural mating. After mating, the female prawns are removed and placed in spawning tanks for routine spawning and hatching. The offspring of all female prawns from the same batch are collected in the same nursery pond for routine prawn breeding to produce F1 generation closed-group prawn larvae with fast-growing traits.

[0014] (7) F1 generation cultivation and F2 generation breeding: Take 16,000 to 24,000 shrimp F1 generation closed population seedlings with fast growth traits (P6 to P10), continue to cultivate for 30 days, filter and select 8,000 to 12,000 shrimp individuals retained by the screen; continue to cultivate for 60 days, select 4,000 to 6,000 large and healthy individuals; continue to cultivate for 90 days, select 2,000 to 3,000 large and healthy individuals, carry out F1 generation parent cultivation according to the method in step (6) above, and carry out F2 generation breeding according to the method in step (6) above.

[0015] (8) F2 generation cultivation and F3 generation breeding: Take 16,000 to 24,000 shrimp larvae (P6 to P10) from the closed population of F2 generation with fast growth traits, continue to cultivate for 30 days, filter and select 8,000 to 12,000 shrimp individuals retained by the screen; continue to cultivate for 60 days, select 4,000 to 6,000 individuals with large size and healthy appearance; continue to cultivate for 90 days, select 2,000 to 3,000 individuals with large size and healthy appearance, carry out F2 generation parent cultivation according to the method in step (6) above, and carry out F3 generation breeding according to the method in step (6) above. The F3 generation is the obtained specialized strain of Litopenaeus vannamei with fast growth traits.

[0016] (9) Dynamic maintenance of specialized strains with fast growth traits: Starting from the F3 generation, 8 to 12 populations of fast-growing shrimp from different sources are reconstructed according to the methods in steps (1) to (5) above. 25 fast-growing shrimp individuals are taken from each population, totaling 200 to 300 individuals. These individuals are then raised to parent stock and added to the specialized strains containing 1,800 to 2,700 parent shrimp individuals. Conventional breeding operations are then carried out. After that, this step is repeated once every two generations to complete the dynamic maintenance of specialized strains with fast growth traits.

[0017] In step (5), the weight of the basic group of shrimp is ≥15g.

[0018] In step (6), the weight of the fast-growing shrimp when separating males and females is ≥40g.

[0019] In steps (7) and (8), the aperture of the screen is 8 mm.

[0020] This invention also provides the application of the above-described construction method in the breeding of Litopenaeus vannamei. The breeding involves constructing specialized Litopenaeus vannamei strains with rapid growth traits.

[0021] Compared with traditional family construction methods, the method for constructing specialized shrimp strains with the rapid growth trait of this invention has the following advantages and positive effects:

[0022] (1) The process of constructing a specialized shrimp strain with the fast growth trait of the present invention does not require any family construction operation, which greatly reduces the labor intensity and saves a lot of manpower and space for breeding facilities. Therefore, it makes shrimp breeding work simple and easy, and lays a technical foundation for the large-scale and widespread breeding of shrimp with the fast growth trait.

[0023] (2) In the past, in order to avoid inbreeding, it was necessary to establish families from different sources and carry out complicated inter-family mating operations and pedigree records. In this invention, since individuals with fast growth traits that have been strictly selected from 20 to 30 shrimp populations from different sources are mixed in equal proportions, theoretically the maximum probability of inbreeding is only 1.25 to 2.5%. Even if there are undesirable offspring from inbreeding, they will be eliminated in the three rounds of selection of individuals in the fast-growing population due to their trait disadvantage.

[0024] (3) Due to cost and facility space limitations, the number of parental individuals in each generation of a family is very limited, which leads to a decrease in the genetic diversity of offspring. In contrast, the parental sources in each generation of this invention are very extensive, and while the traits are gradually purified and the genotypes associated with the traits are gradually homozygous, a high level of genetic diversity is maintained.

[0025] (4) Starting from the F3 generation, every two generations, a new population with the fast growth trait is reintroduced to maintain the specialization of the strains in a relatively open and dynamic manner, thereby increasing genetic diversity and reducing the occurrence of genetic degradation. Attached Figure Description

[0026] Figure 1 This is a technical route for constructing specialized strains of Litopenaeus vannamei with rapid growth traits. Detailed Implementation

[0027] The following embodiments are further illustrations of the present invention, but not limitations thereof.

