Evaluation of Drought Tolerance of Some Soybean Cultivars

In order to evaluate drought tolerance of some genotypes of indeterminite soybean in Uromia, a field experiment using randomized complete block  design with split plots was conducted in three replications at Research Farm of Uromia Agricultural High School during 2012. The main plots were allocated to three levels of drought stress including: no tension i.e. irigation after every 60 mm evaporation from Class A pan; moderate drought stress with irrigation after 110 mm evaporation and severe drought stress, irrigation after 160 mm evapration). Also, three soybean genotypes (Clark, Wiliyams, and Anion) were planted in the sub-plots. Five drought tolerance indices including stress susceptibility index (SSI), stress tolerance index (STI), tolerance index (TOL), Mean Productivity (MP) and geometric mean productivity index (GMP) were calculated based on grain yield in normal and stress conditions. Stress intensity (SI) for mild and severe stress was, respectively, 0.44 and 0.62. The lowest indexes of SSI and TOL in both stress conditions was related to the genotype Williams. Under irrigation after 160 mm evaporation and based on MP, GMP, and STI indices, genotype Williams had the lowest rank and was sensitive to drought stress. In this experiment, under mild and severe drought stress conditions, genotype Anion had the highest MP, GMP, and STI indices, therefore,  it was recognized as drought tolerant compared with the other genotypes.