Microsatellite genotyping of contributing broodstock and selected offspring of Haliotis midae submitted to a growth performance recording scheme

[摘要] ENGLISH ABSTRACT: The indigenous abalone Haliotis midae is one of the most remarkable and highly exploited speciesof marine molluscs in South Africa. It is the only species of southern African Haliotidae to becommercially reared and has been successfully cultured for almost two decades. Its short history ofdomestication along with market demands and the need to develop efficiency in the productionprocess has resulted in an increased interest in the possible genetic improvement of this species.The unhurried growth rate associated with H. midae is a cause of particular concern to the industry,predominantly with regards to profitability and competitiveness in the market place. A modestamount of work has so far been directed at establishing a means of enhancement for selectivebreeding on the commercial level. Genetics plays a key role in the establishment of successfulimprovement programmes in various aquaculture species. The aim of this study was to developspecies-specific microsatellite markers for the abalone and subsequently perform parentageassignment on farm produced animals entered into a growth performance recording scheme.Animals were obtained from the hatcheries of three commercial abalone farms situated in theWalker Bay region in the Western Cape.Microsatellites were isolated using the enrichment-based FIASCO method, and characterised intoperfect, imperfect and compound repeats according to the structural nature of their repetitive units.From the partial gDNA libraries obtained and 365 screened colonies, a total of 54 loci were located.PCR primers were designed for 36 markers and the 15 primer pairs that displayed loci with thehighest level of polymorphism were subsequently chosen for fluorescent labelling. The markerswere tested on a subset of 32 wild H. midae individuals to determine their usefulness and efficiencyin genotyping. Five markers, along with five others that were previously designed, were chosen forassigning parentage to the animals submitted to the performance recording scheme. Three thousandoffspring from each of the three participating farms were equally divided and reared at five differentlocations. From each location 20 fast growing and 20 slow growing juveniles, as well as thebroodstocks, were sampled and genotyped using the ten chosen microsatellite loci. Two farms had60% of offspring unambiguously assigned to a single parental couple. Assignments showedpatterns of dominant male and female brooders, but no trend in brooders specifically contributing tofast or slow growing offspring. Parentage assignment for the third farm was, however, unsuccessfuldue to lack of broodstock data. In future, screening of all available broodstock will ensureacquisition of relevant pedigree information. The results obtained in this study are an initial step inthe development of a genetic improvement programme for commercial Haliotis midae.

[发布机构] Stellenbosch University