الفهرس 
INTRODUCTION
The importance of wheatOnly 14 pages are availabe for public view
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Abstract
In the present study, divergent selection was performed for flag leaf angle and for 1000-kernel weight in bread wheat (Triticum aestivum L.) under heat-stressed field conditions of a late sowing date.Five F2 populations derived from crosses established between six advanced lines selected for cell membrane thermostability (CMS)in a previous study at Genetics Dept., Faculty of Agriculture, Assiut University, Egypt were used. selection was imposed for each trait separately in 200 spaced plants of each of the five F2 populations in the high and low directions.Direct responses to selection for flag leaf angle and for1000-kernel weight were measured in the F3 descending families of the selected F2 plants against the F3 bulks for each direction under heat-stressed field conditions.Correlated responses to selection for flag leaf angle in grain yield per plant and 1000-kernel weight, as well as correlated response to selection for 1000-kernel weight in grain yield per plantwere also calculated.
The results could be summarized as follow:
1. Positive and highly significant responses to divergent selection for flag leaf angle were obtained in the five populations, which were higher in magnitude in the low direction (averaged 31.41%) than those obtained in the high direction (averaged 22.0%).
2. The realized heritability estimates obtained for flag leaf angle, ranged from 0.40 to 0.66 (averaged 0.53), were similar and corresponded to heritability estimates obtained by the parent-offspring regression, which ranged from 0.41to 0.56 with an average of 0.50, implementing the use of family selection for such trait.
3. Selection for high flag leaf angle produced concurrent positive and significant responses in grain yield per plantin only two populations, with an average of 5.17%, which was lower in magnitude than the averaged correlated responses obtained in grain yield per plantfor lower flag leaf angle in four populations(averaged 8.24%).
4. Positive and significant correlated responses to selection for higher flag leaf angle were obtained in 1000-kernel weight in four populations (averaged 4.03%), which were smaller in magnitude than those obtained for lower flag leaf angle (averaged 9.56%).
5. Positive and highly significant responses to selection for higher 1000-kernel weight were obtained in the five populations (averaged 3.32%), which was smaller in magnitude than those obtained when the selection was practiced for lower 1000-kernel weight in the five populations (averaged 6.87%). These asymmetrical responses could be attributable to the selection differentials that were greater in the low than those obtained in the high direction, or due to the accumulation of deleterious genes reducing 1000-kernel weight.
6. The realized heritability estimatesobtained for 1000-kernel weight, ranged from 0.27 to 0.33 with an average of 0.29,were similar and corresponded to the heritability estimates obtained by the parent-offspring regression (ranged from 0.28 to 0.33, averaged 0.30).
7. Positive and significant correlated responses to selection for 1000-kernel weightwere obtained in grain yield per plant in three of the five populations in the high direction (averaged 17.88%) and in the five populations in the low direction (averaged 21.39%).
8. Flag leaf angle was positively and significantly correlated with grain yield per plant under heat stress in four populations, and with 1000-kernel weight in only two populations. Positive and highly significant correlationswere found between 1000-kernel weight and grain yield under heat stress in the five populations, indicating the important role of 1000-kernel weight as an indirect selection criterion for grain yield improvement under heat stress in wheat.
9. Bulked segregant analysis (BSA) using twelve SSRs markers for flag leaf angle identified three SSR markers, namely Xgwm294-2A; Xbarc113-6A and Xwmc398-6B were able to distinguish between high from low bulks in at least two populations. Three bands specific for high and two specific for low flag leaf angle were generated, and could be used in the future as markers associated with flag leaf angleunder heat stress in wheat.