[0028] Example 1

[0029] From 2020 to 2024, the construction and dynamic maintenance of the fast-growing trait-specific strain FG-1 of Litopenaeus vannamei will be carried out in the following manner.

[0030] (1) Collection and cultivation of fast-growing groups: In May 2020, 15,000 shrimp larvae from 50 different sources were collected (P8) and cultivated in the same size breeding pond in the breeding workshop for 30 days.

[0031] (2) Screening of fast-growing groups: 100 tails were randomly selected from the above 50 groups and weighed. The average weight was used to represent the growth rate of the group. The 50 groups were sorted according to their growth rate. The top 25 fast-growing groups were retained, and the rest were eliminated.

[0032] (3) First round of screening of individuals in the fast-growing population: 400 of the largest shrimp from each of the 25 fast-growing populations were selected and continued to be cultivated in the breeding pond.

[0033] (4) Second round of screening of individuals in the fast-growing group: After the above fast-growing group of shrimp is cultured for 60 days, a second round of screening is carried out. 200 shrimp with the largest weight and the best appearance are selected from each group and continue to be cultured in the breeding tank.

[0034] (5) Third round of screening of individuals in the fast-growing group: After the above fast-growing group of shrimp is cultured for 90 days, a third round of screening is carried out. 100 shrimp with the largest weight and healthy appearance are selected from each group, and a total of 2,500 shrimp (weight ≥15g) are mixed as the base group (generation zero) and continued to be cultured in the parent culture pond.

[0035] (6) Zero-generation broodstock rearing and F1 generation breeding: After the above 2,500 fast-growing shrimp were raised to 11 months of age (weight ≥40g), males and females were separated and cultured in separate broodstock ponds at a rate of 500 shrimp / pond, and routine broodstock maturation and management were carried out. In April 2021, mature female shrimp were promptly removed and placed in male shrimp ponds for natural mating. After mating, the female shrimp were removed and placed in spawning tanks for routine spawning and hatching operations. The offspring of all female shrimp from the same batch of spawning were collected in the same nursery pond for routine shrimp larvae rearing operations, producing F1 generation closed-group shrimp larvae with fast-growing traits.

[0036] (7) F1 generation rearing and F2 generation breeding: In May 2021, 20,000 shrimp F1 generation closed population seedlings with fast growth traits were taken (P8); after 30 days of rearing, the shrimp were filtered and screened using a sieve with an 8mm aperture, retaining 10,000 shrimp individuals trapped by the sieve. After 60 days of rearing, 5,000 large and healthy individuals were selected; after 90 days of rearing, 2,500 large and healthy individuals were selected and F1 generation parent stock were reared according to the method in step (6) above. In April 2022, F2 generation breeding was carried out according to the method in step (6) above.

[0037] (8) F2 generation cultivation and F3 generation breeding: In May 2022, 20,000 F2 generation closed population shrimp larvae with fast growth traits were taken (P8); after 30 days of cultivation, 10,000 shrimp individuals were retained by filtration using an 8mm mesh screen; after 60 days of cultivation, 5,000 large and healthy individuals were selected; after 90 days of cultivation, 2,500 large and healthy individuals were selected and F2 generation parent stock were cultivated according to the method in step (6) above. In April 2023, F3 generation breeding was carried out according to the breeding method in step (6) above, and the F3 generation was the FG-1 specialized strain of Litopenaeus vannamei with fast growth traits.

[0038] (9) Dynamic maintenance of the fast-growing trait specialized strain: In May 2023, starting from the F3 generation, 10 fast-growing shrimp populations with different sources were reconstructed according to the methods in steps (1) to (5) above. 25 fast-growing shrimp individuals were taken from each population (a total of 250 individuals) and bred to parent stock. In April 2024, these individuals were added to the above-mentioned specialized strain FG-1, which contains 2250 parent shrimp, and then routine breeding operations were carried out to complete the dynamic maintenance of the fast-growing trait specialized strain FG-1.

[0039] Example 2

[0040] From 2021 to 2024, the FG-2 strain, a specialized line for the fast growth trait of Litopenaeus vannamei, was constructed using the following method.

[0041] (1) Collection and cultivation of fast-growing groups: In May 2021, 20,000 shrimp larvae from 60 different sources were collected and cultivated for 30 days in the same size preservation pond in the preservation workshop.

[0042] (2) Screening of fast-growing groups: 100 tails were randomly selected from the above 60 groups and weighed. The average weight was used to represent the growth rate. The 60 groups were sorted according to their growth rate. The top 30 fast-growing groups were retained, and the rest were eliminated.

