Physiological and genetic effects of gamma rays, ethylmethane sulphonate, hydrazine, cysteine and their combinations in Sorghum bicolor (L.) Moench

Abstract

Seeds of two varieties of Sorghum bicolor (L.) Moench. Tx-414 and NM-31 were irradiated with 20, 35 and 50 kr of ⁶⁰Co gamma rays at Oak Ridge National Laboratory. Sees of TX-414 also were treated with several concentrations of hydrazine (HZ) and ethylmethane sulphonate (EMS), singly and in combinations, with and without cysteine, used as a pre- and post-treatment modifier. NM-31 was found to be more mutagen sensitive to gamma rays than TX-414, as evidenced by greater reductions in seed germination, primary root length, coleoptile length, seedling height and fertility in the M₁ generation and increases in the frequency of chlorophyll mutations in the M₂ generation. Hydrazine was found to be a highly efficient mutagen based on low seedling injury and seed sterility in the M₁ generation and high frequency of chlorophyll in the M₂ generation. The mean frequencies of viable mutations recovered from HZ, EMS and gamma ray treatments were 2.13%, 0.80% and 0.42% respectively. Combination treatments of gamma +HZ and EMS + HZ or HZ + EMS were found to be highly toxic though a less than additive effect was observed for the reduction in seed germination and seedling injury in the M₁ generation. Fertility reduction was more than additive in HZ+EMS and EMS+HZ treatments while it was less than additive in gamma + HZ treatments..