Drought is one of the major environmental stresses which greatly affect the plant growth and productivity. In the present study, various doses (0-75 Gy) of gamma rays were applied to investigate the effect of radiation on shoot tip explants. It was observed that the regeneration rates and plant fresh weights decreased significantly with an increase in radiation dose. The optimal irradiation doses for mutation induction were determined at 15 and 20 Gy. Afterwards, the induction of somatic mutation in sugar beet (Beta vulgaris L) was investigated by irradiation of shoot tips with 15 and 20 Gy gamma rays. Irradiated shoot tips were sub-cultured and M1V1-M1V3 generations were obtained. Mutants tolerant to drought stress were selected on MS medium, supplemented with 10 and 20 gl(-1) PEG6000. Of the M1V3 plantlets, drought-tolerant mutants were selected. Leaf soluble proteins obtained from the control and drought-tolerant mutants were analyzed by SDS-PAGE. A total of 22 protein bands were determined and 2 of them were observed to be drought-tolerant mutants except the control. Polymorphism was also detected among the control and drought-tolerant mutants by DNA fingerprinting using ISSR markers. A total of 106 PCR fragments were amplified with 19 ISSR primers and 91 of them were polymorphic. The dendrograms were separated into two main clusters. First cluster included M8 mutant plant, which was applied 20 Gy gamma radiation and regenerated on selective culture media containing 10 gl(-1) PEG6000 concentration, and the second cluster was further divided into five sub-clusters. (C) 2012 Elsevier B.V. All rights reserved.