Genetic characteristics of broodstock and offspring of the seven-band grouper (Hyporthodus septemfasciatus) using fluorescent-AFLP markers

Abstract

Seven-band grouper (Hyporthodus septemfasciatus) is a commercial rocky reef fish in East Asia that has been regarded as a promising species for aquaculture. To investigate the broodstock contributions to offspring for the sustainability of fry production, 62 individuals ofH. septemfasciatusfrom two broodstocks and one offspring population were analysed using fluorescent-AFLP. A total of 602 bands were amplified and 70.10% of them were polymorphic. The numbers of polymorphic loci were 308 (Pbroodstock I= 55.50%) and 356 (Pbroodstock II= 63.12%) in the two broodstocks, and 294 (Poffspring= 52.88%) in the offspring, respectively. The average values of Shannon diversity index (I) and expected heterozygosity (H) were higher in the broodstock (Ibroodstock I= 0.281,Ibroodstock II= 0.244,Hbroodstock I= 0.185,Hbroodstock II= 0.161) than those in the offspring (Ioffspring= 0.243,Hoffspring= 0.161). AMOVA and FSTanalyses showed that significant genetic differentiation between broodstock and offspring populations, and limited effective broodstock population size has contributed to the offspring. Both STRUCTURE and Principal Coordinates Analysis (PCoA) also showed the three populations composed of two stocks and most offspring individuals (95.0%) only originated from 44.0% of the individuals of broodstock I, which may have negative effects on sustainable fry production. Therefore, genetic variation between broodstock and offspring should be monitored, and large effective size of broodstock should be employed to ensure the success of commercial breeding programmes. Our data provide a useful genetic basis for future planning of sustainable culture and management ofH. septemfasciatus.