Mutation breeding tools are the major advantages that mutants with multiple traits chan be ‎idventified (Till et al., 2007; Jain, 2005, 2010). Although mutation is a random event but, some of the ‎specific characteristics which are found in mutationed plants are very desirable. OIn order to obtaining new property ‎character, you need to have a large population for screening for the bemost desired mutants. The mutation ‎frequency rate of spontaneous mutations is rather low and is therefore difficult to usexploit by the plant breeders ‎‎(Jain, 2010). Mutagenesis areis used by physical (e.g. gamma radiation) and chemical (e.g. ethyl ‎methane sulfonate) mutagen treatment of seed crops (Chopra, 2005; Till et al., 2007; Jain, 2010). ‎Short growing seasons and late season heavy rains are the main challenges tof rice cultivation in ‎North of Iran. Thus, the isolation of novel mutants with a higher yield, shorter growing period ‎‎(earlier maturity date) and high grain quality is necessary. Chemical agents can be beneficial ‎since they provide high mutation rates to produce variants for tolerance to biotic/abiotic stress ‎conditions (Jain, 2010). The dose assessment for chemicals is characterized by altering the ‎duration and concentration of treatment,; the solvent used (e.g. dimethyl sulfoxide),; or the pH of ‎the solution (Jain, 2005). Gohar is a high yielding variety with slender grains and good cooking ‎quality. The variety is late in maturing, requiring a growing period of 135 to 140 days (seed to ‎seed) under local conditions. Therefore, it is of particular importance to improve the variety in ‎order to thus havinge early maturing varieties with a growing period of less than 115 days (seed to ‎seed). The aim of this work has been to select new lines of rice (Gohar variety) that are high ‎yielding, early maturing and with good grain cooking quality.‎