MICROSATELLITES POLYMORPHISM ASSOCIATED WITH HEPCIDIN/HAMP GENES POTENTIAL FOR SELECTIVE BREEDING OF DISEASE-RESISTANT BY Streptococcus agalactiae IN NILE TILAPIA IN VIETNAM

Abstract

Streptococcosis is considered an infectious disease causing significant economic loss in tilapia aquaculture in the world. Fish hepcidin is known as a hepatic antimicrobial peptide (HAMP), and is associated with innate immunity, which defends against various bacterial infections and viruses. Sixty Phu Ninh tilapia after the challenge test with Streptococcus agalactia at a dose of 2,2x10⁶ cfu/ml were sampled to analyse microsatellite/SSRs polymorphism in the hepcidin/HAMP genes and the resistance to S. agalactia. This study examined the relationship between seventeen microsatellite/SSRs polymorphism in the hepcidin/HAMP genes and the resistance to S.agalactia in the Phu Ninh tilapia strain. The results indicated that 13/17 hepcidin/HAMP-related SSRs were polymorphic markers based on the number of alleles, effective alleles, observed heterozygosity, expected heterozygosity, polymorphism information content, and Hardy-Weinberg equilibrium. In this study, there was a significant difference in genotype and allele frequency between two groups (alive fish and dead fish after challenging with S. agalactiae) for four SSRs (SSR3, SSR5, SSR14, and SSR16) (P < 0.05).  . These four SSRs are utilized as marker-assisted selection (MAS) in the breeding of tilapia for S. agalactiae resistance.