Litopenaeus vannamei nitrite-resistant character specialized strain construction method

Abstract

The invention discloses a construction method of a dynamic specialized strain with nitrite-resistant character of litopenaeus vannamei. The method comprises the following steps: collecting and cultivating a nitrite-tolerant population, screening the nitrite-tolerant population, screening individuals in the nitrite-tolerant population for three rounds, cultivating a zero-generation parent and breeding an F1 generation, cultivating the F1 generation and breeding an F2 generation, cultivating the F2 generation and breeding an F3 generation, dynamically maintaining a specialized strain with nitrite-tolerant characters, and the like. According to the prawn specialized strain breeding method, family construction is not needed, the method has the advantages of being simple, efficient and low in cost, and a technical foundation is laid for large-scale and wide breeding of the prawn nitrite resistance character.

Description

Technical Field

[0001] The invention belongs to the technical field of aquaculture, and in particular relates to a method for constructing a specialized strain of Litopenaeus vannamei with nitrite resistance traits. Background Art

[0002] Nitrite nitrogen and ammonia nitrogen are important pollutants in intensive shrimp farming environments. Currently, nitrite nitrogen has become one of the main stress factors in shrimp farming systems, especially in factory-based and small-shed farming models. Excessive and difficult-to-control nitrite nitrogen has become a prominent problem, seriously affecting the growth rate and survival rate of shrimp. Currently, there are no new shrimp varieties with nitrite resistance on the market. Therefore, it is urgent to cultivate new shrimp varieties with outstanding nitrite resistance.

[0003] At present, my country has 15 new varieties of Penaeus vannamei, but these new varieties are mainly obtained by the method of building families. In the process of breeding new varieties, a large number of families need to be built generation by generation. The construction of shrimp families, the selection of offspring families, and group mating require a lot of manpower and occupy a lot of breeding facility space, resulting in huge costs for the breeding of new shrimp varieties, which limits the enthusiasm of enterprises to participate in the breeding of new shrimp varieties. In addition, in order to avoid inbreeding, family transmission generally adopts the method of mating between different families. On the one hand, it makes the pedigree of the offspring gradually complicated. On the other hand, mating between families may also cause the loss of already homozygous traits and genotypes. Based on this, it is also necessary to explore low-cost and efficient breeding methods for new varieties of Penaeus vannamei.

[0004] In the production of commercial pigs and other livestock, it is usually necessary to breed specialized strains with outstanding traits, conduct strict compatibility tests, and form special hybrid combinations to produce high-quality commercial pigs, so that commercial pigs can concentrate the advantages of various strains and have more obvious hybrid advantages. Shrimp belongs to lower invertebrates and has obvious characteristics different from livestock in reproductive biology. Specifically, (1) 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 the 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, while livestock and other higher animal population reproduction follows the K strategy, where a single adult can only produce a few high-quality offspring and maintain population reproduction with a low mortality rate. The above two characteristics determine that the specialized strain breeding method of livestock such as pigs is not suitable for the specialized strain breeding of shrimp. Therefore, it is necessary to develop a unique specialized strain breeding method based on the biological characteristics of shrimp and the breeding trait requirements. Summary of the invention

[0005] The purpose of the present invention is to provide a method for constructing a specialized strain of nitrite-resistant Penaeus vannamei without the need for family construction, which is simple, efficient and low-cost, and lays a technical foundation for large-scale and extensive breeding of shrimp with nitrite-resistant traits.

