Construction and Application of a three-line breeding system in the Peruvian scallop x Bay scallop southern subspecies hybrids

Abstract

The current invent relates to the construction and application of a three-line breeding system in the Peruvian scallopbay scallop southern subspecies hybrids. The said three-line consists of a male sterile line, a maintainer line and a restorer line. A combination of male sterile line and maintainer line is obtained by continuously backcrossing the male sterile individuals selected from F.sub.1 inter-specific hybrid families with sperm of the selfing family of the sperm-providing bay scallops until the progenies are all male sterile. The restorer line is obtained by continuously backcrossing selected individuals from the male sterile line with sperm of the selfing family of a bay scallop until the progenies are all hermaphroditic and exhibit excellent production traits. Commercial male sterile brood stocks are produced by backcrossing the male sterile line with the maintainer line and commercial hybrid spats are produced by backcrossing the male sterile line and the restorer line.

Claims

1. A three-line breeding system in the Peruvian scallopbay scallop southern subspecies hybrids. The said three-line breeding system consisting of a male sterile line, a maintainer line and a restorer line and the said Peruvian scallopbay scallop southern subspecies hybrids are progenies produced with eggs from the bay scallop southern subspecies and sperm from bay scallop southern subspecies.

2. The breeding method of the three-line breeding system in claim 1 is characterized in that: 1) Production of the male sterile individuals in the Peruvian scallopbay scallop southern subspecies hybrids and breeding of the male parents thereof: More than 20 F.sub.1 Peruvian scallopbay scallop southern subspecies hybrids families are constructed using eggs from the Peruvian scallops and sperm from the bay scallop southern subspecies. The selfing family of the sperm-providing bay scallop southern subspecies is also produced for the selection as outlined below by fertilizing its eggs with its own sperm. 2) Breeding of the male sterile line of the Peruvian scallopbay scallop southern subspecies hybrids: In the next spring, 50 individuals with excellent production traits and apparent male sterile gonad (with no obvious gonadal development in the male part of the gonad) are selected from each F.sub.1 hybrid family. Twenty bay scallop southern subspecies with excellent production traits are also selected from each selfing families of the corresponding sperm-providing bay scallop southern subspecies. Then at least 20 backcross families are constructed with the eggs from selected male sterile/female fertile individuals and sperm from selected individuals from the corresponding selfing families of the sperm-providing bay scallop southern subspecies. The sperm-providing bay scallop southern subspecies brood stocks of the backcross families are again reproduced by self-fertilization. In the following years, the male sterile/female fertile individuals from the backcross families are continuously backcrossed with individuals selected from the selfing family of the sperm-providing bay scallop southern subspecies, until all the individuals of the backcross progenies exhibit excellent traits and are male sterile and female fertile. The male sterile line of the Peruvian scallopbay scallop southern subspecies hybrids is thus obtained. 3) Breeding of the maintainer line of the Peruvian scallopbay scallop southern subspecies hybrids: The above selfing family of the sperm-providing bay scallop southern subspecies is able to render the male sterile characteristic to the progenies of the male sterile line and thus becomes the corresponding maintainer line for this male sterile line. 4) Breeding of the restorer line of the Peruvian scallopbay scallop southern subspecies hybrids: Fifty large male sterile and female fertile individuals are selected from the male sterile line and the maintainer line respectively and conditioned to ripeness. They are then induced to spawn and the eggs from the male sterile individuals are fertilized by the sperm of different bay scallop southern subspecies to establish at least 20 backcross families; meanwhile, the sperm-providing bay scallop southern subspecies are self-fertilized to establish the corresponding self-fertilization families. At harvest, the growth and survival rates of the backcross progenies are measured and the combining ability tests are carried out for each backcross family. In the following year, excellent individuals are selected from both the male sterile line and the corresponding sperm-providing bay scallop southern subspecies selfing family that correlated to the best backcross family with the highest combining ability and highest percentage of hermaphroditic individuals. After conditioning and spawning induction, eggs from the male sterile line are again backcrossed with the sperm of the selected individual from the selfing family of the sperm-providing bay scallop southern subspecies. Same selections are carried each year on the selfing family of the sperm-providing bay scallop southern subspecies until all individuals in the backcross family are hermaphroditic and exhibit excellent production traits. This selfing family of the sperm-providing bay scallop southern subspecies becomes the restorer line for the corresponding male sterile line. 5) Reproduction of the three-line breeding system: The next generation of male sterile line is produced by backcrossing the brood stocks of the male sterile line with the sperm from the corresponding maintainer line. As the scallops of the maintainer line and restorer line are hermaphroditic animals, they are reproduced by self-fertilization

