Abstract
Drought stress, which significantly affects growth and reduces grain yield, is one of the main problems for wheat crops. Producing promising drought-tolerant wheat cultivars with high yields is one of the main targets for wheat breeders. In this study, a total of seven drought-tolerant wheat genotypes were screened for the presence of 19 specific drought tolerance genes. The genotypes were tested under normal and drought conditions for two growing seasons. Four spike traits, namely, spike length (SPL), grain number per spike (GNPS), number of spikelets per spike (NSPS), and grain yield per spike (GYPS), were scored. The results revealed that drought stress decreased the SPL, GNPS, NSPS, and GYPS, with ranges ranging from 2.14 (NSPS) to 13.92% (GNPS) and from 2.40 (NSPS) to 11.09% (GYPS) in the first and second seasons, respectively. ANOVA revealed high genetic variation among the genotypes for each trait under each treatment. According to the drought tolerance indices, Omara 007 presented the highest level of drought tolerance (average of sum ranks = 3), whereas both Giza-36 genotypes presented the lowest level of drought tolerance (average of sum ranks = 4.8) among the genotypes tested. Among the 19 genes tested, 11 were polymorphic among the selected genotypes. Omara 007 and Omara 002 presented the greatest number of specific drought tolerance genes (nine) tested in this study, whereas Sohag-5, Giza-36, and PI469072 presented the lowest number of drought tolerance genes (four). The number of different genes between each pair of genotypes was calculated. Seven different genes were found between Omara 007 and Giza-36, Omara 007 and Sohag-5, and Omara 002 and PI469072. The results of this study may help to identify the best genotypes for crossing candidate genotypes, and not merely to genetically improve drought tolerance in wheat.