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

[0007] A method for constructing a specialized strain of Litopenaeus vannamei with nitrite resistance traits comprises the following steps:

[0008] (1) Collection and cultivation of nitrite-resistant populations: 10,000 to 20,000 shrimp fry of Penaeus vannamei from 20 to 40 different sources, with a body length of 2 to 3 cm, were collected and placed in seed storage pools of the same specifications in the seed storage workshop;

[0009] (2) Screening of nitrite-resistant populations: 200 shrimp fry were selected from each of the above populations and placed in a test barrel with ordinary seawater for 48 hours. Sodium nitrite was added to make NO 2 -N final concentration was 100mg / L (in terms of nitrogen), and the shrimps were raised according to conventional feeding and management methods; stress resistance screening was performed for 96 hours, and the activities and feeding conditions of the shrimps in the pool were observed 4 times a day, and dead shrimps were removed in time. After 96 hours, the number of surviving shrimps was counted, and the survival rate was calculated. The 10 to 20 groups with the highest survival rate were retained, and the rest were eliminated;

[0010] (3) The first round of screening of individuals in the nitrite-tolerant population: 10,000 shrimp fry with an average body length of 2 to 3 cm were randomly selected from each population and temporarily cultured in ordinary seawater for 48 hours; sodium nitrite was added to the clean seawater in the screening pool to make NO 2 -N final concentration is 100mg / L; transfer the tested shrimp seedlings into the screening pool and start stress resistance screening; feed them according to conventional feeding and management methods; stress resistance screening lasts for 96 hours, observe the activity and feeding of the shrimps in the pool 4 times a day, remove the unresponsive, empty stomach, dead and dying shrimps in time, and the shrimps that survive after 96 hours are the shrimp breeding materials that have passed the first test;

[0011] (4) Second round of screening of individuals in the nitrite-resistant population: After 60 days of indoor cultivation, a second round of nitrite-resistant screening was conducted according to the test method in step (3) above. The stress resistance screening time was 96 hours. The feeding situation of the shrimp in the pond was observed every morning, noon and evening. The shrimps that were unresponsive, had empty intestines and stomachs, and were dead or dying were removed in time. The shrimps that remained after 96 hours were the breeding materials that passed the second screening and continued the normal cultivation process.

[0012] (5) The third round of screening of individuals in the nitrite-resistant population: After 90 days of indoor cultivation, the third round of stress resistance screening was carried out according to the test method of the above step (3); the stress resistance screening lasted for 96 hours, and the shrimp were fed normally. The feeding situation of the shrimp in the screening pool was observed every morning, noon and evening, and the shrimps with slow reaction, empty intestine and stomach, dead and dying were removed in time, and the small shrimps were removed; the shrimps remaining after 96 hours were the breeding materials that passed the third screening, and the surviving individuals of each group were temporarily raised for another 3 days. The shrimps with large size, healthy appearance and normal feeding were selected from 10 to 20 groups, totaling 2,000 to 3,000 tails, and the groups were mixed as the zero generation, and continued to be cultivated in the parent breeding pond;

[0013] (6) Cultivation of zero-generation parents and breeding of F1 generation: After the above-mentioned 2,000 to 3,000 nitrite-resistant shrimps are cultured to 10 to 12 months of age, the males and females are separated and cultured in parent ponds at a rate of 400 to 600 per pond, and conventional parent ripening operations and management are performed; mature female shrimps are promptly removed and placed in male shrimp ponds for natural mating; after mating, the female shrimps are removed and placed in spawning barrels for conventional spawning and hatching operations; all offspring of the same batch of spawning female shrimps are collected in the same nursery pond for conventional shrimp nursery operations, producing F1 generation closed group shrimp fry with fast-growing traits;

[0014] (7) F1 generation cultivation and F2 generation breeding: 16,000 to 24,000 shrimp F1 generation closed population seedlings (P6 to P10) with nitrite resistance are taken, and they are further cultivated to 2 to 3 cm, and the first round of nitrite resistance trait screening is performed according to the test method of step (3) above, and 8,000 to 12,000 surviving shrimp individuals are retained; the cultivation is continued for 60 days, and the second round of nitrite resistance trait screening is performed according to the test method of step (3) above, and 4,000 to 6,000 surviving shrimp individuals are retained; the cultivation is continued for 90 days, and the second round of nitrite resistance trait screening is performed according to the test method of step (3) above, and 2,000 to 3,000 surviving shrimp individuals are retained, and the F1 generation parent cultivation is performed according to the method in step (6) above, and the F2 generation breeding is performed according to the method in step (6) above;

