Abstract:
The current invent relates to the construction and application of a three-line breeding system in the Peruvian scallop×bay scallop hybrids. The said three-line consists of a male sterile line, a maintainer line and a restorer line of the bay scallop×Peruvian scallop hybrids. Herein the Peruvian scallop×bay scallop hybrids are hybrids resulted from the eggs of the Peruvian scallops fertilized with sperm of the bay scallops. In constructing the three-line, male sterile individuals are selected from F 1  inter-specific hybrid families and continuously backcrossed with sperm of the selling family of the sperm-providing bay scallops of the F 1  hybrid to obtain a combination of male sterile line and maintainer line whose hybrid progenies are all male sterile. Then selected individuals from the male sterile line are continuously backcrossed with sperm from the selfing family of a bay scallop until the resulted progenies are all hermaphroditic and exhibit excellent production traits. Commercial male sterile brood stocks are produced by backcrossing the eggs of the male sterile line with the sperm of the maintainer line and commercial Peruvian scallop×bay scallop hybrid spats are produced by backcrossing the eggs of the male sterile line and sperm of the restorer line. This invent establishes the three-line breeding system in animals for the first time and efficiently overcomes the barrier of self-fertilization in the hybridization between hermaphroditic scallops. The yield of the hybrid scallops can be increased by over 50% compared with the bay scallops.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to a method for breeding commercial fingerlings of hybrid scallops, belonging to a scallop breeding technology, and in particular relates to an establishment method and an application of a bay scallop-purple scallop hybrid (the hybrid progenies of the ova of the bay scallops and the sperms of the purple scallops) three-line supporting breeding system comprising a male sterile line, a maintainer line and a restorer line. 
       BACKGROUND OF THE INVENTION 
       [0002]    The bay scallops ( Argopecten irradians ) are native to the U.S. Atlantic coast and were introduced into China in 1982. The bay scallops grow fast and are wide in temperature adaptation range and strong in stress resistance, and thus are very suitable for breeding in Northern Sea of China; at present, the yield and the breeding area of the bay scallops account for more than 50% of those of Chinese scallop breeding. However, due to long-term inbreeding after introduction, the bay scallops have heavy degradation in germplasm, which can be manifested by increasingly small specification of commercial scallops and a relatively high death rate in the breeding process; hence, the scallop breeding industry has an urgent need on genetic improvement of the bay scallops, among which hybridization breeding is one of the most effective germplasm improvement methods. 
         [0003]    To this end, the inventor introduced the purple scallops ( Argopecten purpuratus ) from Peru for the first time in 2007. The purple scallops are fast-growing medium-sized scallops native to South Pacific and belong to the Argopecten together with the bay scallops; the two types of scallops are the same in chromosome number, and both are hermaphroditic, but complementary to each other in traits such as individual size, growth and temperature adaptability. Hence, the inventor carries out interspecific hybridization on the bay scallops with the purple scallops to culture two types of hybrid first filial generations of direct cross (the ova of the purple scallops are fertilized by the sperms of the bay scallops) and reciprocal cross (the ova of the bay scallops are fertilized by the sperms of the purple scallops). The individual weight of each hybrid first filial generation is increased by about 100% in contrast with that of the bay scallops bred in the corresponding period; in the current year, the hybrid first filial generation may grow to the range of 7-8 cm, and can be continuously bred to reach a larger specification in the second year with the individual weight of more than 200 g; as a result, the two types of hybrid first filial generations are enhanced in stress resistance, and especially can live through the summer and the winter smoothly in Shandong area, whereby a tremendous industrial potential is shown (Wang, Chunde et al., 2009. Study on Interspecific Hybridization of Purple Scallops and Bay Scallops. Marine Sciences, 33(10): 84-87; Chunde Wang et al, 2011. Introduction of the Peruvian scallop and its hybridization with the bay scallop in China, Aquaculture, 2011, 310:380-387). 
         [0004]    Although the hybrid first filial generations are capable of producing great hybrid advantages, it is still highly difficult to popularize in large area, because both the purple scallops and the bay scallops are hermaphroditic scallops and discharge sperms and ova simultaneously during reproduction; the discharged ova are prone to be polluted by the sperms from the same scallops and it is difficult to obtain plenty of unfertilized ova for interspecific hybridization, leading to a great drop in the ratio of real hybridization progenies in the obtained commercial fingerlings; as a result, the increased amplitude of its yield is greatly limited. 
         [0005]    It has been discovered through study that the hermaphroditic characteristic of the two hermaphroditic scallops is similar to the monoecious characteristic of many crops. As the problem of same-flower pollination also exists in the breeding of the monoecious crops, artificial emasculation is required, and this point is similar to the self-fertilization problem encountered in the hybridization process of one bay scallop and one purple scallop. The key for agriculturally solving the problem depends on the discovery of male sterile plants; the male sterile plants are continuously backcrossed with. the male parents thereof to breed the male sterile line, the maintainer line and the restorer line, whereby a three-line supporting breeding system in crop breeding is established and large-scale production of hybrids is realized; as a result, the hybrid production problem is solved. So far, the three-line supporting breeding systems have been established in numerous crops at home and abroad and are widely applied to the hybrid production; as a result, it is a major way for greatly increasing the yield of the crops. 
