Abstract
Exp. 1. Frequency distributions of strawberry seedlings for firmness and skin toughness of fruit were unimodality, exhibiting a normal distribution curve. These two traits seemed to be polygenitically inherited. A highly significant correlation (0.93∿0.98) was found between firmness and skin toughness. The heritability was estimated by : 1) comparing variances between seedlings and those of the parents, 2) computing the parent-offspring regression, and 3) analyzing the variance between the female and male factors. Broad-sense heritabilities for the firmness were 0.67, 0.90, and 0.51 ; those for the skin toughness were 0.59, 0.73, and 0.28. A highly additive genetic effect was observed but the dominance effect was small according to the analysis of variance between female and male factors ; hence, the difference between broad-sense and narrow-sense heritability was small. Exp. 2. The heritability estimated by the selection response to F2 from F1 was 0.43, and approximated values obtained by the comparison between the variance of the seedling population and that of the parents and by the analysis of variance between female and male factors. In conclusion, these two methods were more suitable than that of the parent-offspring regression for predicting heritability by the selection response. A relatively high heritability was found in the fruit firmness by any statistical method. Therefore, the implementation of clonal selection based on several generations may be more effective than that on the F1 generation. A superior clonal line could be selected from the progenies after the frequency of firm-fruited seedlings has increased and the selections hybridized in the early stages of breeding.