[0015] (8) F2 generation cultivation and F3 generation breeding: 16,000 to 24,000 shrimp F2 generation closed population seedlings (P6 to P10) with nitrite resistance are taken, and they are further cultivated to 2 to 3 cm, and the first round of nitrite resistance trait screening is performed according to the test method of step (3) above, and 8,000 to 12,000 surviving shrimp individuals are retained; the cultivation is continued for 60 days, and the second round of nitrite resistance trait screening is performed according to the test method of step (3) above, and 4,000 to 6,000 surviving shrimp individuals are retained; the cultivation is continued for 90 days, and the second round of nitrite resistance trait screening is performed according to the test method of step (3) above, and 2,000 to 3,000 surviving shrimp individuals are retained, and the F2 generation parents are cultivated according to the method in step (6) above, and the F3 generation is bred according to the method in step (6) above, and the F3 generation is the obtained specialized strain of Penaeus vannamei with nitrite resistance trait;

[0016] (9) Dynamic maintenance of specialized strains with nitrite resistance: Starting from the F3 generation, 2 to 4 shrimp populations with nitrite resistance from different sources are reconstructed according to the methods of steps (1) to (5) above. 75 to 100 nitrite-resistant shrimp individuals are selected from each population, totaling 200 to 300 shrimp individuals. These shrimp individuals are cultured to the parent and supplemented to the specialized strains containing 1,800 to 2,700 shrimp parents. Conventional breeding operations are then performed. Thereafter, this step is repeated once every two generations to complete the dynamic maintenance of specialized strains with nitrite resistance.

[0017] In step (3), the total volume of clean seawater in the screening pool is 3m 3 .

[0018] In step (5), the weight of the zero-generation shrimp is ≥15 g.

[0019] In step (6), the weight of the shrimps when they are separated into males and females is ≥ 40 g.

[0020] The present invention also provides the application of the construction method in the breeding of Penaeus vannamei, wherein the breeding is to construct a specialized strain of Penaeus vannamei with nitrite resistance.

[0021] Compared with the traditional pedigree construction method, the method for constructing a specialized strain of shrimp with nitrite resistance of the present invention has the following advantages and positive effects:

[0022] (1) The process of constructing a specialized strain of shrimp with nitrite tolerance of the present invention does not require any pedigree construction operation, thus greatly reducing the labor intensity and saving a lot of manpower and cultivation facility space, thereby making the shrimp breeding work simple and easy, and laying a technical foundation for large-scale and extensive breeding of shrimp with fast growth traits.

[0023] (2) In the past, in order to avoid inbreeding, it was necessary to establish families from different sources and conduct complex inter-family mating operations and pedigree records. In the present invention, since 10 to 20 shrimp populations from different sources with strictly screened nitrite-resistant traits are mixed in equal proportions, theoretically the maximum probability of inbreeding is only 5 to 10%. Even if there are bad offspring from inbreeding, they will be eliminated in the three rounds of screening of breeding materials due to their inferior traits.

[0024] (3) In conventional breeding methods centered on family selection, the trait performance of test shrimp is usually used to characterize the source population or family traits, thereby selecting the family, but the test shrimp itself cannot be used as breeding material. In the present invention, after undergoing a strict nitrite stress resistance test, the test shrimp individuals with good performance are directly used as breeding materials, which can truly and accurately reflect the traits of the breeding materials rather than the traits of the family to which they belong, greatly improving the accuracy of trait selection and the frequency of occurrence of trait-associated genotypes.

[0025] (4) Due to the limitation of cost and facility space, the number of source parental individuals in each generation of a family is very limited, which will lead to a decrease in the genetic diversity of the offspring. In the present invention, the source of parents in each generation is very wide, and while the traits are gradually purified and the genotypes associated with the traits are gradually homozygous, a high genetic diversity is maintained.

