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

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 for eitherfission neutrons or 60Co gamma-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, increase linearly for both radiations. The r.b.e. values were greater than1100 at 0.40 sectors per leaf 4 and greater than 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 plus or minus 9; and at 3.0sectors per leaf 5, 118 plus or minus 21. As measured by sectors per krad, mutagenic efficiency increased with increased dose of gamma-radiation; the opposite was true for fission neutrons. This trend was more evident for leaf 4 than for leaf 5.