[0043] (3) First round of screening of individuals in the fast-growing population: 400 of the largest shrimp from each of the 30 fast-growing populations were selected and continued to be cultivated in the breeding pond.

[0044] (4) Second round of screening of individuals in the fast-growing group: After the above fast-growing group of shrimp is cultured for 60 days, a second round of screening is carried out. 200 shrimp with the largest weight and the best appearance are selected from each group and continue to be cultured in the breeding tank.

[0045] (5) Third round of screening of individuals in the fast-growing group: After the above fast-growing group of shrimp is cultured for 90 days, a third round of screening is carried out. 100 shrimp with the largest weight and healthiest appearance (weight ≥15g) are selected from each group, and a total of 3,000 shrimp are mixed as the base group (generation zero) and continued to be cultured in the parent culture pond.

[0046] (6) Generation 0 broodstock rearing and F1 generation breeding: After the above 3000 fast-growing shrimp were reared to 11 months of age (weight ≥40g), males and females were separated and cultured in separate broodstock ponds at a rate of 500 shrimp / pond, and routine broodstock maturation and management were carried out. In April 2022, mature female shrimp were promptly removed and placed in male shrimp ponds for natural mating. After mating, the female shrimp were removed and placed in spawning tanks for routine spawning and hatching operations. The offspring of all female shrimp from the same batch of spawning were collected in the same nursery pond for routine shrimp larvae rearing operations, producing F1 generation closed-group shrimp larvae with fast-growing traits.

[0047] (7) F1 generation rearing and F2 generation breeding: In May 2022, 24,000 shrimp F1 generation closed population seedlings with fast growth traits (P10) were taken; after 30 days of rearing, the shrimp were filtered and screened using a sieve with an 8mm aperture, retaining 12,000 shrimp individuals trapped by the sieve. After 60 days of rearing, 6,000 large and healthy individuals were selected; after 90 days of rearing, 3,000 large and healthy individuals were selected and F1 generation parent stock were reared according to the method in step (6) above. In April 2023, F2 generation breeding was carried out according to the method in step (6) above.

[0048] (8) F2 generation cultivation and F3 generation breeding: In May 2023, 24,000 shrimp larvae (P10) from the closed F2 generation population with the fast growth trait were taken; after 30 days of cultivation, the shrimp were filtered and screened using a sieve with an 8mm aperture, retaining 12,000 shrimp individuals trapped by the sieve; after 60 days of cultivation, 6,000 large and healthy individuals were selected; after 90 days of cultivation, 3,000 large and healthy individuals were selected, and F2 generation parent stock cultivation was carried out according to the method in step (6) above. In April 2024, F3 generation breeding was carried out according to the breeding method in step (6) above, and the F3 generation was the FG-2 specialized strain of Litopenaeus vannamei with the fast growth trait.

[0049] Example 3

[0050] Comparison of growth traits between the fast-growing Litopenaeus vannamei specialized strain FG-2 and the common strain.

[0051] In May 2024, the growth rate of the fast-growing specialized strain FG-2 was compared with that of commercially purchased HQ fast-growing shrimp larvae. Two hundred shrimp larvae from each strain (both 0.8-1 cm in body length) were collected and cultured in tanks containing 600 L of seawater for 60 days, under normal culture management. After 60 days, 50 shrimp from each strain were randomly selected for weight measurement. The results are shown in Table 1.

[0052] Table 1. Comparison of growth rates between the fast-growing specialized strain FG-2 and the conventional fast-growing HQ variety (60 days, n=50)

[0053]

[0054] As shown in Table 1, after 60 days of cultivation, the average weight of the fast-growing specialized strain FG-2 reached 11.0g, and the average daily weight gain reached 183.3mg / d. Its growth rate was 11.1% higher than that of the control strain HQ, demonstrating the growth rate advantage of the fast-growing specialized strain FG-2.

