الفهرس 
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Abstract
The present investigation was undertaken at El-Mattana Agricultural Research Station, Agricultural Research Center, Egypt, during three seasons of 2003/2004, 2004/2005 and 2005/2006. The objectives of the present investigation were to study the following aspects:
1-Mean performance, analysis of variance.
2-Estimate the general combining ability and specific combining ability effects.
3-Estimate the Heat susceptibility index.
The studied characters included:
Days to heading, days to physiological maturity, plant height, flag leaf area, duration of grain filling period, grain production rate, number of spikes per plant, number of kernel per plant, 1000-kernel weight, grain yield per plant, straw yield per plant and harvest index.
Six of durum wheat genotypes were used in this study. These genotypes differed widely in their genetic make up namely; (1) Bani-Sweef 1, (2) Sohage 3, (3) Line #1, (4) Line #2, (5) Line #3, (6) Line # 4.
In 2003/2004 season these genotypes were crossed in all possible combinations excluding reciprocals. In 2004/2005 season, further intercrossing among the six parents was performed for more F1-hypbrid seeds.
Both parents and F1 hybrids were sown in season 2005/2006 in tow experiments i.e. the first on 20th November (recommended date) at the second on 20th December (late date) in a randomized complete block design with four replicates. Data were recorded on ten individual plants for studied characters.
Heterosis was estimated as the deviation of F1 mean from mid-parent and better parent values.
The analysis of variance was computed and partitioned into general and specific combining ability . Statistical and genetic analysis were performed as follows:
-Griffing (1956) to estimate general and specific combining ability effects.
-Bahatt (1971) to calculate heterosis over mid-parent and better parent.
-Fischer and Maurer (1978) to estimate heat susceptibility index.
The obtained results can be summarized as follows:
A- Mean performance:
Analysis of variance revealed highly significant differences among genotypes, parents and F1 crosses for all the characters studied under both planting dates.
1- Days to heading: Line #3 and Line #1 were the earliest in the recommended and late planting dates, respectively, while Bani-Sweef 1 the latest under both planting dates. Cross (Line #2 x Line #3) was the earliest under both planting dates, while cross (Sohage3 x Line #1) under both planting dates.
2- Days to physiological maturity: Overall averages decreased as the planting date was delayed. While Line #3 the earliest under both planting dates, and Bani-Sweef 1 the latest under both planting dates. Crosses (Line #3 x Line #4) and (Line #2 x Line #4) were the earliest in the recommended and late planting dates, respectively, while cross (Bani-Sweef 1 x Sohage 3) the latest in the recommended planting date.
3- Plant height: A wide range of plant height was found between different parental lines. For parents Line #2 the tallest and Line #4 the shortest. Cross (Line #1 x Line #2) recorded the tallest plants under both planting dates, while cross (Bani-Sweef 1 x Line #3) recorded the shortest plants under both planting dates.
4- Flag leaf area: Sohage 3 showed the highest value in flag leaf area under both planting dates. Similarly, the cross (Bani-Sweef 1 x Line #2) was the highest value in flag leaf area under both planting dates.
5- Grain filling period: Late planting reduced grain filling period by (29.8 , 30.7 %) for parents and F1 crosses, respectively as compared with the recommended planting date.
6- Grain production rate: Late planting reduced grain production rate when compared with recommended planting date. Cross (Line #1 x Line #2) recorded the highest value in grain production rate under both planting dates.
7- Number of spikes per plant: A wide range of number of spikes per plant was found between different parental lines. Line #2 was the highest in number of spikes per plant under both planting dates. Similarly crosses differed widely in number of spikes per plant.
Susceptibility index values indicated that all the parents were heat tolerant except Sohage3. Tolerant F1 crosses were (P1xP4), (P2xP3) and (P2xP6).
8- Number of kernels per spike: Generally, number of kernels per spike was low in the late planting date compared with the same character in the recommended planting date. Bani-Sweef 1 recorded the highest value in number of kernels per spike under both planting dates. Similarly, crosses widely in number of kernels per spike.
