الفهرس 
IntroductionOnly 14 pages are availabe for public view
Abstract
The present investigation was carried out to study heterosis and combining ability estimates and their interaction with environments (normal and stress irrigation treatments). The breeding materials used herein included eight parents Ib. 4, Ib.2 , L9 , L22 , Sakha 93, M37, M45 and Giza 168. In the first season 2012/2013, the eight parents were grown at various planting dates in order to overcome differences in time of heading. All possible parental combinations without reciprocals were made among the eight parents. In the second season 2013/2014 the eight parents and their twenty eight possible F1 crosses were sown on 25th Nov. 2013, in RCBD with three replications. The normal irrigation traits (E1) and the second experiment was irrigated once after planting irrigation (E2) (stress). Each plot consisted of one ridge; three meters long with 60 cm between ridges and plants within ridge were 20 cm apart. The dry method of planting was used in this concern, the other cultural practices of growing wheat were properly practiced. Data were recorded on five individual plants randomly sampled from each plot for growth yield and yield components and biological yield/ plant.
The susceptibility index (SI) was calculated for the two experiments from origin data of yield and yield components.
The data obtained for each trait was statistically analyzed. An ordinary analysis of variance was firstly performed for each experiment, and then a combined analysis was carried out whenever homogeneity of error existed.
Heterosis was computed as the percentage deviation of F1 mean performance from either the mid parent (MP) or the better parent mean (BP) for each individual cross. General and specific combining ability estimates were obtained by employing Griffing (1956) diallel cross analysis designated as a method-2 model -1.
The results obtained can be summarized as follows:-
Analysis of variance
Analyses of variance for yield and its components, i.e, plant height, spike length, number of spikes/ plant, 1000-kernel weight, biological yield plant-1, and grain yield plant-1 under drought and normal irrigation as well as combined analysis was carried out.
Genotypes mean squares were significant for all studied traits except No of spike plant-1 in drought environment indicating wide diversity between all genotypes used in this work. Moreover, significant mean squares between genotypes and environment interaction were detected for all studied traits.
Mean squares due to parents were significant or highly significant for all traits in drought stress, normal irrigation and the combined across them except parents mean squares due to No of spikes plant-1 and 1000-kernel weight in the drought environment as well as grain yield plant-1 in normal irrigation environment indicating that these parents are differently in the aforementioned significant traits. Moreover, mean squares due to the interaction between parents and environments were significant for all studied traits except number of spikes/ plant. Such result indicated that wheat parents responded differently to stress and non-stress conditions.