[0026] (5) Starting from the F3 generation, new nitrite-resistant trait groups are reintroduced every two generations to keep specialized strains relatively open and dynamically updated, increase genetic diversity, and reduce the occurrence of genetic decline. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a technical route for constructing dynamic specialized strains of Penaeus vannamei with nitrite resistance traits. DETAILED DESCRIPTION

[0028] The following examples are provided to further illustrate the present invention, rather than to limit the present invention.

[0029] Example 1

[0030] From 2020 to 2024, the construction and dynamic maintenance of the specialized strain RN-1 of Penaeus vannamei with nitrite resistance will be carried out in the following manner.

[0031] (1) Collection and cultivation of nitrite-resistant populations: In May 2020, 15,000 shrimp fry from 30 different sources, with a body length of 2 to 3 cm, were collected and placed in seed preservation pools of the same specifications in the seed preservation workshop.

[0032] (2) Screening of nitrite-resistant populations: 200 shrimp fry were selected from each of the above populations and placed in a 200-liter test barrel with ordinary seawater for 48 hours. Sodium nitrite was added to make NO 2 -N final concentration was 100 mg / L (in terms of nitrogen), and the shrimps were raised according to conventional feeding and management methods. The stress resistance screening lasted for 96 hours, and the activities and feeding conditions of the shrimps in the pool were observed 4 times a day. Dead shrimps were removed in time, and the number of surviving shrimps was counted after 96 hours, and the survival rate was calculated. The 15 groups with the highest survival rate were retained.

[0033] (3) First round of screening of individuals in the nitrite-tolerant population: In May 2020, 10,000 shrimp fry with an average body length of 2 to 3 cm were randomly selected from the 15 populations mentioned above and temporarily cultured in ordinary seawater for 48 hours. 2 The screening pool is filled with clean seawater at a depth of 30 cm, with a total volume of 3m 3 , add sodium nitrite to make NO 2 -N final concentration is 100mg / L; transfer the tested shrimp seedlings to the screening pool and start stress resistance screening; feed them according to conventional feeding and management methods. Stress resistance screening lasts for 96 hours, observe the activity and feeding of the shrimp in the pool 4 times a day, remove the unresponsive, empty stomach, dead and dying shrimp in time, and the shrimp that survive after 96 hours are the shrimp breeding materials that have passed the first test.

[0034] (4) Second round of screening of individuals in the nitrite-resistant population: After 60 days of indoor cultivation, a second round of nitrite-resistant screening was conducted according to the test method in step (3) above. The stress resistance screening time was 96 hours. The feeding situation of the shrimp in the pond was observed every morning, noon and evening, and the shrimps that were unresponsive, had empty intestines and stomachs, and were dead or dying were removed in time. The shrimps that remained after 96 hours were the breeding materials that passed the second screening and continued the normal cultivation process.

[0035] (5) The third round of screening of individuals in the nitrite-resistant group: After 90 days of indoor cultivation, the third round of stress resistance screening was carried out according to the test method of step (3) above; the stress resistance screening lasted for 96 hours, and the shrimp were fed normally. The feeding situation of the shrimp in the pond was observed every morning, noon and evening, and the shrimps with slow reaction, empty stomach, dead and dying were removed in time, and the small shrimps were removed; the shrimps that remained after 96 hours were the breeding materials that passed the third screening, and the surviving individuals in each group were temporarily raised for another 3 days. A total of 2,500 shrimps with large size, healthy appearance and normal feeding were selected from 15 groups (weight ≥ 15 g), and the groups were mixed as the zero generation, and continued to be cultivated in the parent breeding pond.

[0036] (6) Cultivation of zero-generation parents and breeding of F1 generation: After the above-mentioned 2,500 nitrite-resistant shrimps are cultivated to 11 months of age (weight ≥ 40g), the males and females are separated and 500 males / pond are cultured in parent ponds respectively, and routine parent ripening operations and management are carried out. In April 2021, mature female shrimps are promptly removed and placed in male shrimp ponds for natural mating. After mating, the female shrimps are removed and placed in spawning barrels for routine spawning and hatching operations. All offspring of the same batch of spawning female shrimps are collected in the same nursery pond for routine shrimp nursery operations to produce F1 generation closed group shrimp fry with fast-growing traits.