         [0006]    However, in animal breeding, there has been no report on discovering male sterile and female fertile individuals so far at home and aboard, and therefore, the similar male sterile line, maintainer line and restorer liner to the crops cannot be established for hybridization breeding. Obviously, if the similar three-line supporting breeding system comprising the male sterile line, the maintainer line and the restorer line is established in animal breeding, low-cost and large-scale interspecific hybridization of hermaphroditic animals can be realized, whereby the hybridization efficiency can be improved and the stress resistance and the yield of the bred animals can be increased; as a result, a major breakthrough can be made in the animal breeding technology. 
       SUMMARY OF THE INVENTION 
       [0007]    One object of the present invention is to realize the establishment of the scallop-purple scallop hybrid three-line supporting breeding system comprising such lines as the maritime male sterile line, the maintainer line and the restorer line for the first time in animal breeding, specially in the hermaphroditic scallops, in order to overcome the defects of the existing hybrid scallop breeding technology, 
         [0008]    Another object of the present invention is to establish an application method for producing the fingerlings of the scallop-purple scallop hybrids at a large scale and a low cost by use of the three-line supporting breeding system. 
         [0009]    The three lines refer to the male sterile line, the maintainer line and the restorer line of the scallops, wherein the male sterile line is a line that is abnormal in male gonad development and thus incapable of generating functional sperms, but normal in ovum development, capable of accepting normal sperms to be fertilized and also capable of transmitting its male sterile characteristic to the progenies. It is obvious that the male sterile line is a core line of the three-line supporting system and plays a major role in providing a large number of unfertilized ova in commercial production of the hybrid fingerlings, and meanwhile, the breeding of the male sterile line depends on the maintainer line matched with the male sterile line. The male sterile line is a hybrid scallop line obtained by continuously backcrossing male sterile and ovum fertile individuals discovered accidentally with their male parents to establish backcross families until all the individuals of the backcross families are male sterile and ovum fertile. 
         [0010]    The maintainer line is also known as a male sterile line maintainer line; when the maintainer line serves as the male parent to be hybridized with the male sterile line, the first filial generation can keep the male sterile characteristic; the major function of the maintainer line is to provide sperms necessary for breeding the male sterile line. The maintainer line is a purple scallop line obtained by continuously backcrossing the purple scallops with the male sterile individuals until all the backcross progenies are male stile and ovum fertile. The maintainer line is a hermaphroditic line capable of normally breeding and capable of breeding the next-generation maintainer line through self-fertilization. 
         [0011]    The restorer line is also known as a male sterile line restorer line; after the ova of the male sterile line are fertilized by the sperms of the restorer line, the female fertility and the male fertility of the hybridization progenies generated both are restored to be normal. Hence, in animal breeding, the role of the restorer line is to provide sperms for fertilizing the ova of the male sterile line so as to realize the breeding of excellent commercial fingerlings of the hybrid scallops. The restorer line is a purple scallop line obtained by continuously backcrossing the purple scallops with the breeding scallops of the male sterile line until all the backcross progenies are hermaphroditic. The restorer line is a hermaphroditic line capable of normally breeding and capable of breeding the next-generation restorer line through self-fertilization. 
         [0012]    The present invention is based on the following ideas and practices: 1) the inventor has discovered in study that the first filial generation of the bay scallop-purple scallop hybrids (the hybridization progenies of the ova of the bay scallops and the sperms of the purple scallops) contains 2-10% of male sterile individuals that do not generate active sperms, but generate ova capable of being fertilized by the sperms of the purple scallops, and the obtained fertilized ova can develop normally so that backcrossed scallops can be obtained; 2) it has been further discovered in study that after gonadal maturation, the obtained backcrossed scallops still include about 10% of individuals that are male sterile and of which the ova can be fertilized by the sperms of the purple scallops, and therefore, as long as the ova of the male sterile individuals are continuously backcrossed with the sperms of the self-fertilization progenies of the male parent purple scallops for a plurality of generations, a male sterile line (female parent)-purple scallop (male parent) combination of which the progenies are all male sterile and ovum fertile can be bred; the purple scallop line in the combination is capable of enabling the corresponding progenies of the male sterile line to still keep the male sterile characteristic, and then the male sterile line of the bay scallop-purple scallop hybrids and the maintainer line of the male sterile line can be obtained; 3) it is further discovered in study that the maturated backcrossed scallops bred by backcrossing the sperms of the purple scallops with the ova of the male sterile individuals of the bay scallop-purple scallop hybrids still includes about 90% of hermaphroditic individuals, and therefore, a male sterile line (female parent)-purple scallop (male parent) combination of which the progenies are all hermaphroditic and excellent in traits can be bred by use of a method of establishing a plurality of backcross families and performing a combining ability test; the purple scallop line in the combination is capable of restoring the male fertility of the male sterile line, and then the restorer line of the male sterile line of the bay scallop-purple scallop hybrids can be obtained; 4) the male sterile and ovum fertile breeding scallops can be produced at a large scale by utilizing the male sterile line-maintainer line hybridization of the bay scallop-purple scallop hybrids; the male sterile breeding scallops are hybridized with the sperms of the corresponding restorer line to realize convenient, efficient and large-scale production of the commercial fingerlings of the bay scallop-purple scallop hybrids, and the obtained commercial fingerlings of the bay scallop-purple scallop hybrids have remarkable advantages in growth, individual size and temperature tolerance. 
