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Parental potential, or breeding value, was evaluated for strawberry (Fragaria × ananassa Duch.) genotypes selected for high, intermediate, or low phenotypic expression of soluble solids content (SSC) and titratable acid content (TA). Progeny means and genetic variance parameters were estimated using seedlings from 40 crosses among these selections, conducted in two factorial sets. Selection response for breeding value was detected for SSC in the upward direction and for TA in both upward and downward directions. Populations created by divergent selection of parents followed by intermating expressed additive genetic variances 2.3 and 9.3 times larger than those estimated for ap- propriate controls for SSC and TA, respectively. For TA, the response to selection for breeding value was consistent with results for genotypic selection reported earlier. The significant selection response in breeding value obtained for SSC differed from the results of previous clonal tests that had detected no significant genotypic selection response. These results, together with previous assessments, suggest that cumulative genetic gain can be obtained for both SSC and TA. However, gain for SSC will be contingent on selection under conditions that approximate commercial treatment; this will not be necessary for TA, as expression for this trait is stable across test location and cultural treatments. Strawberry flavor is conditioned in part by the balance be- tween SSC and TA expressed in ripe fruit (Sweeney et al., 1970). Genetic variation for SSC and TA in strawberry can be exploited by selection and propagation of 'specific genotypes and by choice of appropriate' parents and control of cross combi- nations. When genetic effects are large and mostly additive, both genotypic values and breeding values are predictable from the performance of individual seedling phenotypes. However, if dominance effects are large, the correspondence between gen- otypic value and breeding value will be low and clonal perform- ance may be a poor predictor of parental value. The effectiveness of mass selection in detecting superior parents and genotypes for SSC and TA depends on the mode of inheritance for genes that condition these traits. The study reported here is the third "in a series aimed at un- derstanding the inheritance of SSC and TA in strawberries and deriving selection strategies for developing cultivars with im- proved flavor. Broad-sense heritabilities (H*) and narrow-sense heritabilities (h*) were estimated in an earlier study, using seed- lings from controlled crosses among genotypes representative of current advanced-generation germplasm (Shaw et aI., 1987). Results from this initial genetic survey demonstrated large dom- inance effects for SSC (h 2

Response to Selection and Associated Changes in Genetic Variance for Soluble Solids and Titratable Acids Contents in Strawberries