Response to Drought Stress of Two Strawberry Cultivars (cv. Kurdistan and Selva)

In order to evaluate the effect of different levels of drought stress on some physiological parameters in strawberry. one experiment with potted strawberry cultivars 'Kurdistan' and 'Selva' was conducted in summer 2008. The experiment was performed with four drought stress treatments [control (75% of field capacity). SI: mild drought stress (50% of field capacity). S2: severe drought stress (25% of field capacity) and R: one day tiller rewatering]. Physiological parameters such as: leaf relative water content (RWC). membrane stability index (MSI). net CO2 assimilation rate (A), stomatal conductance (g(s)). transpiration (E), water use efficiency (A/g(s)), chlorophyll, proline and soluble carbohydrate contents were measured in leaves of strawberry subjected to different drought stress conditions as well as one day alter rewatering. The results showed that RWC, MSI, A, g, E, and chlorophyll of two cultivars decreased as soil water content was reduced. A/g, was highest under mild water stress for both cultivars. 'Kurdistan' had lower A, g, and E than 'Selva'. RWC. MSI and A/g, of 'Kurdistan' were higher than 'Selva'. Recovery of these parameters was faster for 'Kurdistan than 'Selva'. Chlorophyll contents of 'Kurdistan' was higher than 'Selva'. Chlorophyll recovery didn't occur one day after rewatering. Amount of proline and soluble carbohydrates increased under severe drought stress. 'Kurdistan' had higher proline content compared to 'Selva' under severe drought stress. Amount of prolific and soluble carbohydrates were reduced in both the cultivars one day after rewatering. This study revealed that moderate drought stress affects gas exchange while severe drought stress affects chlorophyll. proline and soluble carbohydrates levels.