Current Status and Future Prospects of New Aquatic Variety Research and Development in China
Aquatic improved varieties generally refer to some original species and new aquatic varieties with excellent economic traits and production performance. At present, although the research and development of new aquatic varieties in China is stimulated by favorable factors such as certain policy support, technical guarantees, and social demand, it still faces constraints such as the decline of germplasm resources, dependence on imports for important seed sources, an immature research and development system, and insufficient extension capacity. The road ahead for future development is long and arduous.
Basic Situation of New Aquatic Variety Research and Development
Development History
Although China's aquaculture industry has a long history of development, dating back to the Shang and Zhou dynasties, about 3,000 years ago, variety research and development work only began in the 1960s, initially involving only conscious artificial improvement of some cultured varieties. The development history can be roughly divided into three stages: The first stage, before 1957, was the stage of extensive fry and fingerling production. The supply of fry and fingerlings mainly relied on collection and cultivation from natural waters, and in 1957 the collection volume of fry and fingerlings reached 23.4 billion. The second stage was the stage of breaking through artificial breeding technology. After China achieved breakthroughs in artificial breeding of Chinese carps in 1958, artificial breeding technologies for a large number of wild species and domesticated species were broken through. At the same time, introducing species from abroad for trial cultivation also formed a certain industrial scale. The third stage was the initial stage of breeding and research and development. With the rapid development of the aquaculture industry, in the late 1980s and early 1990s, problems such as frequent disease outbreaks caused by the degradation of cultured varieties became prominent, creating an urgent need for research and development of new aquatic varieties. In 1991, the National Aquatic Original Species and Improved Variety Approval Committee was established, and the approval of new aquatic varieties was formally placed on the agenda. In the 1990s, several new aquatic varieties were bred, including Xingguo red carp, Hebao red carp, and Pengze crucian carp. From then on, the research and development of new aquatic varieties in China began.
Breeding Research and Development Technologies
At present, China's aquatic breeding research and development technologies mainly include selective breeding technology, crossbreeding technology, cell engineering breeding technology, and molecular breeding technology. The most studied and most widely used is group selection technology. After 2000, China introduced and established multi-trait composite technology, which was rapidly promoted and applied in multiple cultured varieties. This technology establishes families on a large scale, marks and identifies families and individuals, uses pedigree and measurement information such as the individual itself, siblings, ancestors, and offspring, conducts genetic evaluation through restricted maximum likelihood (REML) and best linear unbiased prediction (BLUP), selects broodstock parents according to a comprehensive selection index, and strictly selects and mates at the family and individual levels, solving the problem of inbreeding and the resulting germplasm degradation.
Crossbreeding makes full use of complementary effects among populations, especially heterosis. So-called heterosis refers to the phenomenon in which hybrids produced by crossing different populations are superior to the average of the two parent populations to a certain extent in vitality, growth vigor, and production performance. In aquaculture, there are two methods of crossbreeding: intraspecific crossing and interspecific crossing. The main target traits of intraspecific crossing research are growth rate and stress resistance, with the goal of breeding new varieties with high yield and strong stress resistance. Interspecific crossing can be used to increase growth rate, regulate sex ratio, breed sterile populations, improve meat quality, enhance disease resistance, enhance adaptability to extreme environments, and improve important economic traits.
Cell engineering breeding technology and molecular breeding technology are relatively novel technologies. Cell engineering breeding technology is a breeding technology that carries out genetic manipulation at the cellular and chromosomal levels to improve varieties, and it has been one of the research hotspots in recent years. Research on cell engineering breeding technology for aquatic organisms currently mainly includes polyploid breeding, gynogenesis, monosex fry and fingerling cultivation, cell fusion, and nucleocytoplasmic hybridization (nuclear transplantation). In molecular biology technology, explorations and studies have been carried out on molecular marker-assisted breeding technology and whole-genome breeding technology, and related technical systems have been initially established. At present, research on molecular markers of aquaculture organisms mostly aims to indirectly assist selective breeding by screening various molecular markers associated with target traits.
