9781888569551-ch38

Proceedings of the Third World Fisheries Congress: Feeding the World with Fish in the Next Millenium—The Balance between Production and Environment

Genetically Improved Farmed Nile Tilapia and Its New Selected Generation in China

Li Chenhong, Li Si-fa

doi: https://doi.org/10.47886/9781888569551.ch38

A genetically improved strain of tilapia was selectively bred from a combination four Asian (Israel, Singapore, Thailand, and Taiwan) and four African (Egypt, Ghana, Kenya, and Senegal) strains of Nile tilapia Oreochromis niloticus by the International Center for Living Aquatic Resources Management (ICLARM) etc. (Pullin et al. 1991). The growth of four African strains and four Asian strains was compared; no particular strain showed any advantage. So, these eight strains were pooled to found a mixed-base population. Synthetic selection was carried on the base population to obtain a fast-growing “super” strain of farmed Nile tilapia known as GIFT.

The GIFT strain was introduced to China by ICLARM and the Shanghai Fisheries University in 1994. After that, its growth performance was evaluated in China’s three major agro-ecosystems in 1995 and 1996: Qingdao, Yellow River Basin, Shanghai; Huzhou, Yangtze River Basin; and Guangzhou, Pearl River Basin. At the same time, characteristics including morphological, biochemical, and molecular traits; cold and salinity tolerance; and seinability of the GIFT strain were studied and compared with those of main strains cultured in China: Egypt92, Sudan 78, Egypt 88, and America.

The growth rate of the GIFT strain was 5–30% higher than that of Chinese cultured strains in three on-station trials (Li et al. 1998a, 1998b). Its average production per unit area of pond was 20–30% higher than that of Chinese cultured strains in 32 on-farm trials (Li et al. 1997). In brackish water, the growth rate of GIFT was 60–110% higher than that of Chinese cultured strains (Li and Li 1999). Seinability of GIFT was one to two times that of Chinese cultured strains (Li et al. 1999; Li et al., unpublished data). Cold tolerance of GIFT was inferior to that Chinese cultured strains (Li and Li 1996). Overall, GIFT tilapia were proven to be a good strain of tilapia for culture in China; the National Certification Committee of Aquatic Wild and Bred Variation, Department of Agriculture, China, certified GIFT as a good breed.

Biochemical genetic variation of GIFT, Egypt92, Sudan 78, Egypt 88, and America strains of Nile tilapia were analyzed by acrylamide gel electrophoresis (Zhao et al. 1997). The esterase-2 (EST-2) locus was only found in GIFT and Egypt92 strains (Figure 1), possibly because Egypt92 was one ancestor of GIFT. Restriction fragment length polymorphism (RFLP) analysis was conducted for the ND5/6 gene of mitochondrial DNA of GIFT, Egypt92, Sudan 78, and Egypt 88 strains of Nile tilapia (Li et al., unpublished data). Their indices of haplotype diversity and nucleotide diversity were 0.6879 ± 0.0978 and 0.02659 ± 0.0978, respectively, and the range of these strains was Sudan78 > GIFT > Egypt92 > Egypt88. The GIFT line also had several unique haplotypes that probably resulted from its diverse ancestry. The haplotype diversity of Sudan78 was the highest, probably caused by gene introgression from other species of tilapia after a long period of culture in China.

To further improve the growth performance of GIFT, a national research program began in 1996. At the end of 1996, 1,179 GIFT fish were used to found three base populations at three stations: Qingdao National Tilapia Farm, Guangdong National Tilapia Farm, and Bengbu Aquaculture Institute. The project was carried out at three areas to develop lines for each particular regional environment (north, middle, and south) through mass selection.