Download basic features of breeding

FISH GENETICS
AND BREEDING
Taryono
Faculty of Agriculture
Gadjah Mada University
Why do we need to study fish
genetics and breeding?
Aquaculture
The cultivation of aquatic
animals, such as fish and
aquatic plants for recreational
or commercial purposes
The Economics of Aquaculture
Worldwide demand for
aquaculture products is
expected to grow by 70%
during the next 30 years
If demand continues to rise
and wild catches continue to
decline
 We will see a deficit of
consumable fish
Aquaculture together with
better resource management
practices will in part
overcome this problem
Objectives management
in aquaculture
 Improving production yield
by selecting for larger or
heavier animals
 Improving growth rates (get
to market size faster)
 Production of sterile or
monosex populations
 Maximizing post-stocking
survival in natural water
bodies (fisheries
management)
Breeding
Activity
What is breeding?
The production of plants and animals especially for the
purpose of developing new or better types
The propagation and genetic modification of organisms
for the purpose of selecting improved offspring
The Application of several techniques of hybridization
and selection
The application of genetics
Breeding objectives and
strategies
Must be defined on the basis of secure scientific
knowledge of :
1. the agriculture and the society that are to be served
2. Essential genetic features of the organism
Breeder is an applied evolutionist working
toward defined objectives by tolerable well
understood methods
Subject should be set up in a simple manner
Objectives and decisions
Every breeding program must have well defined
objectives which are both economically and biologically
reasonable
Economic criteria are important, even if not stated in
strictly monetary terms, because the breeder must be
assured that we are trying to produce strains that the
users will actually want.
The biological objectives are determined by scientific
knowledge and general “feel” of the organism (yield
and quality)
Objectives are the first of the breeders decisions
Objectives and decisions
a.
b.
c.
d.
Breeders will have to decide:
What parents to include and why
What pattern of crossing and passage through
the generation to adopt
What methods of selection to use
How we will decide upon the ultimate release
or discard of the product
Breeding Steps
Deciding breeding objectives
Development of breeding materials
Selection
Lines evaluation
Released
Multiplication
Important term
Local adaptation
Genetic base
Recombination
Selection
Population
Trial and Multiplication
Genetic conservation
Local adaptation
The process of changes of an individual’s structure, morphology,
and function that makes it better suited to survive in a given
environment
 Organisms are geographically differentiated into locally
adapted strains
 Breeder is concerned with the performance in one
environment or a limited group of similar environment
because no one strain ever excels over the entire range
of any widespread environment
 Breeder can do to promote local adaptation in one or a
few similar environment
Genetic base
The genetic variability of characteristics which is available for
breeding works
 The genetic variability available always greatly
exceeds what breeder can effectively handle
 Breeder must work with parental materials
which is more or less locally adapted, include:
a) Locally successful strains
b) Strains which appear to offer local adaptation or at least
specific desired characteristics
c) The product of operations specifically designed to widen the
genetic base
Recombination
The process whereby new combination of parental characteristics
may arise in the progeny, caused by exchange of genetic material of
different parental lines
 Enhanced adaptation normally follows from selection and
isolation of new strains which are better adapted than their
parents
 Recombination is therefore a crucial phase of any breeding
program
 Breeder set up crosses in order to generate recombination which
probably will be transgressive with respect to a better parent
 The amount of recombination in one breeding cycle will depend
upon several genetic factors (parent relationship, breeding system
and population size)
Selection
The process determining the relative share allotted individuals
of different genotypes in the propagation of a population
 The oldest methods for improvement
 Breeder chooses what to keep and what to throw away
 The method allows improved, more homogenous strains for instance
with better yield and quality
 Selection must be done as quick and simple as possible using a special
characteristic which is correlated to yield or quality
 When selection is used as a breeding procedures, one can select and
accumulate only what is available in the current population
 No matter what method is used in breeding, it inevitably involves
selection which is the most difficult part of the overall breeding process
 Heritability should be used as a consideration in choosing correlated
characteristics
Selection methods
The most common breeding procedure was mass-selection which in
turn was subdivided into negative and positive
 Negative selection
The most primitive and least widely used method which can lead to
improvement only in exceptional cases
implies culling out of all poorly developed and less productive
individuals in a population whose productivity is to be genetically
improved
The remaining best individuals are propagated as much as necessary
 Positive selection
Only individuals with characters satisfying the breeders are selected from
population to be used as parents of the next generation
seed from selected individuals are mixed, then progenies are grown
together
Population
A community of individuals which share a common
characteristics


Fishes are out-breeder organisms:
They have various morphogenetic mechanisms that favor
crossing, tend to carry deleterious recessives in the
heterozygous state and show inbreeding depression
Two basic populations:
1. Open pollinated populations (synthetic)
2. Hybrid
It is constructed by crossing more or less inbreed lines of outbreeders organism
Trials and multiplication
An inquiry in which an investigator chooses the levels
(values) of input or independent variables and observes
the values of the output or dependent variable(s).
 The decision system whereby a new strain goes
forward from the breeder to user is essentially a
hierarchy of trials intended to predict its performance
 The decision to exploit a new strain agriculturally is
accompanied by a decision to multiply it so that the
materials shall be commercially available
 The key points of multiplication are purity, cleanliness
and health of stocks
Genetic conservation
Maintenance of genetic resource
 Long term progress in breeding depends upon provision of an
adequate store of genetic variability in the form of diverse
parents for inclusion in the genetic base of breeding program
 Genetic variability tends to decline and yield to narrow genetic
base, apparent in slow breeding progress or pathological crises
 It is now universally accepted that the decay of variability in
actual agriculture is so rapid that the future genetic base must
be safeguarded by a great international program of genetic
conservation
 There is no feasible alternative to build and maintain
collection of fishes as a living stocks
Fish Breeding
Selective breeding
The choosing of individuals of a single strain and
spp.
Recombination Breeding
Hybridization breeding
The mating of unrelated strains of the same spp.
to avoid inbreeding
Crossbreeding
The crossing of different spp.