4 - Central Institute of Brackishwater Aquaculture

Natlonal Workshop-cum-Tralning on Bioinformatlcs and Informatlon Management in Aquacultura
Where 11F= Rate of inbreeding per generation
N,= Effective population size
N, = Number of female brood fishes used for seed production
N,= Number of male brood fishes used for seed production
So to improve the genetic status of any population, hatchery managers should
decrease inbreeding rate and increase effective population size. Selective
breeding plays vital role to improve genetic status of fish in a positive direction
which has already been demonstrated in case of Salmon at Norway, Tilapia at
Philippines and Rohu at CIFA, India.
Objectives of selective breeding
Objectives of a selective breeding programme is to change the average
performance of the targeted trait i.e. growth rate, disease resistance, better flesh
quality, feed conversion efficiency etc. of the population in a favorable direction.
3. Estimation of phenotypic and genetic parameters
Estimation of phenotypic and genetic parameters is essential in the design of
genetic improvement programs. They include phenotypic and genetic variances
and covariances and their linear functions such as heritability and phenotypic and
genetic correlations. They enable the prediction of genetic gain and of correlated
responses in genetic improvement program.
Selection is an age-old process in nature. Fittest organism survives and other
eliminated. Selection also can be achieved artificially. In this process best
individuals are selected as parents so that parents pass on their superior genes
to their progeny and better progeny can be obtained. Selective breeding based
on principle of quantitative genetics. Which indicated that that phenotype of an
individual, which can be measured or scored, could be partitioned in to two
components. One attributable to the influence of genotype i.e. the particular
assemblage of genes possessed by the individual and other one attributes to the
influence of environment i.e. all non-genetic components.
SoP=G+E
Where P = Phenotype of an individual
G = Genotype
E = Environmental (Non-genetic) component
Quantitative phenotype exhibit continuous variation, the only way to study them
is to analyze the variance that exists in a population. The phenotypic variance
(VP) that is observed for a quantitative trait is the sum of the genetic variance
(VG) and (VE) and the interaction that exists between the genetic and
environmental variance (VG+E). ,
Genetic variance is the component of interest in selective breeding program. VG
is further subdivided in to three component i.e. additive genetic variance (VA),
dominance genetic variance (VD) and the epistatic genetic variance (VI).
VG = VA+ VD +VI