الفهرس 
IntroductionOnly 14 pages are availabe for public view
 |  | from | 169 |  |  |
| | | from | 169 | | |
Abstract
The objective of this work was to study the genetics behavior of some economic traits in some of the bread wheat genotypes cultivated in Egypt under normal and water-stress conditions. Studies were carried out using the full-diallel crosses (without reciprocal) analysis among eight varieties of bread wheat Triticum asetivum L. [Sids-1 (P1), Sakha-93 (P2), Giza-168 (P3), Sakha-69 (P4), Irena (P5), Giza-164 (P6), Gemmiza-9 (P7) and Giza-165 (P8)]. The fieldwork was carried out from 2001 to 2004 at the Experimental Farm of Mallawy Agricultural Research Station (clay/loam soil), Agricultural Research Center, Ministry of Agriculture, Egypt. The obtained results can be summarized as follows:
A- Genetic behaviour of grain yield and its attributes:
1- Plant height (cm)
The results indicated that Sids-1 (P1 parent) surpassed the other parents in plant height under normal (118.00 cm) and water-stress (108.33 cm) conditions. Also the crosses P1P2 under normal condition (120.67 cm) and P5P8 under drought condition (117.33 cm) in the F1 generation as well as P5P8 under normal condition (117.33 cm) and P2P6 under drought condition (110.76 cm) in the F2 have all surpassed the other corresponding crosses.
In terms of heterosis effect, the two crosses, P2P5 under normal condition (13.43%) and P3P5 under drought condition (15.18%) were the most superior in plant height for mid-parent heterosis, and the crosses P2P5 under normal condition (9.12%) and P3P5 under drought condition (12.58%) for the better parent heterosis.
Regarding inbreeding depression (ID%) for F2 generation, two crosses showed the least decrease in plant height i.e. P5P8 (2.28%) and P1P3 (1.21%) under normal and drought conditions, respectively.
Two parents showed that they are good combiners according to their values of GCA, i.e. Sids-1 (P1) under normal condition and Giza-165 (P8) under drought condition. Also two crosses, P3P4 under normal condition and P1P2 under drought condition were both superior in their performance as SCA to plant height.
Estimates of the genetic parameters, showed that the additive and non-additive gene effects are both included as main factors affecting plant height. However, the non-additive effect was bigger than the additive effect. When the F2 was grown under normal and drought conditions it showed different types of non-allelic gene interactions, i.e. the duplicate type under normal condition, and the complementary type under drought condition. The relationship between Wr/Vr indicated that, there are over dominance in F1 under normal and drought conditions, and in F2 under drought condition. It also indicated complete dominance for F2 under normal condition.
The values of narrow sense heritability were relatively low under both conditions for F1 generation (i.e. 0.0664 under drought condition and 0.0067 under normal conditions). For F2 generation it was 0.0184 under drought condition and 0.0137 under normal condition.
2- Number of spikes/plant (s/p)
The results indicated that Giza-168 (P3) and Sids-1 (P1) parents surpassed the other parents in number of spikes/plant (s/p), under normal (21.97) and drought (20.67) conditions, respectively. The cross P1P8 surpassed the other crosses in s/p, (27.87) in F1 and (23.04) in F2 under normal condition. Under drought condition the crosses P3P8 (24.17) in F1 and P1P8 (21.90) in F2 have surpassed the other crosses.
In terms of heterosis effect, the two crosses, P1P6 under normal condition (41.11%) and P3P8 under drought condition (29.46%) were the most superior in s/p for mid-parent heterosis, and the crosses P5P6 under normal condition (32.26%) and P2P4 under drought condition (27.55%) for the better parent heterosis.
Regarding ID% for F2, the least decrease of s/p was shown by P4P7 (4.29%) under normal and P4P6 (5.84%) under drought conditions.
The results of GCA showed that Giza-168 (P3) and Sids-1 (P1) were good combiners under normal and stress conditions, respectively. However, Sakha-93 (P2) was the poorest combiner under both conditions. Also the two crosses, P1P6 under normal condition and P3P8 under drought condition were both superior in their performance as SCA to number of spikes per plant.
Estimates of genetic parameters showed that the additive and non-additive gene effects were both main factors affecting s/p and that the non-additive effect is bigger than the additive effect. The type of dominance controlling this trait was over for F1 and F2 under both environmental conditions. The type of non-allelic interaction was complementary for F1 and F2 under normal condition as well as for F2 under drought condition. The relationship between Wr/Vr indicated that, there are over dominance in F1 under normal and drought conditions, and F2 under drought condition, while it was partial dominance for F2 under normal condition.