[0037] (7) F1 generation cultivation and F2 generation breeding: In May 2021, 20,000 F1 generation closed group shrimp seedlings with nitrite resistance traits (P8) were taken and continued to be cultivated to 2-3 cm. The first round of nitrite resistance trait screening was carried out according to the test method of step (3) above, and 10,000 surviving shrimp individuals were retained; the cultivation was continued for 60 days, and the second round of nitrite resistance trait screening was carried out according to the test method of step (3) above, and 5,000 surviving shrimp individuals were retained; the cultivation was continued for 90 days, and the second round of nitrite resistance trait screening was carried out according to the test method of step (3) above, and 2,500 surviving shrimp individuals were retained. F1 generation parent cultivation was carried out 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.

[0038] (8) F2 generation cultivation and F3 generation breeding: In May 2022, 20,000 shrimp F2 generation closed group seedlings (P8) with nitrite resistance were taken and continued to be cultivated to 2-3 cm. The first round of nitrite resistance trait screening was carried out according to the test method of step (3) above, and 10,000 surviving shrimp individuals were retained; the cultivation was continued for 60 days, and the second round of nitrite resistance trait screening was carried out according to the test method of step (3) above, and 5,000 surviving shrimp individuals were retained; the cultivation was continued for 90 days, and the second round of nitrite resistance trait screening was carried out according to the test method of step (3) above, and 2,500 surviving shrimp individuals were retained, and the F2 generation parent cultivation was carried out according to the method in step (6) above. In April 2023, the F3 generation was bred according to the method in step (6) above, and the F3 generation was the obtained specialized strain RN-1 of Penaeus vannamei with nitrite resistance trait.

[0039] (2) Dynamic maintenance of specialized strains with nitrite resistance: In May 2023, starting from the F3 generation, three shrimp populations with nitrite resistance from different sources were reconstructed according to the methods of steps (1) to (5) above. 83, 83, and 84 nitrite-resistant shrimp individuals were taken from each population (a total of 250 shrimp), cultivated to the parents, and added to the specialized strains containing 2250 shrimp parents, and then conventional breeding operations were carried out. Thereafter, this step was repeated once every two generations to complete the dynamic maintenance of specialized strains with nitrite resistance.

[0040] Example 2

[0041] From 2021 to 2024, the construction of the nitrite-resistant specialized strain RN-2 of Penaeus vannamei will be carried out in the following manner.

[0042] (1) Collection and cultivation of nitrite-resistant populations: In May 2021, 20,000 shrimp fry from 40 different sources, with a body length of 2 to 3 cm, were collected and placed in seed preservation pools of the same specifications in the seed preservation workshop.

[0043] (2) Screening of nitrite-resistant populations: 200 shrimp fry were selected from each of the above populations and placed in a 200-liter test barrel with ordinary seawater for 48 hours. Sodium nitrite was added to make NO 2 -N final concentration was 100 mg / L (in terms of nitrogen), and the shrimps were raised according to conventional feeding and management methods. The stress resistance screening lasted for 96 hours, and the activities and feeding conditions of the shrimps in the pool were observed 4 times a day. Dead shrimps were removed in time, and the number of surviving shrimps was counted after 96 hours, and the survival rate was calculated. The 20 groups with the highest survival rate were retained.

[0044] (3) First round of screening of individuals in the nitrite-tolerant population: In May 2021, 10,000 shrimp fry with an average body length of 2 to 3 cm were randomly selected from each of the above 20 populations and temporarily cultured in ordinary seawater for 48 hours. 2 The screening pool is filled with clean seawater at a depth of 30 cm, with a total volume of 3m 3 , add sodium nitrite to make NO 2 -N final concentration is 100mg / L; transfer the tested shrimp seedlings to the screening pool and start stress resistance screening; feed them according to conventional feeding and management methods. Stress resistance screening lasts for 96 hours, observe the activity and feeding of the shrimp in the pool 4 times a day, remove the unresponsive, empty stomach, dead and dying shrimp in time, and the shrimp that survive after 96 hours are the shrimp breeding materials that have passed the first test.

