الفهرس 
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Abstract
Objectives : The present investigation was carried out during 2011and 2012 rice growing seasons at the Lysimeter and the Research Farm of Rice Research and Training Center (RRTC), Sakha, Kafr El-Sheikh, Egypt, to study:
1- The mean performance and heterosis effect as a deviation from both mid-parents and better-parent under saline and normal conditions.
2- General and specific combining ability effects under saline and normal conditions.
3- Phenotypic correlation coefficients among all possible pairs of the studied characters, under saline and normal conditions.
Methods & Results:
Sixteen rice varieties namely, Sakha 102, Sakha 104, Giza 178 (testers) , Wab 880SG-33, IET 1444, Wab 880-P1, Gaori, GZ 1368-S-5-4, Giza 177, Giza 182, Sakha 105, Sakha 106, Suweon 345, Agami M1, BG 34-8 and Yabani lulu (lines) were crossed in line x tester.
Fourteen characters were investigated and divided into three main groups as follows:
1- Vegetative, yield and its components characters: i.e., days to 50 % heading, plant height (cm), number of panicles/plant, 1000-grain weight (g), number of filled grains/panicle, salinity tolerance index, sterility (%) and grain yield/plant (g).
2- Root characters, i.e., root length (cm), number of roots/plant and Root/Shoot ratio.
3- Grain quality characters, i.e., grain shape, milling % and amylose content %.
The salient feature of the present investigation are summarized as follows:
1- The genotypes, Giza 178 under normal condition, and Gz 1368-S-5-4 under the two levels of salinity, recorded the highest mean values of grain yield/plant. On the other hand, the highest mean values were recorded by two crosses Gz 1368-S-5-4 × Giza 178 under normal condition and IEET 1444 × Sakha 104 under the two salinity levels (S1 and S2).
2-Highly significant and positive estimated of heterosis when it computed as a deviation from mid-parents and better-parent were obtained in the crosses Wab 880SG-33 x Sakha 104, IET 1444 x Sakha 104, Sakha 106 x Giza 178, Sakha 105 x Giza 178, Suweon 345 x Giza 178, Gz 1368-S-5-4 x Giza 178, BG 34-8 x Giza 178 and Agami M1 x Sakha 102 for grain yield and most of its components under all conditions.
3- The rice varieties IET 1444, Gz 1368-S-5-4, Giza 178, Suweon 345 and Sakha 105 were the best general combiners for grain yield/plant under normal condition. While, the varieties IET 1444, Gz 1368-S-5-4, Giza 178 and Agami M1 were the best general combiners for grain yield/plant under level S1 condition. Moreover, the rice variety IET 1444 and Gz 1368-S-5-4 were the best general combiners for grain yield/plant under level S2 condition.
4- The crosses Wab 880SG-33 x Sakha 104, Sakha 106 x Giza 178, Sakha 105 x Giza 178, Gz 1368-S-5-4, Agami M1 x Sakha 102 and Yabani lulu x Sakha 102 were the best cross combinations for grain yield/plant under normal and two levels of salinity
5- Grain yield/plant was significant or highly significant and positively correlated with days to 50 % heading, no. of panicles/plant, no. of grains/panicle, 1000-grain weight, root length, no. of roots/plant, root/shoot ratio, and grain shape under normal condition and with plant height, no. of panicles/plant, no. of grains/panicle, 1000-grain weight, grain shape, root length, no. of roots/plant and root/shoot ratio under level S1condition, and with no. of panicles/plant, no. of grains/panicle, 1000-grain weight, grain shape, root length and no. of roots/plant under level S2 condition. While it was negatively associated with sterility % under both S1 and S2 of salinity conditions.
Conclusion:
The results revealed that IEET 1444, Gz 1368-S-5-4 and Giza 178 rice genotypes were the best general combiners for the most of the studied traits under all conditions. However, the results also exhibited that Wab 880SG-33 x Sakha 104, IEET 1444 x Sakha 104 and Gz 1368-S-5-4 x Giza 178 were the best specific cross combinations for the most studied traits including grain yield/ plant under all conditions. Hence, the Egyptian rice breeders might concentrate on these combinations for improving most the studied traits in their breeding program.