Research and Development Achievements
According to statistics, several thousand species of aquatic organisms have been reported in China, of which more than 170 aquatic species can be cultured, and more than 40 are major economically cultured varieties, mainly including the "four major Chinese carps", carp, crucian carp, bream, mandarin fish, tilapia, eel, sea bream, snakehead, perch, catfish, yellow catfish, olive flounder, grouper, longsnout catfish, large yellow croaker, salmon and trout, turbot, sturgeon, bagrid catfish, prawn, crayfish (red swamp crayfish), scallop, oyster, clam, pearl oyster, abalone, kelp, laver, wakame, sea cucumber, sea urchin, Chinese softshell turtle, and so on. These are currently the main targets of new aquatic variety research and development in China.
As of 2015, there were 156 new aquatic varieties announced by the Ministry of Agriculture of China. Apart from 30 introduced species, there were 126 independently bred new aquatic varieties, including 76 selectively bred varieties, accounting for 49%; 45 hybrid varieties, accounting for 29%; and 5 other types, accounting for 3%. Except for grass carp, important cultured species have basically achieved breakthroughs in new varieties. There were 87 fish varieties, accounting for 56%; 14 shrimp varieties, accounting for 9%; 5 crab varieties, accounting for 3%; 21 shellfish varieties, accounting for 13.5%; 21 algae varieties, accounting for 13.5%; and 8 other species, accounting for 5%. They mainly show the following characteristics:
First, the average annual number of bred varieties has gradually increased. Before 2000, a cumulative total of 40 were completed; from 2001 to 2005, 21 were completed; from 2006 to 2010, 39 were completed; and from 2011 to 2014, 56 were completed (see Figure 1 for details). In recent years, the number of shellfish and algae varieties has increased significantly. Among the 42 new shellfish and algae varieties, 25 were completed in the past 4 years.
Second, some varieties have obvious advantages. There are relatively many new varieties of carp, crucian carp, tilapia, and kelp. For carp, 4 introduced species were registered and 24 were independently bred; for crucian carp, there were no registered introduced species and 12 were independently bred; for tilapia, 3 introduced species were registered and 8 were independently bred; for kelp, there were no registered introduced species and 10 were independently bred. There are also 5 or more new aquatic varieties for Pacific white shrimp. In addition, series varieties have been continuously introduced, such as GIFT tilapia - New GIFT tilapia - Jili tilapia, Jian carp - Jinxin carp - Jinxin carp No. 2, "Zhongke Red" bay scallop - bay scallop "Zhongke No. 2", "Penglai Red" scallop - Zhikong scallop "Penglai Red No. 2", kelp "Dongfang No. 1" - "Dongfang No. 2" - "Dongfang No. 3" - "Dongfang No. 6" - "Dongfang No. 7", Pyropia haitanensis "Shenfu No. 1" - "Shenfu No. 2"; Pyropia yezoensis "Sutong No. 1" - "Sutong No. 2"; wakame "Haibao No. 1" - "Haibao No. 2", and so on.
Third, research and development entities are diversified. Statistics show that the first breeding units of new varieties (including introduced species) basically cover the main research institutions in China's aquatic industry, including research institutes, aquatic colleges and universities, aquatic extension agencies, and aquatic enterprises, numbering 80, 40, 7, and 29 respectively. Research and development entities are mainly research institutes and colleges and universities, and in recent years enterprise participation has increased. There were 93 varieties independently bred by 1 unit, accounting for 60%; 63 varieties jointly bred by 2 or more units, accounting for 40%; and 14 varieties jointly bred by 3 or more units, less than 10%.
Current Status and Problems of Utilization of Introduced Species
China is one of the countries with the most aquatic species introductions in the world. According to incomplete statistics, China has introduced more than 140 aquaculture species, including more than 90 fish species, more than 10 shrimp species, more than 10 shellfish species, more than 10 algae species, and more than 10 other species, with 30 registered as new aquatic varieties. In addition, 23 new varieties were obtained through direct use of introduced species in research and development. It can be said that one third of China's new aquatic varieties originate from introduced species. The introduction of aquatic fry and fingerlings has played an important role in promoting the development of China's aquaculture industry. Among them, tilapia, turbot, eel, Pacific white shrimp, and scallops (bay scallop and Japanese scallop) have become important aquatic products in China, creating enormous industrial value. In 2013, China's aquaculture output of tilapia reached 1.6577 million tons, and the aquaculture output of Pacific white shrimp reached 1.4298 million tons. Starting in 2009, the state no longer recognized introduced species.