The values of narrow sense heritability for F1 were relatively low under both, normal 0.300 and drought condition 0.078. For F2 it was 0.583 under drought condition followed by 0.514 under normal condition.
3- Number of kernels/spike (k/s)
The results of the performance indicated that Sids-1 (P1) parent surpassed the others in number of kernels/spike (k/s), under normal (94.97 k/s) and drought (89.87 k/s) conditions. Meanwhile 3 crosses surpassed the other crosses in k/s. These are the cross P1P8 in both F1 (99.23 k/s) and F2 (95.47 k/s) under normal condition, the cross P3P6 (96.53 k/s) in F1 under drought condition and the cross P2×P6 (92.37 k/s) in F2 under drought condition.
In respect of the drought susceptibility index (DSI), Giza-164 (P6) was the best parent in F1 (0.62) and in F2 (0.83), respectively, while crosses, P5P7 in F1 (0.11) and P3P6 in F2 (0.08) were the best for this index i.e. DSI.
According to the heterosis effect, the cross P4P6 (15.95%) under normal condition and P4P6 (18.95%) under drought condition were the most superior crosses for mid-parent heterosis, while the cross P2P6 (13.51%) under normal condition and P4P6 (15.35%) under drought condition were the most superior crosses according to the better parent heterosis.
Regarding ID% for F2, the least decrease of k/s, was shown by the two crosses P5P7 (1.22%) and P2P5 (0.07%) under normal and drought conditions, respectively.
Three parents showed that they are good combiners according to their values of GCA, Giza-168 (P3) under normal condition, Irena (P5) under drought condition, Giza-164 (P6) for DSI. As for SCA, also 3 crosses, (P1P8 under normal condition, P4P6 under drought condition and P5P7 for F1DSI) confirmed that they are superior in their SCA performance.
The estimated genetic parameters, showed that both additive and non-additive gene effects are of the main factors affecting k/s and that the non-additive effect is bigger than the additive effect. The type of dominance involved in controlling this trait is over-dominance for F1 and F2 under normal condition. Both F1 and F2 grown under normal and drought conditions showed different types of non-allelic gene interactions. Two types of non-allelic gene interactions were indicated for k/s i.e. the first is duplicate type which appeared in F1 under drought condition and DSI, F2 under drought condition and DSI, while the second is complementary type which appeared in just one case, F2 under normal condition. The relationship between Wr/Vr indicated that, there are over dominance in F1 and F2 generations under normal condition.
The values of narrow sense heritability were relatively low under both conditions except for DSI in F2 which was 0.522. Heritability was 0.281 for F2 under drought condition, 0.269 for DSI in F1, 0.258 for F2 under normal condition, and 0.111 for F1 under drought condition. The lowest was 0.015 for F1 under normal condition.
4- 1000 kernels weight (g)
The results of the performance indicated that Sids-1 (P1) under drought condition (44.06g), and Giza-165 (P8) under normal condition (46.09g) surpassed the other parents in 1000 kernels weight. Meanwhile 3 crosses surpassed the other crosses in 1000 kernels weight, P7P8 (52.68g and 48.12 g) in F1 under normal and drought conditions, respectively, P4P6 in F2 under normal condition (48.70g) and P3P6 in F2 under drought condition (45.01g).
In respect of drought susceptibility index (DSI), Sakha-69 (P4) was the best parent (0.14), while P2P4 was the best cross in F1 (0.24).
In heterosis, P4P5 under normal and drought conditions, were the most superior cross in 1000 kernels weight for mid-parent heterosis (18.45%, 23.08%) respectively. P4P5 (17.80%) under normal and P3P6 (16.99%) under drought conditions were the most superiors for better-parent heterosis.
Regarding to ID% for F2, two crosses confirm the least decrease of 1000 kernels weight, P1P5 (0.94%) under normal condition and P2P7 (2.31%) under drought condition.
Two parents showed that they are good combiners according to their values of GCA i.e. Sakha-69 (P4) under drought condition (and the same parent for DSI) and Gemmiza-9 (P7) under normal condition. As for SCA, also 2 crosses, (P7P8 under normal and drought conditions and P3P5 for F1DSI) confirmed that they are superiors in their SCA performance in 1000 kernels weight.
