Combining ability analysis for yield and quality traits in tomato hybrids

Abstract:

Leading tomato geneticists have long argued that combining ability estimates are the most reliable predictors of hybrid performance, yet few diallel analyses have been published for the landrace-rich germplasm of southern Mexico. This research analysed general combining ability (GCA) and specific combining ability (SCA) for yield and quality traits in a 6 × 6 half-diallel cross among six diverse tomato parents evaluated at the Instituto de Ciencias Agrícolas de Oaxaca, Mexico, during two growing seasons (2022 and 2023). Fifteen F₁ hybrids and their parents were grown in a randomised complete block design with three replications. Traits recorded included fruit yield per plant, average fruit weight, total soluble solids, titratable acidity, lycopene content and number of locules. Both GCA and SCA variances were significant (P<0.01) for all traits, with the GCA:SCA ratio exceeding 2.0 for yield and fruit weight, indicating predominantly additive gene action. Parent P1 (a local Oaxacan landrace) had the highest positive GCA for yield (1.51), while P6 topped GCA for TSS (0.83). The cross P1 × P6 recorded the best SCA for yield (1.51) and the highest standard heterosis (42.7%). Fruit yield in P1 × P6 reached 4.63 kg plant⁻¹, exceeding the best parent by 28.3%. These findings identify P1 and P6 as priority parents for hybrid tomato breeding programmes targeting both yield and eating quality in subtropical Mexican environments.