Genetic behaviour for some root characters and their relation to some yield other characters under drought condition in rice, Oryza sativa L.

The results indicated that high differences between the six parents for most of studied characters were determined. The rice variety RD 23 owned the highest mean values for most of all studied traits, while the lowest mean values were recorded for rice variety Sakha 103. Highly significant positive heterosis and heterobeltiosis were estimated for root characters. Over-dominance played an important role in the inheritance of root length, root number, root volume and root fresh weight in cross 1 Low and positive inbreeding depression values were estimated in the last two crosses, while moderate estimates were found in the first cross. Epistatic gene effect had a significant contribution of inheritance in most studied characters. The additive X additive gene interaction appears to contribute more than any other sources of epitasis. Additive genetic variance was greater than the dominance genetic variance. Heritability in broad sense was ranged from low to high in the three studied crosses. While narrow sense heritability was moderate to low. The highest value of heritability estimates (58.54) was recorded for root length in cross II, Moderate to high values of predicted genetic advance were estimated for all studied crosses, these values 30.21 for root dry weight in cross II. Significant or highly significant positive phenotypic correlation was found between most of all studied characters in the three studied crosses especially between root characters and grain yield / plant under drought condition. Concerning water saving, The results showed that the highest crop water use efficiency were 0.66 and 0.62 kg / m. recorded from 1 m. flashing water irrigation it cross, I (RD23 x Sakha 102) and cross II (BG35 X Giza 177). Therefore these crosses could be recommended to be grown under drought condition to obtain the highest rice grain yield Kg/m. and highest value of save water in the same time.