         [0013]    The establishment method of the male sterile line, the maintainer line and the restorer line of the bay scallop-purple scallop hybrids of the present invention is as follows: 
         [0014]    1) Screening of the male sterile individuals of the bay scallop-purple scallop hybrids and the breeding of the male parents thereof: the excellent individuals of the bay scallops and the purple scallops are maturated synchronously; the bay scallops and the purple scallops are induced to spawn by use of conventional methods of the purple scallops drying in the shade and thermal stimulus, and the ova of the bay scallops and the purple scallops are collected, respectively; meanwhile, the spermiation of the purple scallops is induced, and the sperms of the purple scallops are obtained through filtering by use of a 500-mesh boulting cloth; then, an appropriate amount of purple scallop sperms are added to the ova of the bay scallops, and after the fertilized ova develop normally, the first filial generation families of the bay scallop-purple scallop hybrids (obtained by fertilizing the ova of the bay scallops by the sperms of the purple scallops) can be obtained for selecting male sterile individuals; meanwhile, the ova of the purple scallops are fertilized by the sperms from the same purple scallops to establish the self-fertilization families of the purple scallops. Due to an extremely low ratio of the male sterile individuals in the hybrid first filial generation, plenty of hybrid first filial generation families need to be established, whereby the male sterile individuals are found out for breeding the male sterile line described below. 
         [0015]    2) The breeding of the male sterile line of the bay scallop-purple scallop hybrids: the male sterile individuals in the first filial generation families of the bay scallop-purple scallop hybrids are selected, and then maturated synchronously with excellent individuals in the male parent purple scallop self-fertilization families; after the gonads are mature, the scallops of the hybrid first filial generation are induced to spawn by use of the conventional methods of the purple scallops drying in the shade and thermal stimulus and the ova are collected; meanwhile, the spermiation of the purple scallops is induced, and the sperms of the purple scallops are obtained through filtering by use of the 500-mesh boulting cloth; the obtained ova of the hybrid first filial generation are fertilized by the sperms of the purple scallops, and the fertilized ova developing normally are collected to establish backcross families, and meanwhile, the semen donating purple scallops are self-fertilized to establish self-fertilization families; in next year, the backcross families and the male parent purple scallop self-fertilization families thereof are maturated; the individuals still male sterile in the backcross families are selected and stimulated to spawn by use of a conventional purple scallop spawning induction method, and the sperms of the male parent purple scallop self-fertilization families thereof are adopted for continuous backcrossing, and meanwhile, the semen donating purple scallops are still self-fertilized continuously to establish the self-fertilization families; afterwards, continuous backcross breeding is carried out by use of the same method every year until the backcross progenies are all male sterile and ovum fertile individuals, and therefore, the male sterile line of the bay scallop-purple scallop hybrids is obtained. The male sterile line is the core line of the three-line supporting breeding system under the premise that the purpose of establishing the male sterile line of the bay scallop-purple scallop hybrids is to provide plenty of male stile breeding scallops for the production of the hybrid scallop fingerlings, and therefore, a large quantity of unfertilized ova can be obtained conveniently and efficiently at a large scale. 
         [0016]    3) The breeding of the maintainer line of the bay scallop-purple scallop hybrids: the purple scallop self-fertilization families capable of continuously keeping the male sterile characteristic of the progenies of the male sterile line are self-fertilized by use of a conventional purple scallop breeding method for multiplication, thereby obtaining the maintainer line of the male sterile line. The maintainer line plays a major role in providing sperms for breeding the male sterile line, and is a male parent line for the passage of the male sterile line. 
