Non-basmati aromatic rice is very popular for its excellent grain quality with an inbuilt aroma. But these cultivars have been ignored in the mainstream industrial agriculture due to low yielder. It is a serious matter that most of these cultivars are fast disappearing from cultivation in the locality. Therefore, there is an urgent need to improve these cultivars. Mutation breeding is one of the options to improve/rectify of specific traits of these cultivars within a very short period without altering the in-built quality traits viz. aroma. The prime objectives of the experiment were to determine radiation effects and to estimate the optimal dose which was necessary for any mutagenesis-based breeding programme. Popular cultivars namely Badshabhog, Bahadurbhog and Blackjoha were taken for gamma irradiation ranging from 200Gy to 400Gy with an interval of 50Gy and unexposed treatment used as control. The experiment was designed at in vitro and in vivo condition in a randomized block design with three replications. Data were analyzed through Duncan’s test and regression analysis. Most of the traits of each cultivar were exhibited a drastic reduction with increasing doses of gamma rays. The optimal dose of gamma rays based on the weighted mean of LD50 and GR30/GR50 with 40% and 10% weighted, respectively under in vitro and in vivo conditions were estimated at 358.37Gy & 346.10Gy in Badshabhog; 331.19Gy & 319.17Gy in Bahadurbhog; 314.55Gy & 314.05Gy in Blackjoha. This optimum dose of gamma rays can be used for obtaining desirable mutants of these cultivars with minimal damages. Blackjoha had the highest radio-sensitivity while Badshabhog showed relatively tolerant.