الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
 |  | from | 115 |  |  |
| | | from | 115 | | |
Abstract
1. Analysis of variance and variance components.
Based on the analysis of variance, data of yield and its components indicate that number of plants/ plot and number of ear/plot, for the different sowing date were significant, while plant height (cm) was non-significant. Sowing date on1st august were superior than other sowing date on plant height, number of plants/ plot. Increasing irrigation levels up to 100 % ET led to an increase in the plant height by 17.53 and 6.40 cm, number of plants/plot by 4.90 and 1.17 and number of ears/ plot by 6.50 and 2.29 compared with irrigation levels from 70 and 85 % ET. Whereas, Single cross 162 excelled significantly in plant height, number of plants/ plot and number of ears/plot compared with other hybrids. The hybrid differences in all the studied traits of maize may be ascribed to the genetically differences among them, which play an important role for exploiting the uptake of the available nutrients and photosynthesis process leading to much noticeable changes of the metabolites accumulated in maize shortage organs. Analysis of variance, data of yield and its components showed that ears weight kg/ plot, ear length (cm) and ear diameter (cm)for the different sowing date were significant. Sowing date on 15thJuly were superior than others sowing date in ear length and ear diameter compared with others sowing date. Increasing irrigation levels up to 100 % ET led to an increase in the ears weight by kg/ plot1.16 and 0.66, ear length by 1.54 and 0.87 cm, ear diameter by 0.30 and 0.31cmcompared with irrigation levels70 and 85
% ET. Single cross 176 superior in ears weight kg/ plot, ear length and ear diameter. The hybrid differences in all the studied traits of maize may be ascribed to the genetically differences among them, which play an important role for exploiting the uptake of the available nutrients and photosynthesis process leading to much noticeable changes of the metabolites accumulated in maize shortage organs.
Data due to analysis of variance, for yield and its components indicate that grain weight /ear (g), ears kg /plot and ears yield ardb/ fed for the different sowing date were significant. Sowing date on 15thJuly were superior than others sowing date in grain weight /ear, ears kg /plot and ears yield compared with others sowing date. Increasing irrigation levels up to 100 % ET led to an increase in the grain weight /ear by 4.85 and 4.89 g, ears weight by 0.70 and 0.40 kg /plot and ears yield by 2.00 and 1.15 ardb/fed, compared with irrigation levels from 70 and 85 % ET. Single cross 176 superior in grain weight /ear, ears weight and ears yield ardb/ fed compared with other hybrids. It is worthy to mention that the differences among the studied hybrids in grain yield may be due to the differences in genetic structure between the four maize hybrids. The hybrid differences in all the studied traits of maize may be ascribed to the genetically differences among them, which play an important role for exploiting the uptake of the available nutrients and photosynthesis process leading to much noticeable changes of the metabolites accumulated in maize shortage organs.
Significant interaction effect between sowing date and irrigation levels on yield and its components. Generally, maize sowing on 1st august and irrigated 70 % ET was the efficient interaction treatment for enhancing plant height and number of plants/ plot. On the ether hand maize sowing on 1st august and irrigated 85 % ET was insignificant with maize sowing on 1st august and irrigated 70 % ET in plant height and number of plants/ plot.
Significant interaction effect between sowing date and irrigation levels on yield and its components. Generally, maize sowing on 1st august and irrigated 70 % ET was the efficient interaction treatment for enhancing ears weight kg/ plot, ear length and ear diameter. On the ether hand maize sowing on 1st august and irrigated 85 % ET was non-significant with maize sowing on 1st august and irrigated 70 % ET in plant height, number of plants/plot, ear length and ear diameter.
Significant interaction effect between sowing date and irrigation levels on yield and its components were shown. Generally, maize sowing on 1st august and irrigated 70 % ET was the efficient interaction treatment for enhancing grain weight /ear, ears kg /plot and ears yield. On the ether hand maize sowing on 1st august and irrigated 85 % ET was non-significant with maize sowing on 1st august and irrigated 70 % ET in plant height, number of plants/ plot, ear length and ear diameter.
Effects of interaction among corn hybrids and irrigation levels for plant height, number of plant/ plot and number of ear / plot. Single cross 162 were achieved the heist values of plant height, number of plants/plot and number of ears/plot under 70 % ET irrigation levels.
Ears weight kg/plot, ear length and ear diameter, were recorded the heist values when the maize single cross 176irrigated with and 85 % ET irrigation levels.
Single cross 162 were achieved the heist values of grain weight /ear under 70 % ET irrigation levels. While ears kg /plot and ears yield were recorded the heist values when the maize single cross 176irrigated with and 85 % ET irrigation levels.
