Evaluation of Drought Tolerance in Bread Wheat Advanced Genotypes in Field and Laboratory Conditions

In order to evaluate drought tolerance in some bread wheat genotypes in field and laboratory conditions (germination stage), a research was conducted. Field experiments were carried out in randomized complete block design with three replications in two rain-fed and irrigated conditions. To evaluate drought tolerance at germination stage, a factorial combinations of twenty genotypes and four drought levels (0, -0.4, -0.8 and -1.2 MPa) as a completely randomized design with three replications were conducted in laboratory. At the field experiment significant differences were found among genotypes for grain yield in rain-fed and irrigated conditions. Results of correlation analysis showed that Stress Tolerance Index (STI), Mean Productivity (MP) and Geometric Mean Productivity (GMP) were the best indices for identifying of high yield genotypes in both conditions. Based on drought resistance indices, genotypes No. 18 and 19 were identified as relatively drought tolerant genotypes. In laboratory experiment characters such as germination percentage, germination rate, seed vigor, root length, shoot length and Germination Stress Index (GSI) were evaluated. Results showed that all of these traits decreased when rate of drought stress caused by polyethylene glycol increased. Germination rate was more sensitive to drought than the germination percentage, and shoot length was more sensitive to drought than the root length. Germination vigor was identified as a more sensitive character to drought in compare to the other germination traits. Genotypes No. 2 (Cross Alborz), 6 and 13, were identified as tolerant genotypes in germination stage. Correlation between germination traits in laboratory with STI was not significant. Therefore, based on these results germination traits were not instrumental indicators of drought tolerance in early stages of growth period.