APPLICATION OF THE CONCEPTS OF TEST VALUE AND VARIETAL VALUE TO THE STUDY OF GENETIC ADVANCE IN RECURRENT SELECTION - A SYNTHESIS

The concepts of varietal ability and value in test of a genotype or group of genotypes are specified according to the type of variety (clones, hybrids, lines, synthetics) and the testing system (phenotype, S1, General combining ability (GCA), line value, General synthesizing ability (GSA)). Varietal ability and value in test are to be considered as any quantitative characters for which it is possible to define additive effects, dominance effects and epistasis. For diploids in recurrent selection, only additive effects and additive× additive epistasis for varietal value contribute to genetic advance. Genetic advance depends on the covariance between the testing value of the parents and the test value of the progeny by intercrossing. Such a parent-offspring covariance is, in the absence of epistasis and inbreeding, one half of the covariance between additive effects in test of the parents and additive effects in test of their progenies. This allows one to express directly the genetic advance in varietal value according to the type of variety and to the testing system used in recurrent selection. The case of biallelic populations is considered; it allows some discussions on the relative values of components of variance of varietal and test values. © 1990 Kluwer Academic Publishers.