The impact of differential success of somatic embryogenesis on the outcome of clonal forestry programs. I. Initial comparison under multitrait selection

A breeding program where clones or clone mixtures are deployed through somatic embryogenesis of superior genotypes produced from elite-parent crosses was evaluated by simulation. A recurrent-selection scheme for general combining ability was considered with a breeding population size of 100 individuals. The population was assortatively pair-crossed with offspring cloned in a progeny test to facilitate forward selection of the next generation. Apart from crosses for the population advancement, elite crosses were made among 10 top-ranking individuals in each generation. These crosses differed in their propensity to produce somatic embryos (defined as induction success rate); the impact of this variable propensity on genetic response for two traits in selected 10-clone deployment mixtures was evaluated. The two traits considered in this study can be regarded as productivity and quality. The results revealed that variation in success of clonal propagation does not necessarily lead to a reduction in potential genetic gains from selected clonal mixtures. This can be explained by the relatively small variation that exists among elite crosses, as opposed to large within-family variation. This large within-family variation provides ample potential for selecting superior offspring genotypes, even though they may have not originated from crosses among the very best of the elite parents. This conclusion holds for a range of heritability, correlations between traits, and their relative economic importance.