Introduction has promoted the development of the aquaculture industry, but it cannot solve the fundamental problems in the development of China's aquatic fry and fingerlings. At present, introduction work has many illegal introductions and few legal introductions; many blind introductions and few scientific demonstrations; many without quarantine and few disease prevention treatments; much eager promotion and little careful evaluation; and many repeated introductions and little conservation and selective breeding. Introduction inevitably carries the following risks: First, introduction leaves one controlled by others. Not only are prices monopolistically controlled, but introduced species generally show obvious degradation starting from the second generation and cannot continue to be used. Second, it faces the threat of invasive alien species. Aquatic invasive animals and plants that have already shown harm include crayfish, crocodiles, golden apple snails, water hyacinth, and so on. Third, introduced species carry parasites and diseases. It has been reported that many diseases causing major losses in China's aquaculture were caused by passively introduced viruses, such as white spot syndrome baculovirus and Taura syndrome virus in shrimp, and iridovirus in olive flounder.
Achievement Extension
At present, the extension entities of new aquatic varieties in China are basically centered on breeding units and oriented by market demand. Breeding units directly or indirectly sell fry and fingerlings of new varieties to farmers. Varieties with good culture performance are favored by farmers, which in turn stimulates increased sales of fry and fingerlings and gradually expands the extension effect. A number of varieties such as Jian carp, Pengze crucian carp, Wuchang bream "Pujiang No. 1", and Chinese shrimp "Huanghai No. 1" have been tested in culture and have shown good extension results. Their visibility has continued to increase, they occupy a certain market, and their production contribution has continued to rise. The Ministry of Agriculture releases main recommended variety technologies every year, guiding all localities to further support the extension of varieties with certain potential from the policy level. According to survey research, there are still some varieties that, due to limitations in the breeding unit's own extension capacity or factors such as variety specificity, are shelved immediately after obtaining a new variety certificate and cannot exert production effects.
Prospects for New Aquatic Variety Research and Development
Research and Development Challenges
Compared with crop farming and animal husbandry, China's aquaculture improved variety development is still relatively backward, and compared with the channel catfish and Pacific white shrimp industries in the United States and the Atlantic salmon industry in Norway, the gap is still very large. The 55% coverage rate of aquatic improved varieties and the 25% genetic improvement rate still leave considerable room for improvement. The development of modern aquatic seed industry has a very urgent demand for new aquatic varieties. However, at present, China's research and development of new aquatic varieties faces some challenges. First, the status of aquatic germplasm resources is worrying. Deterioration of the water ecological environment and overfishing of natural fishery resources have led to a sharp decline in the biomass of most aquatic organisms and a reduction in genetic diversity. Conserved resources show signs of germplasm degradation. Second, the foundation for improved variety research and development is still relatively weak. Improved variety research and development requires sustained support in time, manpower, and financial resources. There are too many varieties, and the broad scope weakens the strength of investment in research and development for a single variety. In addition, for some cultured varieties such as eel, artificial breeding of fry and fingerlings has not yet been achieved. Third, there are hidden dangers of dependence on introduced species. Fourth, there is a lack of synergy among breeding entities. There are many research and development units for a certain variety, multilateral cooperation is obviously lacking, scientific and technological resources have not been well integrated, and synergy cannot be formed, resulting in waste of resources. Fifth, there is insufficient support for the extension of research and development achievements. The cost of seed or fry production for new varieties is often higher than that of ordinary fry and fingerlings, and quality advantages are often not easy to demonstrate. Ordinary people generally only recognize price, causing the problem that improved varieties are of high quality but difficult to sell at a premium, and the initial extension of research and development achievements is difficult.
Future Prospects
On the road to building a modern aquatic seed industry and moving toward becoming a world powerhouse in aquatic seed industry, we must absorb all advanced technologies and experience at home and abroad, and on the premise of strengthening the protection and rational development of germplasm resources, establish concepts of variety development and management suited to the characteristics of China's aquaculture industry, formulate long-term research and development plans for key cultured varieties, strengthen the development, utilization, and management of introduced species, integrate social resources to gradually improve the systematic research, development, and extension of new varieties, promote the improved variety development of major cultured species in a planned and focused manner, and ultimately realize the improved variety development of the aquaculture industry and enhance the international market competitiveness of China's aquaculture products. The author believes that in the future, based on existing work, we should focus on building and improving the following five major systems:
First, a systematically improved aquatic germplasm resource conservation system.
