The present study was carried out during 2017 and 2018 seasons at the experimental farm of Agricultural Station of Etay El-Barood, EL-Behira overnorate, Egypt. Six soybeans parental genotypes and their 15 F1 were evaluated for seed yield and some of its attributes under normal irrigation conditions (irrigate every 15 days) and stress irrigation conditions (irrigate every 30 days) to select the best genotypes (parents and crosses) had high yield under water stress conditions. Also, to determine the type of gene action involving seed yield and yield components traits and the method of selection for the best crosses in segregation generations under normal and stress irrigations conditions. The results indicated that mean square for genotypes, parents, crosses, parents vs. crosses, genotypes x irrigation, parents x irrigation, F1 x irrigation and parents x F1 x irrigation were significant for all studied traits under both irrigation treatments and the combined analysis except parents vs. crosses for maturity date under normal irrigation. The two parents D89-8940 and Line162 and the two crosses D89-8940 x Line162 and Dr101 x Line162 recorded the highest seed yield/plant (g) in both irrigation treatments and the combined analysis. Our results indicated that mean square associated with general combining ability (GCA) and specific combining ability (SCA) were significant for all studied traits under normal, stress conditions and combined analysis except SCA for main root length cm under normal irrigation condition. The highly GCA/SCA ratio more than the unity was observed for all studied traits which may indicate that the largest part of the total genetic variability associated with these traits a result of additive and additive x additive. The parental genotypes D89-8940, Dr101 and Line162 seemed to be excellent combiners for seed yield/plant and most other traits under normal, stress and the combined analysis. The most desirable Ŝij effects for seed yield/plant were recorded by the cross Dr101 x Line162 flowed by Lkota x Dr101 and Dr101 x Giza21. It could be recommended to use the pedigree method to select the superior crosses for high yield in the segregation generation under both normal and drought conditions.