[0055] The above are merely preferred embodiments of the present invention. It should be noted that the above preferred embodiments should not be considered as limitations on the present invention, and the scope of protection of the present invention should be determined by the scope defined in the claims. For those skilled in the art, several improvements and modifications can be made without departing from the spirit and scope of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for constructing a specialized strain of Litopenaeus vannamei with the trait of rapid growth, characterized in that, Includes the following steps: (1) Collection and cultivation of fast-growing groups: Collect 10,000 to 20,000 shrimp larvae from 40 to 60 different sources of fast-growing groups of Litopenaeus vannamei and cultivate them for 30 days in the same size preservation pond in the preservation workshop. (2) Screening of fast-growing groups: 100 tails are randomly selected from the above 40-60 groups and weighed. The average weight is used to represent the growth rate of the group. The 40-60 groups are sorted according to their growth rate. The top 20-30 fast-growing groups are selected, and the rest are eliminated. (3) First round of screening of individuals in the fast-growing population: From the 20 to 30 fast-growing populations retained above, select the 400 largest shrimp from each population and continue to cultivate them in the breeding pond; (4) Second round of screening of individuals in the fast-growing group: After the above fast-growing group of shrimp is cultured for 60 days, a second round of screening is carried out. 200 shrimp with the largest weight and healthiest appearance are selected from each group and continue to be cultured in the breeding tank. (5) Third round of screening of individuals in the fast-growing group: After the above fast-growing group of shrimp is cultured for 90 days, a third round of screening is carried out. 100 shrimp with the largest weight and the best appearance are selected from each group, and a total of 2,000 to 3,000 shrimp are mixed as the base group and continued to be cultured in the parent culture pond. (6) Zero-generation parent stock cultivation and F1 generation breeding: After the above 2000-3000 fast-growing prawns are cultivated to 10-12 months of age, the males and females are separated and raised in parent stock ponds at a density of 400-600 prawns / pond. The parent stock is then subjected to routine broodstock maturation and management. Mature female prawns are promptly removed and placed in male prawn ponds for natural mating. After mating, the female prawns are removed and placed in spawning tanks for routine spawning and hatching. The offspring of all female prawns from the same batch are collected in the same nursery pond for routine prawn breeding to produce F1 generation closed-group prawn larvae with fast-growing traits. (7) F1 generation cultivation and F2 generation breeding: Take 16,000 to 24,000 shrimp F1 generation closed population seedlings with fast growth traits, continue to cultivate for 30 days, filter and select 8,000 to 12,000 shrimp individuals retained by the screen; continue to cultivate for 60 days, select 4,000 to 6,000 large and healthy individuals; continue to cultivate for 90 days, select 2,000 to 3,000 large and healthy individuals, carry out F1 generation parent cultivation according to the method in step (6) above, and carry out F2 generation breeding according to the method in step (6) above. (8) F2 generation cultivation and F3 generation breeding: Take 16,000 to 24,000 shrimp larvae from the closed population of F2 generation with fast growth traits, continue to cultivate for 30 days, filter and select 8,000 to 12,000 shrimp individuals retained by the screen; continue to cultivate for 60 days, select 4,000 to 6,000 individuals with large size and healthy appearance; continue to cultivate for 90 days, select 2,000 to 3,000 individuals with large size and healthy appearance, carry out F2 generation parent cultivation according to the method in step (6) above, and carry out F3 generation breeding according to the method in step (6) above. The F3 generation is the obtained specialized strain of Litopenaeus vannamei with fast growth traits. (9) Dynamic maintenance of specialized strains with fast growth traits: Starting from the F3 generation, 8 to 12 populations of fast-growing shrimp from different sources are reconstructed according to the methods in steps (1) to (5) above. 25 fast-growing shrimp individuals are taken from each population, totaling 200 to 300 individuals. These individuals are then raised to parent stock and added to the specialized strains containing 1,800 to 2,700 parent shrimp individuals. Conventional breeding operations are then carried out. After that, this step is repeated once every two generations to complete the dynamic maintenance of specialized strains with fast growth traits.

2. The method for constructing specialized strains of Litopenaeus vannamei with fast growth traits according to claim 1, characterized in that, In step (5), the weight of the basic group of shrimp is ≥15g.

3. The method for constructing specialized strains of Litopenaeus vannamei with fast growth traits according to claim 1, characterized in that, In step (6), the weight of the fast-growing shrimp when separating males and females is ≥40g.

4. The method for constructing specialized strains of Litopenaeus vannamei with fast growth traits according to claim 1, characterized in that, In steps (7) and (8), the aperture of the screen is 8 mm.

5. The application of the construction method according to any one of claims 1-4 in the breeding of Litopenaeus vannamei.

6. The application according to claim 5, characterized in that, The breeding program aims to develop specialized strains of Litopenaeus vannamei with rapid growth characteristics.

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