Tomatoes is one of the most important vegetable crop not only in Egypt, but also all over the world. Therefore, there are many different continues effort to produce superior hybrids and varieties. In this respect, the present investigation was directed to exploit the amounts of heterosis that could be obtained from the hybrids and determine the nature of gene action associated with it using Mather and Jinks (1982) scaling test. For this purpose, four varieties were used. These varieties were: Edkawy (P1), Super streen B (P2), Peto 86 (P3) and Flourdade (P4). Three hybrids were obtain during 2009 growing season by crossing Edkawy with each of the other three varieties to produce three different hybrids. In the growing season of 2010, each hybrid was used to generate six populations which included(P1, P2,F1,F2, BC1 and BC2). Amounts of heterosis from mid – parent were 100.3 and 62.3% for the hybrid (P1 X P2) indicating that it had the heaviest fruit weight per plant and No. of fruits/plant. The hybrid (P1 X P4) gave (16%), for shape index. The hybrid (P1 X P3)gave (43.2%), for hardness in kg.
For chemical traits, the hybrid (P1 X P4) gave 17.09 for total soluble soileds .The best hybrid for lycopene and ascorbic acid were the hybrid (P1 X P2) which gave 129.2 and 15.7% , respectively.
Proportion amounts of heterosis from better -parent were 64.4 and 38.4 for the hybrid (P1 X P2) indicating that it had the heaviest fruit weight per plant and No. of fruits/plant.The hybrid (P1 X P4)gave 25%, for hardness in kg.
For chemical traits, the hybrid (P1 X P4) gave 14.0 %for total soluble soiled .The best hybrid for lycopene and ascorbic acid was the hybrid (P1 X P2) which gave 75.6 and -19.0% , respectively. In the same time , all the F2 generations showed inbreeding depression.
The six population were setup in scaling test analyses to determine the nature of gene action and to test the adequacy of additive dominance model.