         [0017]    4) The breeding of the restorer line of the bay scallop-purple scallop hybrids: wherein after the male sterile line (female parent)-maintainer line (male parent) combination is obtained, excellent male sterile and ovum fertile scallops produced by use of the male sterile line-maintainer line are selected, and then maturated to spawn, and then the ova are fertilized by the sperms of different purple scallops excellent in traits to establish a large quantity of backcross families; meanwhile, the semen donating purple scallops are self-reproduced to establish the self-fertilization families; the growth and survival conditions of the hybrid progenies are measured and the combining ability is tested; starting from the second year, the backcross families having excellent traits and containing hermaphroditic scallops are selected according to a combining ability test result and gonadal development conditions every year, and the breeding scallops of the male sterile line correlated to the backcross families are continuously backcrossed with the sperms of the semen donating purple scallop self-fertilization families to establish the backcross families until the backcross families all are hermaphroditic and excellent in traits; then, the semen donating purple scallop self-fertilization families are self-fertilized by use of the conventional scallop breeding method for multiplication, thereby obtaining the restorer line of the male sterile line. The restorer line is used for providing sperms for fertilizing the ova of the male sterile line to realize the breeding of excellent commercial hybrid fingerlings. 
         [0018]    5) The multiplication of the male sterile line, the maintainer line and the restorer line of the bay scallop-purple scallop hybrids: according to the establishment method provided by the present invention, the male sterile line and the maintainer line of the bay scallop-purple scallop hybrids are hybridized to breed the next generation of the male sterile line scallops of the bay scallop-purple scallop hybrids, thereby realizing the multiplication of the male sterile line; the maintainer line and the restorer line both are purple scallop lines that are hermaphroditic and develop normally, and therefore, the next-generation maintainer line and the next-generation restorer line are bred by use of the conventional scallop population self-fertilization method, respectively. According to the establishment method, the male sterile line, the maintainer line and the restorer line of the bay scallop-purple scallop hybrids are established, and the multiplication methods of the various lines are established to realize continuous utilization; in other words, each line can be extended every year and used for the production of the following commercial fingerlings of the bay scallop-purple scallop hybrids. 
         [0019]    6) A method for producing the commercial fingerlings of the bay scallop-purple scallop hybrids by use of the three-line supporting breeding system: firstly, the breeding scallops of the male sterile line and the restorer line of the bay scallop-purple scallop hybrids are selected in the ratio of 5:1; after the breeding scallops are maturated by use of the conventional method, the breeding scallops of the male sterile line are stimulated to spawn and the breeding scallops of the restorer line are stimulated to spawn and discharge semen, and then the semen-ovum mixed liquid of the restorer line is filtered by use of the 500-mesh boulting cloth to obtain the semen of the restorer line; next, the semen of the restorer line are added to a spawning pond and stirred; the most appropriate amount of the sperms added is that each ovum is surrounded by 5-6 sperms; finally, incubation is carried out by use of a conventional method to obtain the commercial fingerlings of the bay scallop-purple scallop hybrids. 
         [0020]    The establishment method of the three-line supporting breeding system of the present invention is also applied to the breeding practices of the Argopecten hybrid scallops such as purple scallop-bay scallop hybrids (the hybridization progenies of the ova of the purple scallops and the sperms of the bay scallops), purple scallop-Mexico Gulf scallop hybrids (the hybridization progenies of the ova of the purple scallops and the sperms of the Mexico Gulf scallops) and Mexico Gulf scallop-purple scallop hybrids (the hybridization progenies of the ova of the purple scallops and the sperms of the Mexico Gulf scallops), and applied to the establishment of large-scale production methods of the commercial fingerlings of the hybrid scallops. 
         [0021]    The method of the present invention is also applied to interspecific hybridization breeding of other hermaphroditic scallops, such as the interspecific hybridization of Pecten scallops; the basic method of the present method is also applicable to the interspecific hybridization breeding of other hermaphroditic invertebrates. 
         [0022]    The male sterile line, the maintainer line and the restorer line of the bay scallop-purple scallop hybrids established in the present invention belong to the three-line supporting breeding system of the scallops established in animalia for the first time and can be taken as a major breakthrough in the animal breeding technology. The present invention effectively removes the barrier of self-fertilization in the hybridization process of the hermaphroditic scallops and realizes the obtaining of complete hybridization progenies at a low cost and in a large scale, and therefore, the hybrid advantages can be utilized thoroughly to enable the cultured commercial fingerlings of the bay scallop-purple scallop hybrids to have the characteristics of both the bay scallops and the purple scallops and to show remarkable advantages in the aspects of growth, individual size and temperature tolerance in contrast with the bay scallops; hence, the bay scallop-purple scallop hybrids can be successfully bred in northern sea regions such as Qingdao and Dalian, and its yield in the current year can be increased by more than 50% in contrast with the bay scallops. 
