SUMMARY
Tomato (Solanum lycopersicum L.) is one of the most important vegetable crops grown in Nigeria, either for fresh market or industrial purposes, necessitating the development of a robust tomato breeding programme aimed at maximizing genetic improvement on economically important traits. In this study, the combining ability, nature of gene action, heterosis, and heritability for morphological, nutritional, and physicochemical parameters of tomato were examined in five tomato parents and ten F1 offsprings, generated with a 5 × 5 half diallel mating design in the greenhouse in 2017. The field evaluation was conducted at the Teaching and Research Farm of Ladoke Akintola University of Technology, Ogbomoso, Nigeria during the cropping season of 2018 using a randomized complete block design with three replications. Analysis of variance for combing ability revealed that both additive and nonadditive gene actions contributed to the fundamental genetic mechanism underlying the inheritance of the measured traits. The top two general combiner parents were UC-OP and Ib-local. Furthermore, the best tomato hybrid specific combiners were FDT4 × UC-OP, FDT2 × Ib-local and UC-OP × Ib-local which involved one parent having a high general combining ability effect for fruit yield and the other having other desirable traits. These hybrids may be further utilized in tomato breeding programmes.