[0045] (4) Second round of screening of individuals in the nitrite-resistant population: After 60 days of indoor cultivation, a second round of nitrite-resistant screening was conducted according to the test method in step (3) above. The stress resistance screening time was 96 hours. The feeding situation of the shrimp in the pond was observed every morning, noon and evening, and the shrimps that were unresponsive, had empty intestines and stomachs, and were dead or dying were removed in time. The shrimps that remained after 96 hours were the breeding materials that passed the second screening and continued the normal cultivation process.

[0046] (5) The third round of screening of individuals in the nitrite-resistant group: After 90 days of indoor cultivation, the third round of stress resistance screening was carried out according to the test method of step (3) above; the stress resistance screening lasted for 96 hours, and the shrimp were fed normally. The feeding situation of the shrimp in the pond was observed every morning, noon and evening, and the shrimps with slow reaction, empty stomach, dead and dying were removed in time, and the small shrimps were removed; the shrimps that remained after 96 hours were the breeding materials that passed the third screening, and the surviving individuals in each group were temporarily raised for another 3 days. From the 20 groups, 3,000 shrimps with large size, healthy appearance and normal feeding (weight ≥ 15 g) were selected, and the groups were mixed as the zero generation, and continued to be cultivated in the parent breeding pond.

[0047] (6) Cultivation of zero-generation parents and breeding of F1 generation: After the above 3,000 nitrite-resistant shrimps are cultivated to 11 months of age (weight ≥ 40g), the males and females are separated and cultured in parent ponds at a rate of 600 per pond, and routine parent ripening operations and management are carried out. In April 2022, mature female shrimps are promptly removed and placed in male shrimp ponds for natural mating. After mating, the female shrimps are removed and placed in spawning barrels for routine spawning and hatching operations. All offspring of the same batch of spawning female shrimps are collected in the same nursery pond for routine shrimp nursery operations to produce F1 generation closed group shrimp fry with fast-growing traits.

[0048] (7) F1 generation cultivation and F2 generation breeding: In May 2022, 24,000 F1 generation closed population shrimp seedlings with nitrite resistance traits (P10) were taken and continued to be cultivated to 2-3 cm. The first round of nitrite resistance trait screening was carried out according to the test method of step (3) above, and 12,000 surviving shrimp individuals were retained; the cultivation was continued for 60 days, and the second round of nitrite resistance trait screening was carried out according to the test method of step (3) above, and 6,000 surviving shrimp individuals were retained; the cultivation was continued for 90 days, and the second round of nitrite resistance trait screening was carried out according to the test method of step (3) above, and 3,000 surviving shrimp individuals were retained. F1 generation parent cultivation was carried out 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.

[0049] (8) F2 generation cultivation and F3 generation breeding: In May 2023, 24,000 F2 generation closed population seedlings (P10) with nitrite resistance were taken and continued to be cultivated to 2-3 cm. The first round of nitrite resistance trait screening was carried out according to the test method of step (3) above, and 12,000 surviving shrimp individuals were retained; the cultivation was continued for 60 days, and the second round of nitrite resistance trait screening was carried out according to the test method of step (3) above, and 6,000 surviving shrimp individuals were retained; the cultivation was continued for 90 days, and the second round of nitrite resistance trait screening was carried out according to the test method of step (3) above, and 3,000 surviving shrimp individuals were retained, and the F2 generation parent cultivation was carried out according to the method in step (6) above. In April 2024, the F3 generation was bred according to the method in step (6) above, and the F3 generation was the obtained specialized strain RN-2 of Penaeus vannamei with nitrite resistance.