     
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       [0023]    The present invention establishes a three-line supporting breeding system, comprising a male sterile line, a maintainer line and a restorer line, of bay scallop-purple scallop hybrids and also establishes a method for producing the commercial fingerlings of the bay scallop-purple scallop hybrids by use of a three-line supporting breeding system; the specific steps are as follows: 
       Embodiment 1 
       [0024]    1) Screening of the male sterile individuals of the bay scallop-purple scallop hybrids and the breeding of the male parents thereof: in the first year, 50 gonadal maturated bay scallops and 50 purple scallops are selected; after drying in the shade and stimulus for 30 minutes, each scallop is put into an independent container to which 23° C. seawater is added in advance for spawning and spermiation; the ova of each bay scallop and the sperms and the ova of each purple scallop are collected independently; little semen from a single purple scallop is added to the ovum suspension liquid of each bay scallop and stirred so that the sperms and the ova can be mixed evenly; each ovum is surrounded by 5-6 sperms through observation under a microscope, and the fertilized ova are put in a dark environment for incubation, thereby obtaining a bay scallop-purple scallop hybrid first filial generation family. At least 20 such hybrid families are established by use of such a method; meanwhile, the sperms and the ova of the semen donating purple scallops are mixed for fertilization to establish a corresponding number of purple scallop self-fertilization families; finally, larva culture, fingerling protection and development are carried out by use of a conventional scallop breeding method for the screening of the male sterile individuals. 
         [0025]    2) The breeding of the male sterile line of the bay scallop-purple scallop hybrids: in the spring of the second year, the bay scallop-purple scallop hybrid first filial generation families are maturated, and then 50 male sterile individuals excellent in traits are selected and stimulated to spawn by use of a conventional purple scallop spawning induction method, and the ova are fertilized by the sperms of the male parent purple scallops thereof, respectively; the normally fertilized and developed ova are collected to establish the backcross families, and meanwhile, the sperm providing purple scallops are self-fertilized to establish the self-fertilization families, whereby at least 20 backcross families and corresponding male parent purple scallop self-fertilization families are established, and larva culture, fingerling protection and development are carried out by use of the conventional purple scallop breeding method; in the spring of the third year, after the backcross families and the purple scallop self-fertilization families are maturated, 50 male sterile individuals having excellent traits in the backcross families are selected and backcrossed with the self-fertilization progeny sperms of the male parent purple scallops thereof, and then the normally fertilized and developed ova are collected for continuously establishing the backcross families, and meanwhile, the self-fertilization families of the purple scallops are bred continuously; more than 20 backcross families having excellent traits and corresponding purple scallop self-fertilization families thereof are selectively established; afterwards, the male sterile scallops having excellent traits are selected to be backcrossed with the self-fertilization families of the male parent purple scallops thereof by use of the same method every year until all the individuals of the backcross progenies show excellent traits and are male sterile and ovum fertile; as a result, the male sterile line of the bay scallop-purple scallop hybrids is obtained. 
         [0026]    3) The breeding of the maintainer line of the bay scallop-purple scallop hybrids: the male parent purple scallops capable of enabling all the individuals of the backcross progenies of the male sterile individuals to be male sterile and ovum fertile are self-fertilized by use of the conventional scallop breeding method for great reproduction, thereby obtaining the maintainer line of the male sterile line of the bay scallop-purple scallop hybrids. 
         [0027]    4) The breeding of the restorer line of the bay scallop-purple scallop hybrids: 50 male sterile and ovum fertile large individual scallops produced from the bred male sterile line and maintainer line are selected, and maturated to spawn, and the ova are fertilized by the sperms of the different purple scallops to establish at least 20 backcross families; meanwhile, the semen donating purple scallops are self-fertilized to establish the self-fertilization families, and the growth and survival conditions of the backcross progenies are measured and the combining ability is tested; starting from the second year, the backcross families having excellent traits and containing the hermaphroditic scallops are selected according to the combining ability test result and the gonadal development conditions every year, and the breeding scallops of the male sterile line correlated to the backcross families are continuously backcrossed with the sperms of the semen donating purple scallop self-fertilization families to establish the backcross families until the backcross families all are hermaphroditic and excellent in traits; then, the semen donating purple scallop self-fertilization families are self-fertilized for multiplication, thereby obtaining the restorer line of the male sterile line of the bay scallop-purple scallop hybrids. The restorer line is used for large-scale production of the commercial fingerlings of the bay scallop-purple scallop hybrids. 
         [0028]    5) A method for producing the commercial fingerlings of the bay scallop-purple scallop hybrids by use of the three-line supporting breeding system: the breeding scallops of the male sterile line and the restorer line of the bay scallop-purple scallop hybrids are hybridized for multiplying the male sterile line scallops of the bay scallop-purple scallop hybrids, and meanwhile, the restorer line is multiplied through self-fertilization by use of the conventional scallop breeding method; during breeding in spring, the breeding scallops of the male sterile line and the restorer line are selected in the ratio of 5:1 and maturated; then, breeding scallops of the male sterile line are stimulated to spawn in a spawning pond, and the breeding scallops of the restorer line are stimulated to discharge semen in a bucket, and the restorer line purple scallop semen containing no ovum is obtained through filtering by use of the 500-mesh boulting cloth; the semen of the restorer line is uniformly splashed to the spawning pond and stirred immediately; a sample is taken any time for observing the fertilization condition under the microscope; the most appropriate amount of the semen added is that each ovum is surrounded by 5-6 sperms; finally, the fertilized ova are incubated by use of the conventional method and develop to obtain the commercial fingerlings of the bay scallop-purple scallop hybrids. 