3. Application of the said three-line breeding system in claim 1 in the production of commercial male sterile brood stocks of Peruvian scallop hybridsbay scallop southern subspecies: In commercial scallop hatcheries, the next generation of male sterile brood stocks are produced by fertilizing the eggs of the male sterile line with the sperm from its corresponding maintainer line at large scales and low costs.

4. Application of the said three-line breeding system in claim 1 in the production of commercial Peruvian scallopbay scallop southern subspecies hybrid spats: In commercial scallop hatcheries, the commercial Peruvian scallopbay scallop southern subspecies hybrid spats are produced by fertilizing the eggs of the male sterile brood stocks with the sperm from brood stocks of its corresponding restorer line.

5-10. (canceled)

Description

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0025] The present invention establishes a three-line breeding system, comprising of a male sterile line, a maintainer line and a restorer line of Peruvian scallopbay scallop southern subspecies hybrids and also application methods for commercial production of the Peruvian scallopbay scallop southern subspecies hybrid spats using the three-line breeding system. The specific steps arc as follows:

Embodiment 1

1) Production of the Male Sterile Individuals of the Peruvian ScallopBay Scallop Southern Subspecies Hybrids and Reproduction of the Sperm-Providing Bay Scallop Southern Subspecies:

[0026] In the first year, 50 Peruvian scallops and 50 bay scallop southern subspecies with mature gonads are selected. After air exposure for 30 min., scallops are placed in separate containers, pre-filled with 23 C. seawater for spawning induction. After spawning, the eggs and sperm of each scallop are collected separately. Eggs of a Peruvian scallop are mixed with sperm of a bay scallop southern subspecies to produce a Peruvian scallopbay scallop southern subspecies F.sub.1 hybrid family. A selfing family is produced for each sperm-providing bay scallop southern subspecies by mixing its eggs with its own sperm. In all cases, only a small amount of sperm are used to avoid adverse effect caused by excess sperm. Ideally, each egg should be surrounded by 5-6 sperm. The fertilized eggs are hatched in dark and the resulted D-larvae are collected. At least 20 F.sub.1 hybrid families and the corresponding selfing family of the sperm-providing bay scallop southern subspecies are established. Larval culture, spat nursery and adult grow-out are carried out following the routine culture methods for the Peruvian scallops.

2) Breeding of the Male Sterile Line of the Peruvian ScallopBay Scallop Southern Subspecies Hybrids:

[0027] In the next spring, at least 100 individuals with excellent production traits and apparent male sterile gonad (with no obvious gonadal development in the male part of the gonad) are selected from each F.sub.1 hybrid family. Twenty scallops with excellent production traits are also selected from each selfing families of the corresponding sperm-providing bay scallop southern subspecies. After conditioning, test spawning is carried out to determine if the individuals selected from the F.sub.1 hybrid families spawn only eggs and the eggs can be fertilized and thus to select the male sterile and yet female fertile F.sub.1 hybrid families. Then at least 50 backcross families are constructed with the eggs from selected male sterile/female fertile individuals and sperm from selected individuals from the corresponding selfing families of the sperm-providing bay scallop southern subspecies. The sperm-providing bay scallop southern subspecies brood stocks of the backcross families are again reproduced by self-fertilization. In the following years, the male sterile/female fertile individuals from the backcross families are continuously backcrossed with individuals selected from the selfing family of the sperm-providing bay scallop southern subspecies, until all the individuals of the backcross progenies exhibit excellent traits and are male sterile and female fertile. The male sterile line of the Peruvian scallopbay scallop southern subspecies hybrids is thus obtained and the selfing family of the sperm-providing bay scallop southern subspecies becomes the corresponding maintainer line for this male sterile line.

3) Breeding of the Maintainer Line of the Peruvian ScallopBay Scallop Southern Subspecies Hybrids:

[0028] Individuals with excellent production traits are selected from the maintainer line and conditioned to mature. As the scallops of the maintainer line are hermaphroditic animals, the maintainer line is reproduced by self-fertilization.

