Integrating combining ability and multivariate analysis for the selection of superior tomato hybrids

Tomato is a globally important crop and the second most consumed vegetable worldwide, with an estimated global production of 188 million tons annually. However, high-yield production systems increase vulnerability to pests and diseases, posing major challenges for tomato breeding programs. This study aimed to evaluate combining ability and identify superior Italian-type tomato hybrids by integrating a North Carolina II (NCII) mating design with multi-trait selection using the multi-trait genotype-ideotype distance index (MGIDI).

Nine inbred lines previously characterized for resistance alleles were crossed in a 4 × 5 factorial scheme, generating 20 hybrids, which were evaluated together with their parents and a commercial check in a randomized complete block design with three replications. Traits related to plant architecture, yield, and fruit quality were assessed.

Combining ability analysis based on the NCII design revealed significant effects of specific combining ability (SCA) (p < 0.01) for most plant architecture traits and for productivity per plant (PP), with SCA mean squares exceeding those of general combining ability (GCA) for key traits, indicating the predominance of non-additive genetic effects. By contrast, internode diameter (ID) and fruit size (FS) showed stronger additive contributions, with broad-sense heritability estimates of 60.42% and 82.95%, respectively. In the hybrid evaluation, all plant architecture traits showed significant genotypic effects (p < 0.01), with heritability ranging from 64.29% to 85.85%. Yield-related traits were also highly significant (p < 0.01), with heritability values ranging from 67.75% to 87.03%, and several hybrid combinations outperformed the commercial check for yield per plant. The MGIDI analysis retained three factors (eigenvalues > 1), explaining a substantial proportion of the total variation, and identified hybrids H17, H2, and H11 as the closest to the ideotype, combining favorable plant architecture, fruit quality, and yield. Overall, these results highlight the breeding potential of the evaluated inbred lines and indicate the need to validate the selected hybrids in multienvironment trials prior to recommendation.