This study was implemented during three successive seasons; 2011, 2012 and 2013 at the experimental farm of Rice Research and Training Center, Sakha, Kafr El-Sheikh, Egypt. Six rice genotypes with different water stress tolerance were crossed Three crosses viz; cross I {Tsuyuake (tolerant) X Sakha 103 (sensitive)} were produced, cross II {Zenith (tolerant) X Sakha 104 (moderate)} and cross III {BL1 (moderate) X Sakha 106 (sensitive)}. Six populations of P1, P2, F1, BC1, BC2, and F2 for each cross were used in the present study. Results indicated that high differences between the six parents for all root characters, as well as, grain yield and its related traits under water stress conditions. Parent Tsuyuake gave the highest mean values for most of the studied traits, while, the lowest mean values were recorded for Sakha 106 rice cultivar. Highly significant positive heterosis and heterobeltiosis was estimated for some root characters and grain yield and its component especially in crosses I and II. Negative over dominance were recorded for root fresh weight, days to 50% heading, plant height and grain yield/plant in cross III, as well as, 100 grain weight in the three crosses and sterility percentage in crosses I and III. Low and positive inbreeding depression values were estimated for 100 grain weight in crosses I and III. Epistatic gene effect had a significant contribution in inheritance of all studied characters. Additive genetic variance was greater than the dominance genetic variance for root volume and grain yield/plant in cross II, root fresh weight and days to 50% heading in crosses II and III, root / shoot ratio in crosses I and III ,as well as, plant height and panicle length in the three crosses. Heritability in broad sense ranged from low to intermediate and high in the three crosses but was low in narrow sense. Low predicted genetic advance (3.99) for root number / plant to high value (30.15) for root length in the cross III were found. Tsuyuake and Zenith may be useful genotypes in breeding program for water stress condition. This conclusion might be useful for rice breeders in planning a selection program for improving root characters and productivity of rice under stress conditions.