Specific combining ability is tested for development of

Specific combining ability is tested for the development of Synthetics.
Specific combining ability (SCA) is the relative performance of a cross that is associated with non-additive gene action, predominantly contributed by dominance, epistasis, or genotype-environment interaction effects, and is directly related to the breeding value of a parent.
A synthetic variety is developed by intercrossing several genotypes of known superior combining ability i.e., genotypes that are known to give superior hybrid performance when crossed in all combinations.