Maximum r.b.e. of fission neutrons for induction of somatic mutations in maize

Summary This investigation was conducted to determine the maximum r.b.e. of fission neutrons for the induction of yellow-green sectors in maize. Seeds heterozygous for the yg2 locus were adjusted to 13 per cent water content, irradiated with varying doses of either fission neutrons or 60Co γ-radiation, and soaked for 2 hours in nitrogen-bubbled water at ambient temperature before planting. Frequency of yg2 sectors, as scored in leaves 4 and 5, increased linearly for both radiations. The r.b.e. values were > 1100 at 0·40 sectors per leaf 4 and > 600 at 0·20 sectors per leaf 5; however, at these low frequencies, the standard errors were ∼ 3 times greater than the r.b.e. At 6·0 sectors per leaf 4, the r.b.e. values were 111 ± 9; and at 3·0 sectors per leaf 5, 118 ± 21. As measured by sectors per krad, mutagenic efficiency increased with increased dose of γ-radiation; the opposite was true for fission neutrons. This trend was more evident for leaf 4 than for leaf 5.