Heritability and Genetic Diversity of Important Traits in Tomato (Solanum lycopersicum) Population Derived from 'Brenta' Cultivar

Introduction: Tomato (Solanum lycopersicum L.) is one of the most important vegetable crops worldwide. Although the hybrid cultivar Brenta is widely cultivated because of its desirable agronomic performance, limited information is available regarding the inheritance of quantitative traits and the extent of inbreeding depression in its F₂ generation. The objective of this study was to estimate genetic parameters of important quantitative traits, evaluate genetic variability, determine broad-sense heritability and expected genetic advance, quantify inbreeding depression in the F₂ generation of the hybrid tomato cultivar Brenta, and identify effective selection criteria for improving fruit yield.
Materials and Methods: The experiment was conducted under greenhouse conditions using 100 F₁ plants and 1,000 F₂ plants of the commercial hybrid tomato cultivar Brenta. Fruit length, fruit diameter, fruit firmness, fruit uniformity, fruit size, number of fruits per plant, plant height, and fruit yield were evaluated using standard horticultural procedures. Genetic analyses included estimation of genotypic and phenotypic variances, genotypic and phenotypic coefficients of variation (GCV and PCV), broad-sense heritability (H²), expected genetic advance, and inbreeding depression. Pearson correlation coefficients were calculated to evaluate relationships among the studied traits.
Results: Considerable genetic variation was observed among F₂ individuals for most traits, indicating sufficient variability for selection. Phenotypic variation generally exceeded genotypic variation, suggesting a moderate environmental influence on trait expression. Among the evaluated traits, the number of fruits per plant exhibited the highest genotypic coefficient of variation (33%) and high broad-sense heritability (70%), indicating that this trait is largely controlled by genetic factors and can be effectively improved through phenotypic selection. In contrast, fruit size showed the lowest heritability (27%), suggesting limited selection efficiency. Fruit yield in the F₂ generation decreased by approximately 9.91% compared with the F₁ generation, confirming the occurrence of inbreeding depression. This reduction was mainly associated with a decline in the number of fruits per plant rather than fruit size. In addition, fruit firmness and fruit uniformity decreased noticeably, indicating that inbreeding adversely affected both yield and fruit marketability. Correlation analysis revealed significant positive relationships between fruit yield and the number of fruits per plant, fruit size, fruit length, fruit diameter, and plant height. Conversely, fruit firmness showed a weak negative correlation with yield, suggesting that simultaneous improvement of productivity and fruit quality requires balanced selection strategies.
Conclusion: The results demonstrated that the F₂ population of the hybrid cultivar Brenta possesses substantial genetic variability for most quantitative traits, providing valuable opportunities for selection in breeding programs. Among all evaluated traits, the number of fruits per plant proved to be the most reliable selection criterion because of its high genetic variability, high broad-sense heritability, considerable expected genetic advance, and strong positive association with fruit yield. The observed reductions in fruit yield, firmness, and uniformity clearly indicate the detrimental effects of inbreeding depression following self-pollination of F₁ hybrids. Therefore, the reuse of F₂ seeds for commercial production is not recommended, as it may lead to considerable losses in both productivity and fruit quality. The genetic information generated in this study provides a useful basis for tomato breeding programs aimed at improving yield while maintaining desirable fruit quality traits. Future studies incorporating larger segregating populations, multi-environment evaluations, and molecular marker-assisted selection are recommended to further improve breeding efficiency and accelerate the development of superior tomato cultivars.