Breeding methods and selection theory.
1984
Gallais A.
A comprehensive strategy of varietal development appears to be with two main axes: population improvement by recurrent selection and varietal development. The aim of population improvement must be to improve the varietal ability of the population(s), i.e., the expected value of all varieties of a given type which can be derived from the populations(s). The aim of varietal development will be to extract the best possible varieties from a given generation of the breeding population(s). So it is clear that the system of testing in population improvement must be adapted to the type of variety. To develop hybrids the combining ability has to be improved, for synthetics the synthesising ability and for line development the line value of the material. To develop clones it is only necessary to improve the value "per se" of the breeding material. One of the main problem to solve is to have good predictors of the varietal ability of offspring (in crossing) of a given individual. In this stragegy pedigree method for line or hybrid development could be considered as a method of varietal development. Formulae for genetic advance in population improvement and varietal development can be given in terms of genetic effects for varietal abilities of one or of several genotypes. In the absence of epistasis only additive genetic effects for varietal ability contributes to population improvement. Such formulae allow the optimisation and comparison of the breeding methods.
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