[0050] Example 3

[0051] In June 2024, 100 RN-2 seedlings of the specialized strain of Penaeus vannamei with nitrite tolerance were taken, and 100 ZD seedlings commonly available on the market were taken. The body length of the two groups of shrimp seedlings was 2-3 cm. The 100 seedlings were placed in a test bucket containing 100L of seawater, where NO 2 -N final concentration was 100mg / L, the test time was 96 hours, the activity and feeding of shrimp in the pool were observed 4 times a day, dead shrimp were removed in time, and the number of surviving shrimp was counted after 96 hours to calculate the survival rate. The results showed that the survival rate of the specialized strain RN-2 was 56%, and the survival rate of the ZD variety was 44%. The survival rate of the specialized strain RN-2 of Penaeus vannamei was 27.3% higher than that of the conventional ZD variety.

[0052] The above are only preferred embodiments of the present invention. It should be noted that the above preferred embodiments should not be regarded as limiting the present invention, and the protection scope of the present invention should be based on the scope defined by the claims. For ordinary technicians in this technical field, 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 regarded as the protection scope of the present invention.

Claims

1. A method for constructing a specialized strain of Penaeus vannamei with nitrite tolerance, characterized in that: The following steps are involved: (1) Collection and cultivation of nitrite-resistant populations: 10,000 to 20,000 shrimp fry of Penaeus vannamei from 20 to 40 different sources, with a body length of 2 to 3 cm, were collected and placed in seed storage pools of the same specifications in the seed storage workshop; (2) Screening of nitrite-resistant populations: 200 shrimp fry were selected from each of the above populations, placed in a test barrel with ordinary seawater for 48 hours, and sodium nitrite was added to make the final concentration of NO2-N 100 mg / L. The shrimps were raised according to conventional feeding and management methods; stress resistance screening was conducted for 96 hours, and the activity and feeding of the shrimps in the pond were observed 4 times a day. Dead shrimps were removed in time. After 96 hours, the number of surviving shrimps was counted and the survival rate was calculated. The 10 to 20 populations with the highest survival rate were retained, and the rest were eliminated; (3) The first round of screening of individuals in the nitrite-tolerant population: 10,000 shrimp fry were randomly selected from each population, with an average body length of 2 to 3 cm, and temporarily cultured in ordinary seawater for 48 hours; sodium nitrite was added to the clean seawater in the screening pool to make the final NO2-N concentration of 100 mg / L; the tested shrimp fry were transferred to the screening pool and stress resistance screening was started; the shrimp fry were raised according to conventional feeding and management methods; the stress resistance screening lasted for 96 hours, and the activity and feeding conditions of the shrimp in the pool were observed 4 times a day, and the unresponsive, empty-stomach, dead and dying shrimp were removed in time. The shrimp that survived after 96 hours were the shrimp breeding materials that passed the first test; (4) Second round of screening of individuals in the nitrite-resistant population: After 60 days of indoor cultivation, a second round of nitrite-resistant screening was conducted according to the test method in step (3) above. The stress resistance screening time was 96 hours. The feeding situation of the shrimp in the pond was observed every morning, noon and evening. The shrimps that were unresponsive, had empty intestines and stomachs, and were dead or dying were removed in time. The shrimps that remained after 96 hours were the breeding materials that passed the second screening and continued the normal cultivation process. (5) The third round of screening of individuals in the nitrite-resistant population: After 90 days of indoor cultivation, the third round of stress resistance screening was carried out according to the test method of the above step (3); the stress resistance screening lasted for 96 hours, and the shrimp were fed normally. The feeding situation of the shrimp in the screening pool was observed every morning, noon and evening, and the shrimps with slow reaction, empty intestine and stomach, dead and dying were removed in time, and the small shrimps were removed; the shrimps remaining after 96 hours were the breeding materials that passed the third screening, and the surviving individuals of each group were temporarily raised for another 3 days. The shrimps with large