       Embodiment 2 
       [0029]    At the end of March in 2008, the gonadal maturated bay scallops were picked up and subjected to thermal stimulus to obtain the ova of the bay scallops; the ova of the bay scallops were fertilized by the sperms of the purple scallops to obtain the hybrid first filial generation fingerlings of the bay scallops and the purple scallops, and the fingerlings were cultured to develop. In the spring of 2009, the scallops of the hybrid first filial generation were maturated, and then scallops large in size and developed only in female parts were selected therefrom and dried in the shade for 30 minutes; next, the scallops were put into the container containing 23° C. seawater to be stimulated to spawn, and the ova were fertilized by the sperms from a plurality of purple scallops together, whereby the backcross population of the first-filial generation bay scallop-purple scallop hybrids and the purple scallops were obtained. After the backcross population was maturated in the spring of 2010, most individuals are hermaphroditic, accompanied with less than 10% of male sterile individuals. 
         [0030]    Continuously, the male sterile individuals were backcrossed with the sperms of the self-fertilization progenies of the male parent purple scallops thereof; whereby the male sterile line (female parent)-maintainer line (male parent) combination of which the progenies were all male sterile and ovum fertile could be obtained through one-generation to multiple-generation breeding, and therefore, the male sterile line and the maintainer line could be obtained, respectively. After gonadal maturation, spawning induction was performed on the male sterile line scallops by use of a conventional purple scallop spawning induction method to obtain a large quantity of unfertilized ova, and the unfertilized ova were fertilized by the sperms of the maintainer line so that the male sterile line breeding scallops for producing the commercial fingerlings of the bay scallop-purple scallop hybrids could be obtained at a large scale. 
         [0031]    The ova of the male sterile line scallops in the combination were fertilized by the sperms of different unrelated purple scallops to establish at least  20  backcross families, and the combining ability was tested; the families of which the progenies contain the hermaphroditic scallops were selected, and the female parent male sterile line breeding scallops thereof were continuously fertilized by the sperms of the semen donating purple scallop self-fertilization families; continuous breeding was performed according to the growth traits and the gonad development conditions until all the backcross progenies were hermaphroditic and excellent in traits, and the restorer line purple scallop families that could be fertilized to produce male sterile line progenies all hermaphroditic and excellent in traits could be obtained. 
         [0032]    Finally, after the gonads of the obtained male sterile line breeding scallops of the bay scallop-purple scallop hybrids were maturated, a large quantity of unfertilized ova were obtained by use of the conventional purple scallop spawning induction method and fertilized by the sperms of the restorer line to produce the commercial fingerlings of the bay scallop-purple scallop hybrids at a large scale. 
       Embodiment 3 
       [0033]    In the spring of 2010, the male sterile individuals in the hybrid first filial generation of the ova of the bay scallops and the sperms of the purple scallops established in 2009 were selected, and maturated and stimulated to spawn; the ova were fertilized by the sperms of the purple scallops to establish 8 backcross families, and the backcross families were cultured. In the spring of 2011, it was discovered through maturation that most individuals of all the families were hermaphroditic and the gonads of few individuals were not developed, which proved that the restorer line of the bay scallop-purple scallop hybrids could be bred by backcrossing the purple scallops with the male sterile individuals in the first filial generation of the bay scallop-purple scallop hybrids. 
       Embodiment 4 
       [0034]    In 2012, after a stimulus was applied to the male sterile individuals only developed in female parts in the first filial generation families of the bay scallop-purple scallop hybrids, 20 male sterile individuals among them spawned, and the ova were backcrossed with the sperms of one individual purple scallop to successfully obtain 2 backcross families; when harvesting in the middle of November in 2012, compared with the bay scallops in the corresponding period, the shell height, the shell length and the individual weight of one backcross family were increased by 46.3%, 45.7%, 32.3% and 134.9%, respectively, and after maturation in the spring of 2013, it was discovered that the progenies of the backcross family were wall hermaphroditic; it indicated that the restorer line of the male sterile line of the bay scallop-purple scallop hybrids could be successfully bred by backcrossing the sperms of the purple scallops with the male sterile individuals; the shell height, the shell length and the individual weight of the other backcross family were increased by 28.2%, 29.5%, 16.4% and 74.0%, respectively, and after maturation in the spring of 2013, it was discovered that the progenies of the backcross family most were developed in female parts; it indicated that the male sterile line of the bay scallop-purple scallop hybrids and the maintainer line thereof could be successfully bred by backcrossing the sperms of the purple scallops with the male sterile individuals. 