Significant effects on plant height number of plants/ plot. Single cross 162 was sowing on1st July achieved the highest values of plant height, number of plants/plot and number of ears/plot.
significant effects on ears weight kg/ plot, ear length and ear diameter. Single cross 176 was sowing on1stJuly gave the heist values of ears weight kg/ plot and ear length. On the other hand ear diameter was recorded the heist value when single cross 176 sown on 15th July.
significant effects due to grain weight /ear, ears kg /plot and ears yield. Single cross 176 was sowing on1stJuly gave the heist values of grain weight /ear, ears kg /plot and ears yield.
significant differences among means of plant height and number of plants/ plot. The maximum values of plant height was achieved for single cross 176 while single cross 162 was achieved the heist values of number of plants/ plot when plants irrigated by 3500m3 and sown on 1st August.
significant differences ears weight kg/ plot, ear length (cm) and ear diameter (cm).Single cross 162 was achieved the heist values of ears weight kg/ plot when plants irrigated by 3500m3 and sown on 1st August. On the other hand ear weight kg/ plot was recorded the heist values when maize single cross 176irrigated by 100 % ET and sown on 15thJuly. Whereas ear length and ear diameter recorded the heist, values when maize single cross 176 irrigated by 100 % ET and sown on 1stJuly.
significant differences between means of grain weight /ear (g), ear kg/ plot and ear ardb/ feddan . Ears kg /plot and ears yield/fed were recorded the heist values when maize single cross 176irrigated by 100 % ET and sown on 15thJuly.
3. Stress indices for eighteen environments.
Average of ear ardb/ feddan for the eighteen environments irrigation levels(70 % , 85 %and100 % evapotranspiration) through the dates (1stJuly, 15thJuly and 1stAugust) may be reflecting different performances by genotypes, in Table (19) showed that, the best cultivar wasH176 with 18.38 ardb/ feddan. While the second best cultivar was,H168 by 14.18 ardb/ feddan.
3.1 Drought tolerance index (DTI)
Drought tolerance index (DTI) is a value that measures drought tolerance hence, the higher value of DTI is the greater degree of tolerance of a given genotype. DTI at 70 % of irrigation levels environments in Table
(20) manifested that, the best cultivar was H176 recorded 93.46 reflecting that, this cultivar was the best tolerant at harsh environments. While the second-best cultivar was H168 recording 87.96. DTI at 85 % of irrigation
levels environments manifested that, H176 was the best cultivar recording
99.79 reflecting that, this cultivar was the best tolerant at85 % ETof level irrigation from optimum environments. The second best cultivar was h 168 by 93.45. While at the combined DTI, H176 was the best cultivar recorded 96.62, while the best second cultivar was H168 recording 90.71.cleared that, the different genotypes differed greatly in their response to water stress.
3.2 Drought susceptibility index (DSI)
Drought susceptibility index (DSI) is a value that, measures drought sensitivity hence, the smaller value of DSI is the greater degree of tolerance of a given genotype. DSI at 70 % of irrigation levels environments showed that the best cultivar was H176 recorded 0.54 at harsh environments. While the second best cultivars wereH168 recording 1. DSI at 85 % of irrigation levels of environments regarded that, the best cultivar was H176 recorded
0.03 reflecting that, this cultivar was the best tolerant at level irrigation 85
% from optimum environments. While the second best cultivar was H168 with 0.89. H176 was the best cultivar with 0.29 at combined DSI, while the second best cultivar was H168 with 0.94 cleared that, the different genotypes performance differed greatly in their response to drought stress.
3.3. Stress tolerance index (STI)
Stress tolerance index (STI) is a value that, measures drought tolerance hence, the higher value of STI is the greater degree of tolerance of a given genotype. STI at 70 % of irrigation levels environments,the best cultivar was H176 with 1.52 at harsh environments. While the second best cultivar was H168 by0.93. STI at 85 % of irrigation levels environments showed that, the best cultivar was H176 with 1.63. While the second best cultivar was H168 by 0.99 . At combined STI the best cultivar was H176 with 1.58, whilst the second best cultivar was H168 recorded 0.96.the best criterion for determining genotypes that are more resistant to moisture
stress compared to non-stress field environments (normal conditions) with a higher yield is the stress tolerance index.
3.4. Relative performance (P)
Relative performance (P) is a value that, measures drought tolerance hence, the higher value of P is the greater degree of tolerance of a given genotype. P at 70% of irrigation levels environments revealed that the best cultivar was H176 with 1.06 at harsh environments. While the second best cultivar was H168 recording 1.P at 85 % of irrigation levels environments manifested that, the best cultivar was H176 with 1.08.Combined P reported that the best cultivar was H176 with 1.07, whilst the next best cultivar was H168 with 1.01. came to the conclusion resistance indices for harsh environmental conditions compared to optimal conditions, are useful in classifying these genotypes into groups that are associated with specific conditions.
3.5. Geometric mean productivity (GMP)
Geometric mean productivity (GMP) is a value that, measures drought tolerance hence, the higher value of GMP is the greater degree of tolerance of a given genotype.GMP at 70 % of irrigation levels environments in Table (24) showed that, the best cultivar was H176 with
18.17 at harsh environments. While the second-best cultivar was H168 by
14.18. GMP at 85 % of irrigation levels environments manifested that the best cultivar was H 176 with 18.78. While the second-best cultivar was H168 by 14.62. Combined GMP reported that, the best cultivar was H176 with 18.48, whilst the second best cultivar was H168 recorded 14.4.
Many investigators take the same our trend; geometric mean productivity, it could be possible to take advantage of a variety of indices to make categorization of a tested genotypes groups under both drought stress and normal conditions in the form of groups as follows: 1. the first group, the genotypes that give a better yield under non-stress conditions, 2. the second group, the genotypes that give a higher yield under the environmental stress
conditions, 3. the third group, the genotypes that is distinguished in the crop under water stress compared to normal conditions, 4. the fourth group that is medium tolerated under water stress compared to normal conditions, 5. the fifth group, which gave the lowest grain yield under water stress compared to the normal conditions.