الفهرس 
IntroductionOnly 14 pages are availabe for public view
 |  | from | 241 |  |  |
| | | from | 241 | | |
Abstract
The present investigation was carried out during 2007 and 2008 rice growing seasons at the Research Farm of Rice Research and Training Center (RRTC), Sakha, Kafr El-Sheikh , Egypt, to study: 1- The mean heterosis effect as a deviation from both mid-parent and better-parent. 2- general and specific combining ability effects. 3- phenotypic correlation coefficients among all possible pairs of the studied characters, under water stress and normal conditions. Eight rice varieties namely, Sakha 102, Sakha 104, Balado, Wab 450, IET1444, Wab 878, Gaori and GZ 1368 were crossed in all possible combinations excluding reciprocals according to Griffin’s (1956), method (2), model (1). . The obtained results can be summarized as follows: 1- Highly significant and positive estimated of heterosis when it computed as a deviation from mid-parent and better-parent were obtained in the cross IET1444 x Wab 878 for grain yield and most of its components under both conditions. While, the cross Wab 450 x GZ 1368 exhibited highest positive heterosis for most of root characters under both conditions. Moreover, the cross Sakha 104 x GZ 1368 exhibited highest positive heterosis for chlorophyll content under both conditions. significant and negative estimated of heterosis were desirable in the crosses Wab 450 x Wab 878, Wab 450 x GZ 1368 and Wab 878 x GZ 1368 under water stress and Sakha 102 x Wab 878 under normal conditions for number of days to 50% heading (earliness) when it measured as a deviation from mid-parent and better-parent. One cross namely; Gaori x GZ 1368 exhibited highest negative heterosis for amylose content under both conditions. 2- The rice varieties IET 1444, Wab 450 and Balado were the best general combiners for yield and most of its components, under water stress conditions. While, the variety Balado was the best general combiner for yield and most of its components, under normal conditions. Moreover, the rice variety IET 1444 was the best general combiner for most of root characters under both conditions. The rice varieties Sakha 104, Wab 878, Gaori and GZ 1368 were the best general combiners for most of grain quality characters under both conditions. The varieties Sakha 102, Balado and Gaori were the best general combiners for earliness under both conditions. . 3- The cross Wab 878 x Gaori were the best cross combination for yield and most of its components under both conditions. Moreover, IET1444 x Gaori cross were the best cross combination for most of root and grain quality characters under both conditions. The crosses Sakha 102 x Sakha 104, Balado x IET1444 and Wab 450 x Wab 878 were the best crosses combinations for earliness under both conditions. The cross Sakha 104 x GZ 1368 were the best cross combination for chlorophyll content under both conditions. 4- Grain yield/plant was significant or highly significant and positively correlated with nine characters, these characters were number of panicles/plant, panicle length, 100-grain weight, root length, root volume, root/shoot ratio, chlorophyll content, grain length and milling % under both conditions. On the contrary, grain yield/plant was significant and negatively correlated with sterility % and leaf rolling under both conditions