Effectiveness of fission neutrons versus gamma radiation for inducing somatic mutations in presoaked seeds of maize

Abstract

This study was conducted to determine the effectiveness of fission neutrons versus 60Co γ-radiation for inducing somatic mutations in germinating maize embryos. Seeds heterozygous for the yg 2 locus were soaked for 96 h at 20°C prior to irradiation with various doses of either 60Co γ-radiation or fission neutrons. Mitotic index and cytophotometric studies of the shoot (excluding the coleoptile and first 3 leaves) revealed that 33.2, 16.4, 39.5, and 6.1% of the cells were in G 1, S, G 2, and M stages of the cell cycle, respectively. The frequency of yg 2 sectors, as scored in leaves 4 and 5, increased with increasing dose of both radiations. Mutagenic effectiveness, as measured by sectors per rad, increased with increasing dose of γ-radiation but decreased with increasing dose of fission neutrons. This phenomenon resulted in a decrease in relative biological effectiveness (RBE) of fission neutrons with increasing sector frequency. The high mutation frequency, especially at low neutron doses, indicates a potential value of the test system for monitoring genetic effects of low radiation doses and other mutagenic agents.