Evaluation of Drought Stress on Chlorophyll and Proline Traits in Soybean Genotypes

Soybean (Glycine max) is sensitive to drought stress, and increasing its yield, requires the selection of tolerate varieties which are adapted to semiarid or low water climates of Iran. In this research, the experiment was performed based on a factorial completely randomized design with three replications at 2013. Experimental factors were consisted of 8 genotypes of soybeans and 6 levels of drought stress ( irrigation in all growth stages as control treatment, intense stress in vegetative growth stage, intense stress in flowering stage, intense stress in pod stage, intense stress in flowering stage and pod stage and mild stress at all growth stages). The results showed that the drought stress significantly reduced the chlorophyll photosynthetic pigment (including chlorophyll a, b and total) and significantly increased the proline in different treatments so that, the control factor (irrigation in all growth stages) had the highest total chlorophyll (μ= 0.350), a (μ= 0.250) and b (μ= 0.100) and also it had the lowest level in control treatment namely proline (μ= 0.032). Mild Drought stress at all stages of growth and also severe drought stress from start flowering to finish pod levels had the lowest total chlorophyll (μ= 0.23), a (μ= 0.170) and b (μ= 0.060) and also, it had the highest proline (μ= 0.140). Comparison of means of chlorophyll and proline traits under the drought stress showed that genotypes 032 and HillCE were tolerant and genotypes Ford and Sahar were sensitive.