الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
 |  | from | 127 |  |  |
| | | from | 127 | | |
Abstract
To study the heterosis and combining ability of bread wheat under different irrigations treatments seven parental genotypes of bread wheat (triticum eastivum (L.)) namely; (Gemmiza 11, Sids 1, Gemmiza 12, Sohag 1, Line 1, Giza 171 and Sakha 94) crossed in a half diallel mating design and all possible F1 crosses and their parents were separated in two field experiments were conducted at Etay EL-Baroud Agriculture Research Station, EL-Behaira, Egypt during two growing season of 2016-2017 and 2017-2018. In the first experiment all genotypes (parents and F1) were irrigated once a time at sowing while, in the second experiment all genotypes had a full irrigation (three times during the growing season). The obtained results of this study could be summarized as follows: 1- Ordinary analysis of variance. Mean squares for the two irrigation treatments were found to be highly significant for all traits studied except number of spikelets/spike. Mean squares due genotypes were found to be highly significant for all studied traits at the two irrigation treatments as well as their combined analysis except for spike length under stress irrigation in the combined analysis. Mean square due genotypes vs. irrigation treatments were also found to be highly significant for all studies traits except for spike length. Mean squares due to parents were found to be highly significant for all traits studied at the two irrigation treatments and their combined analysis except for spike length under stress irrigation and number of spikelets/spike under normal irrigation. In the same way, mean squares due to parents x irrigation treatments were highly significant for all studied traits except spike length. Data indicated that the crosses mean squares were found to be highly significant for all traits studied at the two irrigation treatments as well as their combined analysis except for spike length under stress irrigation. Mean squares due to crosses x irrigation treatments found to be significant for all studied traits except for spike length in the combined analysis. 2- Mean performances: Data indicated that Gemmiza 11 and the Line 1 showed the most desirable values for earliness where it gave the lowest averages for heading date, maturity date and maturity periods among all tested parents under both irrigation treatments and their combined data. the cross combinations Gemmiza 11 x Sohag 1 and Line 1 x Sakha 94 showed the lowest number of days to heading under stress irrigation, while the cross Sids 1 x Sakha 94 showed the lowest number of days to heading under normal irrigation and combined data. Gemmiza 11x Sids 1 was the earliest among all tested crosses under stress irrigation and combined data while, the cross Sohag 1 x Giza 171 was the earliest one among all tested crosses under normal irrigation, while the cross Sids 1 x Sakha 94 showed the lowest number of days to maturity under normal irrigation and combined data. Data showed that, Giza 171 and Line 1 had the highest grain yield/plant and most of its components in both irrigations treatments and their combined data. As for crosses, the highest grain yield/plant were shown in the crosses Giza 171 x Sakha 94 followed by Line 1 x Giza 171 then Sids 1 x Sohag 1 showed the most desirable means for seed yield and some of its components in both irrigations treatments and their combined data. The obtained results showed that, the highest straw yield/plant was obtained by Gemmiza12 and Sakha 94 in both irrigations treatments and their combined data. As for crosses, the highest straw yield/plant were shown in the crosses Sids 1 x Sakha 94 under normal irrigation and the combined data and the cross Line 1 x Giza 171 under stress irrigation. The obtained results showed that, the highest harvest index was obtained by Gemmiza 12 under stress irrigation and the combined data and Giza 171 in both irrigations treatments and their combined data. As for crosses, the highest harvest index was shown in the crosses Sids 1 x Sohag 1 and Giza 171 x Sakha 94 in both irrigations treatments and their combined data. 3- Heterotic effects: parents vs. crosses mean squares indicated that the average heterosis overall crosses were found to be highly significant for all traits studied at the two irrigation treatments and their combined data except for maturity date and 1000-grains weight under stress irrigation, number of spikes/plant, spike length and straw yield/plant under normal irrigation, plant height and leaf area/plant in the combined analysis, number of grain/spike under stress irrigation and the combined analysis and harvest index in both irrigations treatments and their combined analysis. The mean square due to average heterosis x irrigation treatments (parent x crosses x irrigation treatments) was found to be significant for all studied traits except for heading date, maturity period, tillers number/plant, relative water content, total phenols, spike weight, number of spikelets/spike, number of grains/spike, biological yield/plant, straw yield/plant and harvest index. o Results indicated that, the most negative desirable significant heterotic effects for earliness were presented in the three crosses Gemmiza 11x Sids 1, Gemmiza 11x Gemmiza 12 and Sohag 1 x Giza 171 in both irrigations treatments and their combined analysis. o The presented results indicated that, the most positive significant desirable heterotic effects for grain yield/plant were shown by the two crosses Sids 1 x Sohag 1 and Giza 171 x Sakha 94 under the stress and normal irrigations as well as their combined analysis. o Results showed that, the most positive significant desirable heterotic effects for straw yield/plant were obtained by only the cross Gemmiza 12 x Giza 171 under the stress and normal irrigations as well as their combined analysis. o Results showed that, the most positive significant desirable heterotic effects for harvest index were obtained by the three crosses Sids 1 x Sohag 1, Line 1 x Sakha 94 and Giza 171 x Sakha 94 under the stress and normal irrigations as well as their combined analysis.