Applications of Microsatellite Markers to Genetic Management of Carps in Aquaculture

ALMAS A GHEYAS PhD THESIS, INSTITUTE OF AQUACULTURE ii ABSTRACT Carp aquaculture in South Asia suffers severely from a lack of genetic management, which has eroded the genetic quality of both captive and wild populations. Use of molecular markers, especially microsatellites, has revolutionized genetic management of hatchery stocks through its ability to detect kinship between individuals and hence in controlling level of inbreeding and loss of genetic diversity. In the present PhD work, microsatellite markers were applied to breeding programmes for silver carp (Hypophthalmichthys molitrix) and common carp (Cyprinus carpio) to study different genetic management aspects and new markers were generated from rohu (Labeo rohita). A set of newly isolated microsatellite markers from silver carp were characterized and two pentaplex PCR reactions were optimized to enable rapid genotyping of large number of individuals at 10 microsatellite loci. The utility of these markers in parentage, sibship and relatedness analysis were assessed by applying them to groups of fish with known relationship. These markers were used for parentage analysis in a breeding programme designed to estimate heritability of harvest weight and length in silver carp. Fulland half-sib families were created in three sets of partly factorial mating and all the families from each set were reared in communal ponds from very early life stages. With ten microsatellites 96.3% of the offspring could be assigned to a single family. Heritability estimates were found to be 0.65 ± 0.13 for weight and 0.50 ± 0.13 for length. High estimates of h suggested that this population should respond rapidly to selection for increased harvest size. Microsatellite markers were also applied to monitor the early stages of a mass selection programme in common carp (Cyprinus carpio). The selection was initiated from a base