الفهرس 
INTRODUCTION
Performance of bread wheat genotypes under drought stressOnly 14 pages are availabe for public view
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Abstract
Laboratories and field experiments were carried out at the Agriculture Experimental Research Farm of the Faculty of Agriculture, Assiut University, in the seasons of 2011/2012 and 2012/2013. This work aims to evaluate 30 new wheat genotypes (Triticum aestivum L.) and the two check cultivars, namely, Giza 168 and Sakha 93 under drought and salinity conditions. In each season, two experiments were conducted at the Exp. Farm, Fac. of Agric, Assiut Univ. In the first experiment, the irrigation was applied as needed (normal) while in the second experiment the two first irrigations only were applied (drought). In all experiments a randomized complete block design with four replications was used in the two seasons. Also, the above mentioned genotypes were evaluated for salinity tolerance in the seedling stage.
The results obtained from the evaluation experiments are summarized in the following:
A- Performance of bread wheat genotypes:
Separate analysis of variance for each experiment in each year revealed highly significant differences between the evaluated wheat genotypes in all studied traits.
Combined analysis of variance for the studied traits over the two season under normal irrigation and drought stress. Showed that mean squares due to years were highly significant for all studied traits under both environments except spike length, no. of kernels/spike and 1000-kernel weight under drought stress which were insignificant. Mean squares due genotypes were highly significant for all studied traits under both environments. Mean squares due to G x Y interaction was statistically significant for all traits except spike length under both environments. Combined analysis of variance over all the two seasons and environments. Revealed that mean squares due to years were highly significant for all studied traits except spike length, no. of kernels/spike and 1000-kernel weight.
1- Days to heading:
- Drought stress caused slight decrease in number of days to heading due to water stress in the first, second seasons and th combined by 6.23, 7.75 and 6.97% respectively, compared to normal irrigation condition.
- The earlier genotypes over all seasons and irrigation treatments were Assiut 238, Assiut 241, Mubark, Assiut 249, Assiut 406, Assiut 704, MK 1-1, MK 1-10 and Assiut 401.
2- Plant height:
- The reduction in plant height due to water stress in the first, second seasons and combined means were 8.96, 8.87 and 8.91% compared to normal irrigation condition, respectively.
- The tallest genotypes were Assiut 228 and Assiut401 and shortest were Assiut 224, MK 2-27 and MK 7-81.
3- Spike length:
- The reduction in spike length due to water stress in the first, second seasons and combined means were 4.83, 5.32 and 5.04% compared to normal irrigation condition, respectively.
- The new genotypes, i.e. Assiut224, Assiut248, Assiut249, Assiut724, Assiut725, Assiut726, Assiut733, Sel. 542, MK 1-20, MK 2-27, MK 2-29, MK 7-81 and MK 7-83 gave highly significantly long spikes compared to Giza 168 over all irrigation treatments and seasons.
4- No. of spikes/plant:
- The reduction in no. of spikes/plant due to water stress in the first, second seasons and combined means were 17.94, 18.64 and 18.38% compared to normal irrigation condition, respectively.
- The new genotypes, i.e. Assiut216, Assiut217, Assiut238, Assiut228, Assiut401and R80 were highly significantly surpassed the check cultivar G.168 in no. of spikes/plant.
5- No. of grains/spike:
- The reduction in no. of grains/spike due to water stress in the first, second seasons and combined means were 9.29, 9.51 and 9.40% respectively, compared to normal irrigation condition.
- The new genotypes over all seasons and irrigation treatments, i.e., Assiut224, Assiut406, Assiut228, Assiut724, Assiut726, MK 1-20, MK 2-27, MK 2-29, MK 7-81, MK 7-83 and F6118 highly significantly surpassed the check cultivar G.168 in no. of grains/spike.
6- Grain weight/spike:
- The reductions in grain weight/spike due to water stress in the first, second seasons and combined means were 15.63, 16.81 and 16.18% compared to normal irrigation condition, respectively.
- The new genotypes over all seasons and stress treatments, i.e., Assiut 224, Assiut 228, Assiut 724, Assiut 725, Assiut 726, MK1-20, MK2-27, MK2-29, MK7-81 and MK7-83 highly significantly surpassed G.168.
7- 1000-kernel weight:
- The reductions in 1000-grain weight due to water stress in the first, second seasons and combined means were 10.55, 11.76 and 11.15% compared to normal irrigation condition, respectively.
- Twenty two new genotypes over all seasons and irrigation treatments highly significantly surpassed the check cultivar Sakha 93 in 1000- kernel weight.