       Embodiment 5 
       [0035]    In 2013 and 2014, 12 hybrid first filial generation families of the ova of the bay scallops and the sperms of the purple scallops were established by use of the imported bay scallops and purple scallops, and the self-fertilization families of the semen donating purple scallops are established; according to the method of embodiment 1, the male sterile families of the bay scallop-purple scallop hybrids and the corresponding maintainer line and restorer line thereof can be bred within 1-3 years, and therefore, the commercial production of the fingerlings of the bay scallop-purple scallop hybrids is realized. 
       Embodiment 6 
       [0036]    The present invention is applied to the establishment and the application of the male sterile line, the maintainer line and the restorer line of the bay scallop-purple scallop hybrids 
         [0037]    The establishment method of the male sterile line, the maintainer line and the restorer line disclosed by the present invention is also applied to the breeding of purple scallop-bay scallop hybrids (the hybridization progenies of the ova of the purple scallops and the sperms of the bay scallops) and applied to the establishment of a large-scale production method of the commercial fingerlings of the purple scallop-bay scallop hybrids. 
         [0038]    Firstly, the purple scallops and the bay scallops are selected to be maturated simultaneously, and stimulated to spawn and discharge semen simultaneously; the ova of the purple scallops and the sperms and ova of the bay scallops are collected, respectively; the ova of the purple scallops are fertilized by the sperms of the bay scallops to establish purple scallop-bay scallop hybrid first filial generation families for selecting the male sterile individuals; meanwhile, the sperms and ova of the bay scallops are mixed for fertilization to establish bay scallop self-fertilization families; in the second year, the male sterile individuals are selected from the purple scallop-bay scallop hybrid first filial generation families and fertilized by the sperms of the bay scallops; if the fertilized ova develop normally, the backcross families are established for continuously breeding the male sterile line, and meanwhile, the male parent bay scallops are self-fertilized for establishing the self-fertilization families; in this way, through one generation to multiple generation selection, when the backcross progenies all are male sterile, the male sterile line of the purple scallop-bay scallop hybrids and the corresponding maintainer line are obtained. 
         [0039]    A plurality of large individual scallops in the male sterile line of the purple scallop-bay scallop hybrids are selected and simulated to spawn, and then the ova are fertilized by the sperms of a plurality of unrelated bay scallops; if the backcross families all are hermaphroditic scallops, a male sterile line-restorer line combination is obtained only through one generation selection; if the backcross families are partially hermaphroditic, the male sterile scallops are continuously backcrossed with the sperms of the corresponding bay scallop self-fertilization families to establish the backcross families, and meanwhile, the self-fertilization families of the male parent bay scallops are continuously established for next generation breeding; after one generation or multiple generation breeding, when the backcross progenies are all hermaphroditic, the restorer line of the male sterile line of the purple scallop-bay scallop hybrids is obtained. 
         [0040]    The ova of the male sterile line of the purple scallop-bay scallop hybrids are hybridized with the sperms of the maintainer line, thereby realizing efficient, convenient and large-scale production of the male sterile breeding scallops of the purple scallop-bay scallop hybrids; the male sterile breeding scallops of the purple scallop-bay scallop hybrids are hybridized with the sperms of the restorer line to realize efficient, convenient and large-scale production of the fingerlings of the purple scallop-bay scallop hybrids. 
       Embodiment 7 
       [0041]    The present invention is applied to the establishment and the application of the male sterile line, the maintainer line and the restorer line of purple scallop-Mexico Gulf scallop hybrids. 
         [0042]    The establishment method of the male sterile line, the maintainer line and the restorer line disclosed by the present invention is also applied to the breeding of the purple scallop-Mexico Gulf scallop hybrids (the hybridization progenies of the ova of the purple scallops and the sperms of the Mexico Gulf scallops) and applied to the establishment of a large-scale production method of the commercial fingerlings of the purple scallop-Mexico Gulf scallop hybrids. 
         [0043]    Firstly, the purple scallops and the Mexico Gulf scallops are selected to be maturated simultaneously, and stimulated to spawn and discharge semen simultaneously; the ova of the purple scallops and the sperms and ova of the Mexico Gulf scallops are collected, respectively; the ova of the purple scallops are fertilized by the sperms of the Mexico Gulf scallops to establish purple scallop-Mexico Gulf scallop hybrid first filial generation families for selecting the male sterile individuals; meanwhile, the sperms and ova of the Mexico Gulf scallops are mixed for fertilization to establish Mexico Gulf scallop self-fertilization families; in the second year, the male sterile individuals are selected from the purple scallop-Mexico Gulf scallop hybrid first filial generation families and fertilized by the sperms of the Mexico Gulf scallops; if the fertilized ova develop normally, the backcross families are established for continuously breeding the male sterile line, and meanwhile, the male parent Mexico Gulf scallops are self-fertilized for establishing the self-fertilization families; in this way, through one generation to multiple generation selection, when the backcross progenies all are male sterile, the male sterile line of the purple scallop-Mexico Gulf scallop hybrids and the corresponding maintainer line thereof are obtained. 
