Assessment on cytotoxic and mutagenic potency of Gamma rays and EMS in Vigna mungo L. Hepper

To determine the mutagen agent potency and deduce an optimum dose, cytological analysis for induced chromosomal aberrations is considered as an accurate index in mutation breeding. Therefore, the present investigation was carried out to estimate the relative frequency and spectrum of meiotic abnormalities at various stages of cell division using Gamma rays, EMS and their combination treatments in M1 generation of black gram (Vigna mungo L. Hepper) varieties Pant U-30 and T-9. The analysis of M1 plants revealed a wide range of induced meiotic abnormalities like univalents, multivalents, laggards, chromatin bridges, micronuclei and chromosome stickiness by different mutagen doses. In addition to these, behavioral changes like precocious separation of chromosomes at metaphase, unequal separation of bivalents at anaphase, disturbed polarity and cytomixis at telophase were observed at low frequency. A linear relationship between the frequency of chromosomal aberrations and the strength of mutagen doses was observed in both the varieties and mutagen types. It was found that the combined treatments induced meiotic abnormalities at a higher frequency as compared to individual treatments of Gamma rays and EMS. Comparative estimation of induced cytological abnormalities suggested higher mutagenic sensitivity of var. Pant U-30 than the var. T-9 towards the treatments used. This also confirmed the relatively broader genetic tolerance level of black gram var. T-9 in inducing a significant amount of viable mutations without much lethality at the mutagen doses recommended in this study. Therefore, it can be concluded that the combine treatments of Gamma rays and EMS (300Gy+0.2%, 200Gy+0.3%) are relatively more effective for induction mutations in var. T-9 at the genotypic tolerable level.