8- Grain yield/plant:
- The reductions in grain yield/plant due to water stress in the first, second seasons and combined means were 25.71, 24.48 and 25.07% compared to normal irrigation condition, respectively.
- The results showed that the new tested genotypes, i.e., Assiut216, Assiut 238, Assiut 228, Assiut 726, Assiut 401 and R 80 gave high significantly grain yield compared to the two checks over all seasons and water treatments.
9-Grain yield/plot:
- The reductions in grain yield/plot due to water stress in the first, second seasons and combined means were 19.30, 20.34 and 19.78% compared to normal irrigation condition, respectively.
- The new genotypes Assiut 216, Assiut 228, Assiut 401, R 80 and F6118 highly significantly surpassed the two check cultivars in grain yield/plant.
B- Drought susceptibility index:
1- Grain yield/plant:
- In 2011/2012 season, drought susceptibility index (DSI) ranged from 0.39 for Assiut 704 to 1.70 for Mubarak. The new genotypes, Assiut 108, Assiut224, Assiut 230, Assiut 249 and Assiut 704 showed DSI less than 0.67, so these genotypes are considered to be highly tolerant to drought. The genotypes, Assiut 248, Assiut 406, MK 2-27, MK 7-81and R 80 showed DSI less than 0.87, so these genotypes are considered to be tolerant to drought stress.
- In 2012/2013 season, drought susceptibility index (DSI) ranged from 0.41 for MK 2-27 to 1.73 for Sel. 542. The new genotypes, Assiut217, Assiut224, Assiut 248, Assiut 249, MK 2-27 and MK 2-29 showed DSI less than 0.69, so these genotypes are considered highly tolerant to drought. The genotypes, Assiut 238, Assiut 241, Assiut 406, MK 7-83, and F6118 showed DSI less than 0.88, so these genotypes are considered to be tolerant to drought stress.
- The new genotypes, Assiut224, Assiut248, Assiut 249, Assiut 406, Assiut 704 and MK 2-27 considered to be tolerant to water stress and could be used in wheat breading programms.
2- 1000-kernel weight:
- In the first season, drought susceptibility index (DSI) ranged from 0.49 for MK 2-29 to 1.50 for Assiut 224. The new genotypes, Assiut 108, Assiut725, Sel. 542, MK 2-29 and MK 7-81 showed DSI less than 0.61, so these genotypes are considered highly tolerant to drought. The genotypes, Assiut 228, Mubarak, MK 1-1, MK 7-15, Assiut 401 and F6118 showed DSI less than 0.82, so these genotypes are considered tolerant to drought stress.
- In the second season, drought susceptibility index (DSI) ranged from 0.57 for Sel. 542 to 1.37 for Assiut224. The new genotypes, Assiut108, Assiut725, Mubarak, Sel. 542, MK 2-29 and MK 7-81 showed DSI less than 0.69, so these genotypes are considered highly tolerant to drought. The genotypes, Assiut 228, MK 1-1, MK 7-15, R 80 and F6118 showed DSI less than 0.78, so these genotypes are considered tolerant to drought stress.
- The new genotypes, Assiut108, Assiut228, Assiut 725, Mubarak, MK 1-1, MK 7-15, Sel. 542, MK 2-29, MK 7-81 and F6118 are considered tolerant to water stress and could be used in wheat breading programms.
C- Evaluation of bread wheat genotypes for salinity stress:
- Analysis of variance revealed highly significant differences among genotypes, salinity and GxS interaction.
- The germination power percentage, germination percentage and speed of germination index were decreased with increasing salinity levels. The inhibitory effect was more obvious at the higher level of salinity compared with control. Wheat genotypes, Assiut 217, Assiut 230, Assiut 249, Assiut 228, Sel. 542, MK 1-20, MK 2-27 and MK 2-29 were the most tolerant for the highest level of salinity.
D- Correlation studies:
- In 2011/2012 season, correlation coefficients among the studied traits under normal irrigation and water stress conditions were estimated grain yield/plant was positively and significantly correlated with each of of plant height, no. of spikes/plant, no. of grains/spike, grain weight/spike, 1000-grain weight and grain yield/plot under both environments except 1000-grain weight under drought stress.
- In 2012/2013 season, correlation coefficients among the studied traits under normal irrigation and water stress conditions were recorded grain yield/plant was positively and significantly correlated with each of of plant height, no. of spikes/plant, no. of grains/spike, grain weight/spike, 1000-grain weight and grain yield/plot under both environments, while negatively and significantly with 1000-grain weight under both environments.