Susceptibility index values showed that the heat tolerant parents were Bani-Sweef 1, Sohage 3, Line #2 and Line #4. The F1 crosses which showed heat tolerance were (P1xP2), (P1xP3), (P1xP5), (P2xP3), (P3xP5), (P3xP6) and (P5xP6).
9- 1000-kernel weight: For parents Line #2 was the highest in 1000-kernel weight under both planting dates. Similarly, crosses (Line #4 x Line #3) and (Line #4 x Line #6) were the highest in 1000-kernel weight in the recommended and late planting dates, respectively. Generally, late planting reduced 1000-kernel weight when compared with recommended planting date.
Susceptibility index values revealed that the heat tolerant parents were Bani-Sweef 1, Sohage 3, Line #3 and Line #4. The most tolerant F1 crosses were (P1xP3), (P1xP4), (P2xP4), (P2xP5), (P3xP4), (P3xP5), (P3xP6) and (P4xP6).
10- Grain yield per plant: Line #2 showed the highest value in grain yield per plant under both planting dates. However, late planting decreased grain yield per plant for both parents and F1 crosses. Crosses (P3 x P4) and (P1x P6) were the highest in grain yield per plant in recommended and late planting dates, respectively.
Susceptibility index values revealed that the heat tolerant parents were Line #1, Line #3 and Line #4. The F1 crosses which heat tolerant were (P1xP3), (P1xP5), (P1xP6), (P2xP3), (P2xP5), (P2xP6) and (P3xP6).
11- Straw yield per plant: Line #2 and recorded the highest value for straw yield per plant in both planting date, while crosses (Line #1 x Line #2) and (Sohage 3 x Line #1) recorded the highest values for straw yield per plant under recommended and late planting dates, respectively.
12- Harvest index: Sohage 3 and Line #4 were the highest in harvest index in the recommended and late planting dates, respectively. While cross (Line #3 x Line #4) was the highest in harvest index under both planting dates.
B:Heterosis:
Results indicated that there were a varied widely differences between crosses for mid-parent and better parent under recommended and late planting date.
1- Days to heading: Crosses (Bani-Sweef 1 x Line #3), (Sohage 3 x Line #2), (Sohage 3 x Line #3) and (Line #3 x Line #4) showed a negative and significant heterosis value for mid-parent in the recommended planting date. While all the crosses for better parent were positive under both planting date.
2- Days to physiological maturity: Cross (Line #2 x Line #4) showed a negative and significant heterosis value for better parent in the recommended planting date.
3-Plant height: Cross (Bani-Sweef 1x Line #3) showed a negative and significant heterosis value for better parent under both planting dates.
4- Flag leaf area: Crosses (Bani-Sweef 1 x Line #2), (Bani-Sweef 1 x Line #3), (Bani-Sweef 1 x Line #4), (Line #1 x Line #2), (Line #1 x Line #3) and (Line #1 x Line #4) showed a positive and significant heterosis value for better parent under both planting date, and cross (Bani-Sweef 1 x Line #1) showed a positive and significant heterosis value for better parent in the recommended planting date.
5- Grain filling period: Crosses (Sohage 3 x Line #1), (Sohage 3 x Line #4), (Line #1 x Line #2) and (Line #2 x Line #4) showed a negative and significant heterosis value for better parent under both planting dates, and crosses (Bani-Sweef 1 x Line #2),(Bani- Sweef 1 x Line #3) and (Line #1 x Line #4) showed a negative and significant heterosis value for better parent in the recommended planting date, while crosses (Sohage 3 x Line #2) and (Line #1 x Line #3) showed a negative and significant heterosis value for better parent in the late planting date.
6- Grain rate production: All the crosses showed a positive and significant heterosis value for better parent under both planting dates except crosses (Sohage 3 x Line #3) and (Sohage 3 x Line #4) in the recommended planting date, and crosses (Bani-Sweef 1 x Sohage 3), (Bani-Sweef 1 x Line #2), (Line #1 x Line #4) and (Line #2 x Line #3) in the late planting date, and cross (Bani- Sweef 1 x Line #3) under both planting date.
