RESUMO
In an attempt to develop drought tolerant genotypes of bread wheat, two procedures, i.e., mutation and hybridization were used to induce new genetic variation. Selection for high grain yield/plant (GYPP) and other desirable traits was practiced in the M2 populations of 7 gamma irradiated genotypes and F2 populations of 15 diallel crosses among 6 genotypes of wheat under well watering (WW) and water stress (WS) conditions. Progenies of these selections (53 M3 and 109 F3 families) and their seven parents were evaluated in the field under WW and WS. Significant yield superiority of twelve families (7 M3 ’s and 5 F2 ’s) over their original and better parents, respectively under WS reached 74.71% (SF9). These putative drought tolerant families were assessed on the DNA level using SSR analysis. Fifteen SSR primers were used for PCR amplification of the genomic DNA of these 12 selections and their parents. The SSR analysis proved that the 12 families are genetically different from their 7 parents, with an average polymorphism of 86.67%. The genetic similarities (Gs) ranged from 30% to 88%. Both mutants SF3 and SF4 exhibited very low Gs (42 and 40%, respectively) with their common parent (Giza-168), indicating that gamma rays were very effective in changing the genetic background of Giza-168 towards high GYPP under WS conditions. SSR assay permitted the identification of seven unique bands (5 positive and 2 negative) for three drought tolerant wheat genotypes (SF3, SF4 and Aseel-5). These bands might be considered useful as markers associated with drought tolerance in bread wheat breeding programs.