Estimates of the genetic parameters, showed that the additive and non-additive gene effects are acting as main factors affecting 1000 kernels weight and that the non-additive effect is bigger than the additive effect except for DSI in F1 in which H1 was smaller than D indicating partial dominance effect. The type of dominance involved in controlling this trait is over-dominance for F1 under both conditions and F2 under drought condition. Both F1 and F2 grown under normal and drought conditions showed different types of non-allelic gene interactions. Two types of non-allelic gene interactions were detected for 1000 kernels weight i.e. the duplicate type which appeared in F1 under normal condition and F1 DSI and the complementary type which appeared in F1 under drought condition and F2 under normal condition. The relationship between Wr/Vr indicated that, there is over dominance in F1 under both conditions and F2 under drought condition and this is partial dominance for F2 under normal condition and for DSI in F1.
The values of narrow sense heritability were relatively low or very low under both conditions where, for F2 under drought and normal conditions they were 0.424 and 0.423 respectively. While for F1 they were 0.097, 0.036 and 0.034 for DSI, under normal and drought conditions, respectively.
5- Grain yield/plant (g)
The results of the performance indicated that Giza-168 (P3) under normal condition (52.18 g) and Sids-1 (P1) under drought condition (40.57 g) surpassed the other parents in grain yield per plant. Meanwhile some crosses surpassed the other crosses in grain yield/plant i.e. P1P8 (77.53g) in F1 under normal and drought conditions (68.17g) and P3P6 (60.40g) under normal condition in F2 and P7P8 (54.20g) under drought condition in F2.
Moreover, Sakha-93 (P2) was the best parent for DSI (0.06 in F1 and 0.07 in F2), and P4P7 cross for DSI in F1 (0.12), and P5P8 for DSI in F2 (0.03).
In heterosis, P5P6 (69.71%) under normal condition and P7P8 (71.10%) under drought condition were the most superior crosses in grain yield/plant for mid-parent heterosis, while, the cross P1P8 under normal (63.36%) and under drought condition (68.03%), respectively, were the most superior crosses according to the better parent heterosis.
Regarding ID% in F2, the least decreasing of grain yield/plant was found in the cross P2P5 (3.64% and 5.86%) under normal and drought conditions, respectively.
Three parents showed that they are good combiners according to their values of GCA i.e. Giza-168 (P3) under normal condition, Giza-165 (P8) under drought condition and Sakha-93 (P2) for DSI. As for SCA the 3 crosses, (P5P6 under normal condition, P1P8 under drought condition and P1P3 for F1DSI) confirmed that they are superior in their SCA performance to grain yield/plant.
The estimated genetic parameters showed that both additive and non-additive gene effects are acting as main factors affecting grain yield/plant and that the non-additive effect is greater than the additive effect. Over dominance is involved in controlling this trait in F1 under both conditions as well as DSI in F1 and F2 under both conditions. Partial dominance was detected for DSI in F2. Both F1 and F2 grown under normal and drought conditions showed different types of non-allelic gene interactions. Two types of non-allelic gene interactions were found for grain yield per plant, the duplicate type which appeared in F1 under both conditions and in F2 under normal condition and the complementary type which appeared in F1DSI and in F2 under stress condition. Therefore, the change in the environmental conditions may affect the genetic behavior that gives a great chance for selection for specific environment such as drought stress or salinity.
The values of narrow sense heritability were moderate for DSI in F2 (0.557), relatively low (0.397) for F2 under drought condition and for F2 (0.299) under normal condition or very low for F1 under normal condition (0.072), for DSI in F1 (0.068) and for F1 under drought condition (0.036).
B- Correlation Relationship for Studied Characters:
In the parents and in F1 under normal condition, it is found that all possible combinations between the different pairs of characters are significantly positive correlated. In the parents and F2 positive correlation was found between all pairs of characters except between plant height and number of kernels/spike, which was negative.
In the parents and F1 hybrids, under drought stress condition, it was found that all possible combinations were significantly positive correlated except between number of spikes/plant with number of kernel/spike in which positive correlation was not significant. In the parents and F2 generation 3 out of 10 possible combinations were significantly positive correlated i.e. between grain yield/plant with plant height, and plant height with number of kernel per spike and 1000-kernel weight. The other correlations were only positive.