7- Number of spikes per plant: Crosses (Sohage 3 x Line #1), (Sohage 3 x Line #2), (Sohage 3 x Line #4), (Line #1 x Line #2), (Line #1 x Line #3), (Line #1 x Line #4), (Line #2 x Line #3), (Line #2 x Line #4) and (Line #3 x Line #4) showed a positive and significant heterosis value for better parent in the recommended planting date.
8- Number of kernels per spike: Crosses (Line #1 x Line #2), (Line #1 x Line #3) and (Line #1 x Line #4) showed a positive and significant heterosis value for better parent under both planting dates, and crosses (Bani-Sweef 1 x Line #4) and ( Sohage 3 x Line #4) showed a positive and significant heterosis value for better parent in the recommended planting date. While cross (Line #3 x Line #4) showed a positive and significant heterosis value for better parent in the late planting date.
9- 1000-kernel weight: Crosses (Bani-Sweef 1 x Line #1), (Bani-Sweef 1 x Line #4), (Sohage 3 x Line #1) and (Sohage 3 x Line #3) showed a positive and significant heterosis value for better parent under both planting dates. Crosses (Bani-Sweef 1 x Sohage 3), (Line #2 x Line #3) and (Line #3 x Line #4) showed a positive and significant heterosis value for better parent in the recommended planting date, while crosses (Line #1 x Line #3) and (Line #1 x Line #4) showed a positive and significant heterosis value for better parent in the late planting date.
10- Grain yield per plant: Crosses (Bani-Sweef 1 x Line #5), (Sohage 3 x Line #1), (Sohage 3 x Line #2), (Line #1 x Line #3), (Line #1 x Line #4), (Line #2 x Line #4) and (Line #3 x Line #4) showed a positive and significant heterosis value for better parent under both planting date. Crosses (Bani-Sweef 1 x Line #2) and (Line #1 x Line #2) showed a positive and significant heterosis value for better parent in the recommended planting date, and crosses (Bani-Sweef 1 x Line #1), (Sohage 3 x Line #3) and (Sohage 3 x Line #4) showed a positive and significant heterosis value for better parent in the late planting date.
11- Straw yield per plant: Crosses (Sohage 3 x Line #1) and (Line#1 x Line #4) showed a positive and significant heterosis value for better parent under both planting dates, and crosses (Bani-Sweef 1 x Sohage 3) and (Line #1 x Line #2) showed a positive and significant heterosis value for better parent in the recommended planting date. While crosses (Bani-Sweef 1 x Line #2), (Sohage 3 x Line #2), (Sohage 3 x Line #4) and (Line #1 x Line #4) showed a positive and significant heterosis value for better parent in the late planting date.
12- Harvest index: Crosses (Bani-Sweef 1 x Line #4), (Line #1 x Line #3) and (Line #3 x Line #4) showed a positive and significant heterosis value for better parent under both planting dates. Crosses (Bani-Sweef 1 x Line #2) and (Line #2 x Line #3) showed a positive and significant heterosis value for better parent in the recommended planting date, and crosses (Bani-Sweef 1 x Sohage 3) (Bani-Sweef 1 x Line #1), (Sohage 3 x Line #3) and (Line #2 x Line #4) showed a positive and significant heterosis value for better parent in the late planting date.
C: Combining ability:
Analysis of variance and general and specific combining ability showed a significant different among parents and F1 crosses for all studied characters under both planting dates. Results indicated that GCA was more than SCA for all studied characters except flag leaf area under both planting dates, and grain yield per plant and harvest index in the late planting date. High GCA/SCA ratio which exceeded than unity were detected for most the studied characters confirm the importance of additive gene effects in the inheritance of these characters.
Results revealed that P vs. C was significant for all studied characters under both planting dates.
I- General combining ability (gi) effects:
Days to heading: Line #2 and Line #3 showed a negative and significant values of (gi) effects under both planting dates.
Days to physiological maturity: Line #2 and Line #3 showed a negative and significant values of (gi) effects under both planting dates, and Line #1 and Line #4 showed a negative and significant values of (gi) effects in the late planting date.
Plant height: Bani-Sweef 1, Line #3 and Line #4 showed a negative and significant values of (gi) effects under both planting dates.
