Abstract: The NEW GIFT Nile tilapia (
Oreochromis niloticus niloticus
L.) is a nationally certificated new strain
selected over 14 years and 9 generations from the base strain of GIFT Nile tilapia, introduced in 1994. This new variety
has been extended in most of areas of China. The management of genetically improved strains, including the genetic
markers for identification is needed urgently. RAPD analysis was conducted and their conversion to SCAR markers was
developed. From NEW GIFT Nile tilapia, two strain-specific RAPD bands, S
304624 bp and S
36568 bp were identified. The
strain-specific RAPD bands were gel-purified, cloned, and sequenced. Locus-specific primers were then designed to
amplify the strain-specific bands. PCR amplification was conducted to test the variations in allele frequencies of two
converted SCAR markers among the NEW GIFT Nile tilapia and its base strains, as well as 7 additional farmed strains
worldwide. The frequency of SCAR marker I (553 bp) was 85.7% in NEW GIFT Nile tilapia, but 16.7% in the base strain.
The frequency of SCAR marker II (558 bp) was 91.4% in NEW GIFT Nile tilapia, but 0% − 70% in the 7 other strains. In
order to confirm the utility of these two markers, an examination was conducted for a wild population from Egypt,
resulted the frequency of SCAR I and II was 10% and 70%, respectively, much lower than that of New GIFT strain. The
increase in allele frequency of these two SCAR markers suggests that these markers might be genetically linked to the
quantitative trait loci (QTL) underlining the performance traits by long term selection, and indicate the bright potential of
SCAR marker technology for tracking generations during selection progress and for distinguishing among genetically
improved strain and other strains.
