Six tomato (Lycopersicon esculentum Mill.) genotypes were used. To study the magnitude of gene effcts and the distribution of both recessive and dominant genes controlling the morphological, physiological, quality and yield characters among the  six tomato These genotypes included the two isogenic lines 83 and 80, the commercial Sherry tomato and another three varieties namely, Super Marmand, Pretchard and Money Maker.
Recessive genes were found to be  higher in frequency than dominant ones in the parents for number of branches, number of leaves, dry stem weight, dry leaves weight per plant, titratable acidity, number of fruits per plant, plant growth rate and leaf area. However, more dominant genes were involved in controlling the rest of characters.  Plant height and total fruits weight are controlled by the largest number of dominant gene groups, (14 and 15, respectively). Meanwhile, leaf area, carotenoids content, fruit shape index, pericarp thickness and ascorbic acid content were controlled by the least number of dominant gene groups. Number of branches, number of leaves, leaf area, dry stem weight, dry leaves weight and quality and yield characters had moderate to high heritability estimates except for total soluble solids, which had the least narrow-sense heritability estimate (0.14).
Association type of gene distribution was observed for average fruit weight, carotenoids content, fruit shape index, number of locules and pericarp thickness. But non-random gene distribution of the dispersion type might be mainly controlling the characters of plant height, number of branches per plant, number of leaves per plant, dry stem weight per plant, dry leaves weight, chlorophyll A content and total fruits weight per plant. Complementary type of interaction was observed among genes of the parents for leaf area and chlorophyll B content. An overestimation of the degree of dominance was observed for leaf area, plant growth rate and number of branches per plant. Meanwhile, underestimation of the degree of dominance was observed for pericarp thickness.