DNA isolation was carried out as per the standard protocol (Khan et al., 2007). The fresh root samples of germinated seedlings were homogenized in mortar and pestle using liquid nitrogen. The freeze dried powder was transferred to sterile micro-centrifuge tubes and 4 ml of extraction buffer [CTAB 3% (w/v), Tris–HCl 100 mM, NaCl 2 M, EDTA 25 mM, β-mercaptoethanol 4%, PVP 5% (w/v)] was added. Tubes were kept in water bath at 70 °C for 30 min. Chloroform:isoamylalcohol (24:1) was added to the mixture and centrifuged at 8000×g for 10 min at 25 °C. The aqueous phase was transferred in fresh tube to which 0.6 volumes of ice-cold isopropanol was added for the precipitation of DNA and was stored at −20 °C for 30 min. The precipitated DNA was centrifuged at 8000×g for 10 min at 4 °C. The supernatant was discarded and the pellet was washed with 80% ethanol twice and dried at room temperature for 15 min. The DNA pellet was dissolved 30 µl of TE RNase.