Use of Gamma Rays and Hybridization to Create New Drought Tolerant Wheat Genotypes

Abstract

Selection from established high yielding pure line wheat cultivars would rarely isolate a new genotype. Inducing new genetic variation in bread wheat populations via gamma ray irradiation and hybridization procedures and isolating drought tolerant genotypes from derived heterogeneous populations were the aims of this study. The M2 populations of seven irradiated wheat genotypes exhibited differences in the magnitude of   phenotypic (PCV) and genotypic (GCV) coefficient of variation and heritability for studied traits under water stress (WS) and well watering (WW) conditions. The highest expected gain from selection (GA) for grain yield/plant (GYPP) was shown by Sids-4 irradiated (I) and Sakha-61 (I) under well watering (WW) and Aseel-5 (I) and Sids-4 (I) under WS conditions. The predicted GA from selection for GYPP  in the F2’s  of diallel crosses among six genotypes,  reached a maximum of 71.6% under WS for F2 of (As-5 x Sk-93). Selection for high GYPP and other desirable traits was practiced in the M2 and F2 populations under WW and WS. Progenies of these selections (53 M3 and 109 F3 families) and their seven parents were evaluated under WW and WS. Selection under WS was more efficient than that under WW for the use under WS. Twelve families (7 M3’s and 5 F2’s) significantly outyielded their parents by at least 15 % and reached 74.71% for SF9 (a family selected from F2 of Sd-4 x Mr-5) under WS and therefore were considered as putative drought tolerant (DT). These DT genotypes were superior in one or more yield component traits as compared with their parents under drought stress.