Genotypic Variation and Genotypic Correlations for Sugars and Organic Acids of Strawberries

Genotypic variances and genotypic correlations were estimated for soluble solids content (SSC), titratable acids, and their major constituents, using strawberry genotypes ( Fragaria × ananassa ) not previously selected for flavor or other commercial traits. Genotypic variances estimated for SSC and total sugars were nonsignificant, whereas those estimated for acids were significant and large. Relative expression of acids was stable throughout the season; large genetic × harvest date interactions reduced genotypic consistency for SSC. Despite the absence of detectable genotypic variation for SSC and total sugars, significant genotypic variation was detected for sucrose, glucose, and fructose, and the relative expression of these sugars was stable over harvest dates. The total allocation of sugar to fruit appears fixed, but the distribution pattern among sugar constituents at commercial ripeness is variable. This interpretation was supported by the observation of a strong negative genotypic correlation between sucrose and its components, glucose and fructose. These results suggest that opportunity exists for genetic improvement of acids, but that selection response for SSC will be difficult to obtain.