Genetic Analysis and Combining Ability for Improving Yield and Salt Tolerance in Tomato

The experiment was planted on tomato were conducted at a private farm in Village in Kafr el-Sheikh city, Kafr el-Sheikh Governorate the North Delta region is considered one of the most important areas in Egypt affected by salts. Salinity is a significant constraint that limits tomato productivity and tomatoes are only moderately salt-tolerant. Five parental cultivars (Edkawy, Castle Rock, CLN2498E, SuperMarmand, Super Strain B). Diallel crosses to produce F1 hybrids, leading to evaluation of genotypes. The experiment was laid out in Completely Randomized Design (C.R.D.) with three replications, A two-factor pot experiment in a greenhouse (2022/2023 and 2023/2024), Factor A: 15 genotypes (5 parents + 10 hybrids) and Factor B: Four salinity treatments (control plus three salinity levels) Design with Each genotype-treatment combination replicated three times (total: 180 pots). Results Significant positive GCA for chlorophyll Castle Rock (P2) and SuperMarmand (P4) were strong general combiners. Strong SCA Hybrids such as P1×P3, P2×P3, and P3×P5 showed high SCA for chlorophyll and/or proline, revealing favorable specific combinations for stress tolerance through osmolyte accumulation. Na⁺/K⁺ Ratio and Ascorbic Acid SCA variances generally exceeded GCA, indicating non-additive gene action was predominant. Nevertheless, some parents displayed positive GCA effects for ascorbic acid content, while favorable SCA for reduced Na⁺/K⁺ ratio and increased ascorbic acid appeared in crosses such as P1×P2, P2×P3, and P4×P5. Yield Traits SCA mean squares surpassed GCA under all conditions; low GCA/SCA ratios (<0.12) reinforce the dominance of non-additive gene action for yield, highlighting the importance of heterosis and hybrid development Breeding Objectives Efforts focus on developing F1 hybrids with both high yield and improved tolerance to salinity by analyzing gene actions and inheritance.