The grass carp (Ctenopharyngodon idella) has long been a cornerstone of freshwater aquaculture, providing a vital source of protein for millions of people. In 2023, grass carp production reached 5.941 million tons.
However, growing threats to natural grass carp populations due to human activities, habitat degradation, and overfishing have cast a shadow over the future of this industry. In a scientific review article published in the KeAi journal Reproduction and Breeding, a team of researchers from Hunan Normal University (China) and Hunan Yuelu Mountain Science and Technology Co., Ltd., summarized the key research findings on grass carp morphology, cytogenetics, molecular biology, genetic improvement of germplasm resources, and more.
The Decline of Wild Grass Carp Populations
Wild grass carp populations, once abundant in Chinese waters, have suffered a dramatic decline. Human-induced pressures, including habitat destruction, pollution, and overfishing, have pushed these fish to the brink. This alarming situation underscores the urgent need for effective conservation measures and the development of robust aquaculture practices.
The Indispensable Role of Grass Carp Germplasm
High-quality grass carp germplasm is the foundation upon which the future of grass carp aquaculture rests. It holds the key to developing improved varieties with superior growth rates, disease resistance, and adaptability to changing environmental conditions. By systematically collecting, preserving, and characterizing these valuable genetic resources, researchers and aquaculture professionals can safeguard the long-term sustainability of the industry.
Unlocking the Genetic Potential of Grass Carp
Advances in genetics and biotechnology have opened new avenues for improving grass carp. Techniques such as gynogenesis, hybrid breeding, and polyploid breeding have been employed to create new varieties with desirable traits. In addition, in-depth studies of grass carp morphology, cytogenetics, and molecular genetics have provided valuable insights into the genetic diversity of this species, facilitating targeted breeding programs.
Study Findings
Key findings include:
- Origin and Geography of Grass Carp: This fish has been bred in China for over 1,700 years and is commonly known as “wan” or “wanyu.”
- Distribution of Grass Carp Germplasm Resources: Ctenopharyngodon idella was originally distributed in China, Russia, and Bulgaria. In China, it primarily inhabits the Yangtze River, Pearl River, and Heilongjiang River. Grass carp has been introduced to 93 countries, with some countries importing it directly from China, India, Hungary, and the United States, among others. Malaysia was one of the first countries to import grass carp from China in the 1980s.
- Genetic Improvement Technology: Grass carp genetic improvement technology focuses on three main areas:
Studies on Grass Carp Gynogenesis: Common grass carp is prone to enteritis, gill rot, and hemorrhagic diseases. Gynogenetic grass carp was improved using gynogenesis techniques, and a large number of improved grass carp were obtained through backcrossing gynogenetic grass carp with common grass carp. The improved grass carp exhibits excellent characteristics such as strong disease resistance, rapid growth rate, strong vitality, and uniform size.
Studies on Hybrid Breeding of Grass Carp: Hybrid breeding has played an important role in improving hybrid varieties and cultivating new varieties in aquaculture. To improve disease resistance in grass carp and cultivate new hybrid grass carp varieties, Chinese aquaculture researchers have conducted numerous artificial hybrid breeding experiments using grass carp as a parent, including intergeneric and intersubfamily hybridization.
Studies on Polyploid Breeding of Grass Carp: Currently, the main technical means for grass carp are gynogenesis and hybridization technology, with a small amount of polyploid breeding. For example, grass carp fertilized eggs induced with heat shock treatment produced a modest proportion of triploid grass carp.
- Application and Conservation Measures for Grass Carp Germplasm Resources: There are two types of grass carp germplasm resources: native Chinese grass carp and Russian golden grass carp. The collection, identification, and preservation of grass carp germplasm provide a solid foundation for the cultivation of new species.
Safeguarding Grass Carp Germplasm for the Future
Protecting grass carp germplasm requires a multifaceted approach. This includes establishing germplasm banks, developing cryopreservation techniques, and implementing strict biosecurity measures to prevent genetic contamination. Additionally, there is a growing need for comprehensive genetic characterization and evaluation of existing germplasm resources to identify valuable traits and maximize their utilization.
Conclusion
The conservation and utilization of grass carp germplasm are imperative for the long-term sustainability of the aquaculture industry. By investing in research, developing innovative breeding technologies, and implementing robust conservation strategies, we can ensure a future where grass carp continues to provide a valuable source of food and livelihood for future generations.
The study has been funded by the National Key Research and Development Program of China, the Special Funds for the Construction of Innovative Provinces in Hunan Province, the National Natural Science Foundation of China, and the China Agriculture Research System of MOF and MARA.
Contact
Shaojun Liu
State Key Laboratory of Developmental Biology of Freshwater Fish, Engineering Research Center of Polyploid Fish Reproduction and Breeding of the State Education Ministry, College of Life Sciences, Hunan Normal University, Changsha, China
Email: lsj@hunnu.edu.cn
Reference (open access)
Wang, Y., Liu, W., Li, Z., Qiu, B., Li, J., Geng, G., Hu, B., Liao, A., Cai, Y., Wen, M., Wang, S., Qin, Q., Luo, K., & Liu, S. (2024). Improvement and application of genetic resources of grass carp (Ctenopharyngodon idella). Reproduction and Breeding, 4(3), 126-133. https://doi.org/10.1016/j.repbre.2024.04.003
