BASIC FEATURES OF BREEDING

1. BASIC FEATURES OF BREEDING Taryono Faculty of Agriculture Gadjah Mada University

2. Introduction • Breeding objectives and strategies are 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

3. 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

4. Objectives and decisions • 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

5. Breeding Pattern • Local adaptation • Genetic base • Recombination • Selection • Population • Trial and Multiplication • Genetic conservation

6. Local adaptation • Fishes are out-breeders • They have various morphogenetic mechanism that vapor crossing, tend to carry deleterious recessives in the heterozygous state and show inbreeding depression

7. Local adaptation • 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

8. Genetic base • 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: • Locally successful strains • Strains which appear to offer local adaptation or at least specific desired characteristics • The product of operations specifically designed to widen the genetic base

9. Recombination • 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)

10. Selection • It is 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

11. Selection methods and their genetic base • 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

12. Population • Fishes are outbreeder 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 • Open pollinated populations (synthetic) • Hybrid It is constructed by crossing more or less inbreed lines of outbreeders organism

13. Trials and multiplication • 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

14. Genetic conservation • 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 building and maintaining collection of fishes as a living stocks