This present investigation was carried out at Food Legumes Department, Sakha Agricultural Research Station, Agriculture Research Center, Egypt, in summer 2016 and 2017 seasons. Six parental genotypes of soybean were used in this study. In 2016, the Six soybean genotypes were used as parents in half diallel cross mating design. In the second season, the experimental were conducted to evaluate the yield potential and agronomic performance of the obtained F1's hybrids of the fifteen crosses compared with their parents. The results could be summarized as follows: Mean squares for genotypes, General and specific combining ability were highly significant for all the studied traits. The parental line L75-6648 was the best of tested parent in flowering and maturity dates. Also, the crosses Giza111 X Giza21 and L75-6648 X Giza21 , exhibited the lowest mean values for these traits. The parental L75-6648 as well as the crosses L75-6648 X Giza111 and Toano X Giza111, were taller in plant height than their parental means. For number of pods and seeds per plant, the parents Giza111 and Giza21 as well as the crosses Pershing X Giza111 and Holladay X Giza21 gave the highest values for number of pods and seeds per plant. For seed yield per plant, the two parents, Giza21 and Giza111 gave the highest values of this trait. The crosses Pershing X Giza111, Toano X Giza111, Holladay X Giza21 and Giza111X Giza21 gave the highest values for seed yield/plant. The parental variety Giza111(P5) gave significant negative (gi) effects for flowering and maturity dates.

The present study was carried out at Sakha farm, Sakha Agricultural Research Station (SARS), Kafr El-Sheikh, Egypt, during the three summer seasons of 2017, 2018 and 2019. Four crosses of soybean, each with six populations (P1, P2, F1, Bc1, Bc2 and F2) were tested for yield and some growth attributes. The results showed that: Over dominance was observed for flowering date in crosses I and II, for maturity date and plant height in cross II and seed yield per plant in all crosses, while partial dominance was observed for the remaining crosses for most traits. Significant negative heterosis were detected for flowering date for mid-parent in the first cross, significant positive heterotic effects were detected for other traits. The additive effect (a) was highly significant in positive or negative direction in all crosses for all traits, except in the four crosses for number of seeds per pod and 100 seed weight, crosses I and II for flowering date. Additive x additive types of gene action were found to be significant for most traits of all crosses, also additive x dominance and dominance x dominance types of gene effects were found to be significant for most traits. High narrow sense heritability values were obtained for plant height and number of seeds per pod in the first cross. While, the lowest estimates was resulted for number of seeds per pod in the second cross, number of branches per plant in the first cross and seed yield per plant in the fourth cross.