4) Breeding of the Restorer Line of the Peruvian ScallopBay Scallop Southern Subspecies Hybrids:

[0029] Fifty large male sterile and female fertile individuals are selected from the male sterile line and the maintainer line respectively and conditioned to ripeness. They are then induced to spawn and the eggs from the male sterile individuals are fertilized by the sperm of different bay scallop southern subspecies to establish at least 20 backcross families; meanwhile, the sperm-providing bay scallop southern subspecies are self-fertilized to establish the corresponding self-fertilization families. At harvest, the growth and survival rates of the backcross progenies are measured and the combining ability tests are carried out for each backcross family. In the following year, excellent individuals are selected from both the male sterile line and the corresponding sperm-providing bay scallop southern subspecies selfing family that correlated to the best backcross family with the highest combining ability and highest percentage of hermaphroditic individuals. After conditioning and spawning induction, eggs from the male sterile line are again backcrossed with the sperm of the selected individual from the selfing family of the sperm-providing bay scallop. Same selections are carried each year on the selfing family of the sperm-providing bay scallop southern subspecies until all individuals in the backcross family are hermaphroditic and exhibit excellent production traits. This selfing family of the sperm-providing bay scallop becomes the restorer line for the corresponding male sterile line. The hermaphroditic restorer line is reproduced by self-fertilization and provides sperm for the commercial production of hybrid spats.

5) Production of Commercial Peruvian ScallopBay Scallop Southern Subspecies Hybrid Spats Using the Three-Line Breeding System:

[0030] Each year, the brood stocks of the male sterile line are produced by hybridizing the male sterile line with the sperm of its maintainer line while the brood stocks of the restorer line are reproduced by self-fertilization. In commercial scallop hatcheries, the brood stocks of the male sterile line and the restorer line are selected in the ratio of 5:1 and conditioned to ripeness at the same time. Then the brood stocks of the male sterile line are induced to spawn in large tanks and the brood stocks of the restorer line are induced to spawn in 20 liter buckets. The sperm of the restorer line are collected by filtering the seawater in the buckets through a 500-mesh screen and added to the spawning tanks containing the eggs from the male sterile line brood stocks and well stirred immediately. Seawater samples are taken frequently from the tanks for observation of the fertilization under a microscope until 5-6 sperm are found around each egg. The commercial Peruvian scallop-bay scallop southern subspecies hybrid seeds can thus be produced at large scales and low costs.

Embodiment 2

[0031] In 2012, large individuals with only female part of gonads developed were selected from the F.sub.1 Peruvian scallopbay scallop southern subspecies (A. i. concentricus) hybrid family constructed in 2011 using the bay scallop southern subspecies from Zhanjing, Guangdong Province of China. After conditioning and spawning induction, two backcross families were constructed with the spawned eggs fertilized with sperm from a Bay scallop southern subspecies. At harvest in mid-November 2012, the average shell height, average shell length, average shell width and the average whole weight of the backcross families were increased by 28.5-29.7%, 28.3-29.6%, 18.5-19.1% and 91.2-93.2%, respectively. The results showed that the backcross family exhibited great production traits in growth.

[0032] After maturation in the spring of 2013, it was discovered that the progenies of the (Peruvian scallopbay scallop southern subspecies)bay scallop southern subspecies backcross families were all hermaphrodites, indicating that the restorer line of the male sterile line can be successfully bred by backcrossing the bay scallop southern subspecies with the male sterile individuals. In most progenies in another (Peruvian scallopbay scallop southern subspecies)bay scallop southern subspecies family, only the female part of their gonads developed and furthermore, the spawned eggs can be fertilized by bay scallop southern subspecies sperm, suggesting that it is possible to breed the male sterile line and the maintainer line by continuously backcrossing the Bay scallop southern subspecies with the male sterile individuals.

Embodiment 3

[0033] In 2013 and 2014, 14 F.sub.1 Peruvian scallopbay scallop southern subspecies (A. i. concentricus) hybrid families together with the selfing families of their sperm-providing bay scallop southern subspecies were established. According to the methods given in Embodiment 1, the male sterile families of the Peruvian scallop-bay scallop southern subspecies hybrids and the corresponding maintainer line and restorer line thereof can be bred and the production of commercial Peruvian scallop-bay scallop southern subspecies hybrid spats can be realized within 1-3 years.