         [0044]    A plurality of large individual scallops in the male sterile line of the purple scallop-Mexico Gulf scallop hybrids are selected and simulated to spawn, and then the ova are fertilized by the sperms of a plurality of unrelated Mexico Gulf scallops; if the backcross families all are hermaphroditic scallops, the male sterile line-restorer line combination is obtained only through one generation selection; if the backcross families are partially hermaphroditic, the male sterile scallops are continuously backcrossed with the sperms of the corresponding Mexico Gulf scallop self-fertilization families to establish the backcross families, and meanwhile, the self-fertilization families of the male parent Mexico Gulf scallops are continuously established for next generation breeding; after one generation or multiple generation breeding, when the backcross progenies are all hermaphroditic, the restorer line of the male sterile line of the purple scallop-Mexico Gulf scallop hybrids is obtained. 
         [0045]    The ova of the male sterile line of the purple scallop-Mexico Gulf scallop hybrids are hybridized with the sperms of the maintainer line, thereby realizing efficient, convenient and large-scale production of the male sterile breeding scallops of the purple scallop-Mexico Gulf scallop hybrids; the male sterile breeding scallops of the purple scallop-Mexico Gulf scallop hybrids are hybridized with the sperms of the restorer line to realize efficient, convenient and large-scale production of the fingerlings of the purple scallop-Mexico Gulf scallop hybrids. 
       Embodiment 8 
       [0046]    The present invention is applied to the establishment and the application of the male sterile line, the maintainer line and the restorer line of Mexico Gulf scallop-purple scallop hybrids. 
         [0047]    The establishment method of the male sterile line, the maintainer line and the restorer line disclosed by the present invention is also applied to the breeding of the Mexico Gulf scallop-purple scallop hybrids (the hybridization progenies of the ova of the Mexico Gulf scallops and the sperms of the purple scallops) and applied to the establishment of a large-scale production method of the commercial fingerlings of the Mexico Gulf scallop-purple scallop hybrids. 
         [0048]    Firstly, the purple scallops and the Mexico Gulf scallops are selected to be maturated simultaneously, and stimulated to spawn and discharge semen simultaneously; the ova of the Mexico Gulf scallops and the sperms and ova of the purple scallops are collected, respectively; the ova of the Mexico Gulf scallops are fertilized by the sperms of the purple scallops to establish Mexico Gulf scallop-purple scallop hybrid first filial generation families for selecting the male sterile individuals; meanwhile, the sperms and ova of the purple scallops are mixed for fertilization to establish purple scallop self-fertilization families; in the second year, the male sterile individuals are selected from the Mexico Gulf scallop-purple scallop hybrid first filial generation families and fertilized by the sperms of the purple scallops; if the fertilized ova develop normally, the backcross families are established for continuously breeding the male sterile line, and meanwhile, the male parent purple scallops are self-fertilized for establishing the self-fertilization families; in this way, through one generation to multiple generation selection, when the backcross progenies all are male sterile, the male sterile line of the Mexico Gulf scallop-purple scallop hybrids and the corresponding maintainer line thereof are obtained. 
         [0049]    A plurality of large individual scallops in the male sterile line of the Mexico Gulf scallop-purple scallop hybrids are selected and simulated to spawn, and then the ova are fertilized by the sperms of a plurality of unrelated purple scallops; if the backcross families all are hermaphroditic scallops, the male sterile line-restorer line combination is obtained only through one generation selection; if the backcross families are partially hermaphroditic, the male sterile scallops are continuously backcrossed with the sperms of the corresponding purple scallop self-fertilization families to establish the backcross families, and meanwhile, the self-fertilization families of the male parent purple scallops are continuously established for next generation breeding; after one generation or multiple generation breeding, when the backcross progenies are all hermaphroditic, the restorer line of the male sterile line of the Mexico Gulf scallop-purple scallop hybrids is obtained. 
         [0050]    The ova of the male sterile line of the Mexico Gulf scallop-purple scallop hybrids are hybridized with the sperms of the maintainer line, thereby realizing efficient, convenient and large-scale production of the male sterile breeding scallops of the Mexico Gulf scallop-purple scallop hybrids; the male sterile breeding scallops of the Mexico Gulf scallop-purple scallop hybrids are hybridized with the sperms of the restorer line to realize efficient, convenient and large-scale production of the fingerlings of the Mexico Gulf scallop-purple scallop hybrids.