Genetic Variation and Response to Selection for Early Season Fruit Production in California Strawberry Seedling (Fragaria ×ananassa Duch.) Populations

Abstract

The genetic opportunity for selection of early fruiting strawberry cultivars was evaluated using seedling populations from the Univ. of California (UC) breeding program in three years. Narrow-sense heritabilities for early season yield and for the proportion of an individual's total yield expressed early were moderate (h2 = 0.24-0.53) and broad-sense heritabilities were slightly larger (H2 = 0.31-0.70), suggesting the presence of some nonadditive genetic variance for these traits. These two traits were genetically correlated with each other (rg = 0.78-0.98), but only early yield was consistently genetically correlated with seasonal yield (rg = 0.52-0.82). Selection was performed for each trait using an index on full-sib family means and individual phenotypic values in two of the three years, and predicted response was compared with that obtained using vegetatively propagated runner plants from selected genotypes in the subsequent fruiting season. Statistically significant (P < 0.05) selection response was obtained in one of two years for each trait, and combined analysis demonstrated highly significant (P < 0.01) response for both traits. However, realized response over all traits and years was just 27.3% of that predicted based on the estimated heritabilities and applied selection intensities. These results suggest that selection for early yield should be based at least in part on runner plant evaluations rather than exclusively on seedling performance.