Aquatic breeding needs to be based on abundant variety resources. Extensive collection and conservation of germplasm resources are of great value to the research and development of new aquatic varieties. Although China has already built germplasm resource protection areas, genetic breeding centers, and original and improved seed farms, protecting and conserving resources at multiple levels such as population, individual, cell, and gene; however, a complete system has not been formed overall, the informatization level of internal individual resource data is low, horizontal and vertical links are lacking among them, and various resources cannot yet be shared. In the future, the government should support the establishment of a big data support platform to complete system linkage and resource allocation. The system should focus on collecting and conserving three major categories of resources: first, germplasm materials of existing leading cultured varieties and high-quality wild species; second, excellent germplasm materials with disease resistance, cold resistance, saline-alkali tolerance, and high protein; and third, scientific research germplasm materials that maintain biodiversity and can be used for basic research.
Second, a policy support system that clearly defines the main target varieties for research and development.
Since the reform and opening up, due to the improvement of people's living standards and the development of the market economy, aquaculture varieties have continuously increased and become more and more diversified. However, breeding research and development must take into account the needs of production development and international trends in the aquatic industry. At the national level, China should focus on establishing the main target varieties for breeding and research and development of new varieties in China's aquatic seed industry and vigorously support them, trying to ensure the efficiency of fiscal fund use. The establishment of main target varieties should conform to the following principles: first, varieties that occupy a certain proportion of China's total aquaculture output; second, major domestic market consumption varieties; and third, export foreign exchange-earning varieties. The author believes that the first batch of main target varieties for aquatic research and development in China should include: large yellow croaker, tilapia, turbot, eel, grass carp, carp and crucian carp, Chinese shrimp, Pacific white shrimp, swimming crab, river crab, Japanese scallop, bay scallop, oyster, clam, kelp, and laver.
Third, a complete system for the development, utilization, and management of introduced species.
Establish and improve a nationwide management system and information system for the introduction of aquaculture varieties. Strengthen risk assessment of introduced species, strictly implement quarantine regulations, and minimize the harm of alien species to China's germplasm resources. Conduct full-process tracking management for new aquaculture varieties that China has already introduced and those to be introduced. According to industrial development, formulate medium- and long-term development plans for future introductions. Adapt introduced species to local conditions through digestion, absorption, re-innovation, and extension, and attach importance to and strengthen the protection of the local ecological environment.
Fourth, a mature new system for research and development of new varieties.
Break the pattern of fighting alone and competing with each other, and adopt strategies of strong-strong alliances and multidisciplinary operations. Starting from national and market needs for germplasm utilization and aquaculture varieties, it should be made clear that the main direction is to breed varieties with high yield, high quality, disease resistance, cold resistance, saline-alkali resistance, and adaptability to high-density culture in facility fisheries. At the same time, research should be conducted on the applied foundations and applied technologies of breeding. Each research and development team should include research institutes, enterprises, and extension departments. Each unit should perform its own duties: research institutes are responsible for formulating technical routes and tackling key difficulties, enterprises are responsible for implementing the routes and providing feedback on problems, and extension departments are responsible for research and development testing and providing feedback on market demand. A unified national platform should register and disclose information on each breeding team, ensuring that teams learn from each other's strengths to offset their weaknesses and avoiding resource conflicts.
Fifth, a complete supporting extension system for new varieties.
The state should provide corresponding financial support for the extension of new varieties to ensure that follow-up extension funds are available after new varieties are announced. Establish a well-developed publicity system and extensively carry out publicity for new varieties through media such as the internet, television, books and periodicals, newspapers, and magazines to increase market awareness. Establish extension bases with demonstrations at each level, with national, provincial, and prefecture (city)-level extension station demonstration bases as the main body, carrying out layer-by-layer demonstration and extension of new varieties to ensure that the extension industry is coordinated nationwide as a whole. Establish technical guidance and service centers, extensively carry out training on new technologies and new varieties, and provide consultation on after-sales product issues. In addition, actively guide social forces to cooperate in improved variety extension.