Eight local and exotic cultivars of rice were crossed to obtain 28 F1 crosses, through half diallel mating design. The eight parents and their 28 F1s ( excluding reciprocals) were grown in a randomized block design with three replications at the farm of Sakha Research Station, Sakha, Kafr El-Sheikh, Egypt in 2020 and 2021 rice seasons. GCA and SCA were significant for most of studied traits. GCA/SCA ratios were found to be less than unity for all studied traits, indicating that the non-additive type of gene action was great importance in the inheritance of these traits. Estimates of GCA effects indicated that, the parent IET1444 was a good general combiner for most of studied characters. The hybrid combinations IR 65600-77×Nerica 9 were the best SCA for most of studied characters. IR 65600-77×Nerica 9 rice hybrid exhibited significant and highly significant positive estimates of heterosis as a deviation from mid and better parent for root length, number of roots/plant, root volume, root/shoot ratio, relative water content, flag leaf area, number of panicles/plant, 1000-grain weight and grain yield/plant under water deficit conditions, except root length for better parent was insignificant.
Six rice genotypes with different drought tolerance were crossed. Six populations (P1, P2, F1, F2, BC1 and BC2) of three rice crosses namely Giza 177 x Giza 178 (cross I); Sakha 103 x WAB 880 SG 33 (cross II) and Sakha 104 x IET 1444 (cross III) were raised in a randomized complete block design with three replications during the three successive summer seasons from 2010 to 2012 at the Farm of Rice Research and Training Center Sakha, Kafer El-Sheikh, Egypt. This study aimed to determine the heterosis, gene action, heritability, genetic advance and phenotypic correlation response to selection and prediction by the new lines for the traits of days to 50 % heading, plant height, panicle length, number of panicles/ plant, number of filled grains/ panicle, 100-grain weight, sterility % and grain yield/ plant. Flashing water irrigation was added every 10 days intervals. The results obtained from the mean of parents, F1 and F2 generations showed wide range in mean values between the parents and the presence of partial and overdominance were found for all studied characters. Significant and highly significant positive estimates as a deviation from mid and better parents in all crosses for panicle length, number of panicles/ plant and grain yield/ plant, also highly significant positive estimates as a deviation from mid and better parents in the first two crosses for plant height. Scaling test provide evidence of non-allelic interaction in controlling all the characters studied in most crosses, the additive gene effect (d) was more important in the genetic system for all studied characters, dominance gene effects (h) and additive x additive gene effects (i) were played an important role in the inheritance of plant height, panicle length, number of filled grains/ panicle, 100-grain weight, sterility % and grain yield/ plant. The additive x dominance (j) were significant and involved in the inheritance of days to 50 % heading, plant height, number of panicles/ plant, number of filled grains/ panicle, 100-grain weight, sterility % and grain yield/ plant. However, the dominance x dominance (l) were involved in the genetic control of all characters. Heritability estimates in broad sense were high. Meanwhile, heritability estimates in narrow sense were mostly low. The maximum genetic advance of the mean values was found to be high for number of panicles/ plant, plant height and days to 50 % heading characters. Highly significant and positive correlation was found for grain yield/ plant with panicle length, number of panicles/ plant, number of filled grains/ panicle and 100-grain weight in all studied crosses. From the foregoing results, cross II (Sakha 103 x WAB 880 SG 33) and cross III (Sakha 104 x IET1444) could be recommended for growing under water deficiency to obtain the highest rice grain yield and the highest values of saving water at the same time.
Eight genotypes cultivars of rice were crossed to obtain 15 F 1 crosses, through line x tester mating design was employed for this purpose. The experiment was carried out using line x tester mating design, during 2021 and 2022 rice growing seasons at the experimental farm of Sakha Research Station, Sakha, Kafr El-Sheikh, Egypt. Both GCA and SCA variances were found to be significant or highly significant for all studied traits. The estimates of GCA effects indicated that, the parent IR 12 G 3222 was a good general combiner for root length, number of roots/plant, and flag leaf area under both conditions. In addition, GZ 1368 was a good combiner for root volume under both conditions. While the line IR 69432 was a good combiner for root/shoot ratio under water deficit condition. The line 11 L 236 for chlorophyll content, number of filled grains/panicle, grain yield/plant and the tester Giza 178 for relative water content and grain yield/plant were good combiners under both conditions. On the other hand, the cross combinations, IR 69432 X GZ 1368 was found to be the best specific combinations for root length, number of roots/plant, root volume and root/shoot ratio under two conditions. The cross combination, IR 12 G 3213 X Giza 178 was the best specific combinations for relative water content, flag leaf area and chlorophyll content under both conditions . The cross combination, IR 12 G 3222 X Giza 178 was the best specific combination for 1000-grain weight and fertility % under both conditions. In addition, the cross combination, IR 69432 X GZ 1368 under normal and IR 69432 X Nerica 7 under water deficit were the best specific combinations for grain yield/plant. On the other hand, the crosses, IR
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