size, healthy appearance and normal feeding were selected from 10 to 20 groups, totaling 2,000 to 3,000 tails, and the groups were mixed as the zero generation, and continued to be cultivated in the parent breeding pond; (6) Cultivation of zero-generation parents and breeding of F1 generation: After the above-mentioned 2,000 to 3,000 nitrite-resistant shrimps are cultured to 10 to 12 months of age, the males and females are separated and cultured in parent ponds at a rate of 400 to 600 per pond, and conventional parent ripening operations and management are performed; mature female shrimps are promptly removed and placed in male shrimp ponds for natural mating; after mating, the female shrimps are removed and placed in spawning barrels for conventional spawning and hatching operations; all offspring of the same batch of spawning female shrimps are collected in the same nursery pond for conventional shrimp nursery operations, producing F1 generation closed group shrimp fry with fast-growing traits; (7) F1 generation cultivation and F2 generation breeding: 16,000 to 24,000 F1 generation closed population shrimp seedlings with nitrite resistance are taken, and they are further cultivated to 2 to 3 cm, and a first round of nitrite resistance trait screening is performed according to the test method of step (3) above, and 8,000 to 12,000 surviving shrimp individuals are retained; the cultivation is continued for 60 days, and a second round of nitrite resistance trait screening is performed according to the test method of step (3) above, and 4,000 to 6,000 surviving shrimp individuals are retained; the cultivation is continued for 90 days, and a second round of nitrite resistance trait screening is performed according to the test method of step (3) above, and 2,000 to 3,000 surviving shrimp individuals are retained, and F1 generation parent cultivation is performed according to the method in step (6) above, and F2 generation breeding is performed according to the method in step (6) above; (8) F2 generation cultivation and F3 generation breeding: 16,000 to 24,000 shrimp F2 generation closed population seedlings with nitrite resistance are taken, and they are further cultivated to 2 to 3 cm, and the first round of nitrite resistance trait screening is performed according to the test method of step (3) above, and 8,000 to 12,000 surviving shrimp individuals are retained; the cultivation is continued for 60 days, and the second round of nitrite resistance trait screening is performed according to the test method of step (3) above, and 4,000 to 6,000 surviving shrimp individuals are retained; the cultivation is continued for 90 days, and the second round of nitrite resistance trait screening is performed according to the test method of step (3) above, and 2,000 to 3,000 surviving shrimp individuals are retained, and the F2 generation parents are cultivated according to the method in step (6) above, and the F3 generation is bred according to the method in step (6) above, and the F3 generation is the obtained specialized strain of Penaeus vannamei with nitrite resistance trait; (9) Dynamic maintenance of specialized strains with nitrite resistance: Starting from the F3 generation, 2 to 4 shrimp populations with nitrite resistance from different sources are reconstructed according to the methods of steps (1) to (5) above. 75 to 100 nitrite-resistant shrimp individuals are selected from each population, totaling 200 to 300 shrimp individuals. These shrimp individuals are cultured to the parent and supplemented to the specialized strains containing 1,800 to 2,700 shrimp parents. Conventional breeding operations are then performed. Thereafter, this step is repeated once every two generations to complete the dynamic maintenance of specialized strains with nitrite resistance.

2. The method for constructing a specialized strain of Penaeus vannamei with nitrite tolerance according to claim 1, characterized in that: In step (3), the total volume of clean seawater in the screening pool is 3m 3 .

3. The method for constructing a specialized strain of Penaeus vannamei with nitrite tolerance according to claim 1, characterized in that: In step (5), the weight of the zero-generation shrimp is ≥15 g.

4. The method for constructing a specialized strain of Penaeus vannamei with nitrite tolerance according to claim 1, characterized in that: In step (6), the weight of the shrimps when they are separated into males and females is ≥ 40 g.

5. Application of the construction method according to any one of claims 1 to 4 in breeding of Penaeus vannamei.

6. The use according to claim 5, characterized in that: The breeding is to construct a specialized strain of Penaeus vannamei with nitrite tolerance.

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