This study was carried out during the period from 2004/05 to 2006/07 growing seasons, at Faculty of Agriculture, Sohag University, Egypt to estimate observed and expected response to selection and other genetic parameters and calculate drought susceptibility index. Results re-vealed highly significant differ-ences between F3 and F4 families under normal and drought condi-tions for days to heading, spike length, no. of spikes/plant, no. of kernels/spike, 100-kernel weight and grain yield/plant.
Observed direct response to selection for days to heading was negative and highly significant compared with bulk and the check cultivar in F4 with values of -5.58 and - 13.88 % and -6.13 and -13.88 % under normal and drought conditions, respectively. The expected response to selec-tion was 3.15 and 3.68% under normal and drought conditions, respectively. Observed direct response to selection for grain yield/plant was positive and highly significant compared with bulk, better parent and the check in F4 with values of 28.19, 18.59 and 26.09 % and 27.49, 16.67 and 21.20 % under normal and water stress conditions, respec-tively. On the other hand, the expected response to selection was 11.98 and 9.06% under nor-mal and drought conditions, re-spectively.
Phenotypic and genotypic coefficients of variation under normal conditions for days to heading of the early families were 4.75 and 4.26% in F3 and 5.17 and 4.84% in F4 generation, respectively. While under drought stress conditions those values were 4.26 and 4.05% in F3 and 4.84 and 4.78% in F4 genera-tion, respectively. Phenotypic coefficient of variation for grain yield of the highest yielding families under favourable condi-tions was 14.57 and 13.40 % in F3 and F4 generations, respec-tively, while, it was 13.32 and 12.43 % in the same generations, respectively under water stress conditions. Likewise the genotypic coeffi-cient of variability under normal conditions was 12.48 and 11.96 % in F3 and F4 generations, re-spectively. Meanwhile, it was 10.82 and 10.89 % under drought stress conditions in the two gen-erations, respectively.
High broad sense heritability values for days to heading of the early families was obtained under normal and drought stress in F3 and F4 generations. While narrow sense heritability was 34.34 and 39.40 % in F4 generation under normal and drought stress, re-spectively. The broad sense heritability for grain yield/plant of the highest yielding families was high under normal and water stress in F3 and F4 generation, while, the narrow sense heritabil-ity was 53.34 and 43.43 % in F4 generation under the two studied conditions, respectively. These results showed that the pedigree method of selection was effective to produce new lines tolerant to drought stress with high grain yield.
Drought susceptibility index showed that the nine families, i.e., no. 19, 22, 24, 25, 33, 35, 37, 38 and 39 produced relatively high grain yield under drought stress environments due to high yield potential, rather than having low susceptibility to stress envi-ronments. These genotypes could be used as source of drought tol-erance/or factors contributing to general adaptation.