DIFFERENTIATION OF TWO CLARIAS SPECIES (Clarias macrocephalus AND C. gariepinus) AND THEIR HYBRIDS BASED ON PCR-RFLP ANALYSIS

Abstract

      Catfish hybrids (Clarias macrocephalus x C. gariepinus) have been popularly cultured in Viet Nam and have possibly escaped to the wild. Identification of hybrid individuals has become important in fishery resource management and aquaculture, but hybrid differentiation based on morphology is highly uncertain. This study employed PCR-RFLP method using a mitochondrial (cytochrome C oxidase subunit I, COI) marker and a nuclear (rhodopsin, rho) marker to differentiate hybrids from the parental species. Two genes were sequenced from 12

samples of two species (6 of each species) and 3 samples of the culutred hybrid. Sequences of the two species were aligned to find species-specific restriction enzymes. Restriction enzymes of SpeI and XcmI were selected to digest at species-specific sites of COI and rho genes, respectively. Results confirmed that C. macrocephalus is maternal lineage of the cultured hybrid. Sequence chromatogram and fragments after XcmI digestion of rho gene of the hybrid revealed intermediate patterns between two parental species. Therefore, PCR-RFLP analysis of COI and rho genes is an effective and accurate method for identification of catfish hybrid individuals.