Flag leaf area: Sohage 3 and Line #2 showed a positive and significant values of (gi) effects under both planting dates.
Grain filling period: Line #1 and Line #4 showed a negative and significant values of (gi) effects under both planting dates.
Grain production rate: Line #2 showed a positive and significant values of (gi) effects under both planting date. Sohage 3 showed a positive and significant values of (gi) effects in the late planting date.
Number of spikes per plant: Line #2 and Line #3 showed a positive and significant values of (gi) effects under both planting dates.
Number of kernels per spike: Bani-Sweef 1 showed a positive and significant values of (gi) effects under both planting dates, and Line #1 showed a positive and significant values of (gi) effects in the late planting date.
1000-kernel weight: Line #2 showed a positive and significant values of (gi) effects under both planting dates. Line #1 showed a positive and significant values of (gi) effects in the recommended planting date.
Grain yield per plant: Line #2 showed a positive and significant values of (gi) effects under both planting dates.
Straw yield plant: Line #2 showed a positive and significant values of (gi) effects under both planting dates, and Bani-Sweef 1 and Sohage 3 showed a positive and significant values of (gi) effects under recommended and late planting dates, respectively.
Harvest index: Line #4 showed a positive and significant values of (gi) effects under both planting dates.
From previous results mentioned that Line #2 which showed a significant (gi) effects for 8 characters out of 12 characters.
II- Specific combining ability (Sij)effects:
Days to heading: Cross (Sohage 3 x Line #2) recorded the highest negative and significant values of (Sij) effects in the recommended planting date. Cross (Line #2 x Line #3) obtained the highest negative and significant values of (Sij) effects in the late planting date.
Days to physiological maturity: Cross (Line #2 x Line #4) observed the highest negative and significant values of (Sij) effects in the recommended planting date, and cross (Sohage 3 x Line #4) showed the highest negative and significant values of (Sij) effects in the late planting date.
Plant height: Cross (Bani-Sweef 1 x Line #3) obtained the highest negative and significant values of (Sij) effects under both planting dates.
Flag leaf area: Cross (Bani-Sweef 1 x Line #2) recorded the highest positive and significant values of (Sij) effects under both planting dates.
Grain filling period: Cross (Bani-Sweef 1 x Line #1) observed the highest negative and significant values of (Sij) effects in the recommended planting date. Cross (Line #1 x Line #2) showed the highest negative and significant values of (Sij) effects in the late planting date.
Grain production rate: Cross (Line #1 x Line #2) recorded the highest positive and significant values of (Sij) effects in the recommended planting date, and cross (Line #1 x Line #3) obtained the highest positive and significant values of (Sij) effects in the late planting date.
Number of spikes per plant: Cross (Line #2 x Line #4) showed the highest positive and significant values of (Sij) effects in the recommended planting date, and cross (Line #1 x Line #3) observed the highest positive and significant values of (Sij) effects in the late planting date.
Number of kernels per spike: Cross (Bani-Sweef 1 x Line #4) observed the highest positive and significant values of (Sij) effects in the recommended planting date. Cross (Line #1 x Line #3) obtained the highest positive and significant values of (Sij) effects in the late planting date.
1000-kernel weight: Cross (Bani-Sweef 1 x Line #4) recorded the highest positive and significant values of (Sij) effects in the recommended planting date. Cross (Line #2 x Line #4) showed the highest positive and significant values of (Sij) effects in the late planting date.
Grain yield per plant: Cross (Line #1 x Line #2) showed the highest positive and significant values of (Sij) effects in the recommended planting date. Cross (Bani-Sweef 1 x Line #4) recorded the highest positive and significant values of (Sij) effects in the late planting date.
Straw yield per plant: Cross (Line #1 x Line #2) obtained the highest positive and significant values of (Sij) effects in the recommended planting date, and cross (Sohage 3 x Line #1) observed the highest positive and significant values of (Sij) effects in the late planting date.
Harvest index: Cross (Line #1 x Line #3) showed the highest positive and significant values of (Sij) effects in the recommended planting date. Cross (Sohage 3 x Line #3) recorded the highest positive and significant values of (Sij) effects in the late planting date.