Mutations in quantitatively inherited traits induced by neutron irradiation

Abstract

The majority of studies involving quantitatively inherited variability induced by neutrons have been made with thermal neutrons and have been associated with attempts to select useful mutants in self-fertilizing species of plants. Neutrons induced similar amounts and types of variability to that induced by low LET radiations. In comparison with efficient chemical mutagens, neutrons induced somewhat less variability and there were some suggestions of mutagen specificity. The results currently available indicate that neutrons induce variation in quantitatively inherited traits and that economically useful mutants can be selected. In the absence of conclusive evidence regarding qualitative and quantitative differences from other mutagens, neutrons should be included in future experiments. The differences in quantitatively inherited variability induced by different mutagens did not parallel the large differences that are observed when chromosomal and gross mutagenic changes are recorded. This is probably a consequence of the additional selection which is imposed before quantitatively inherited variability is studied. Attempts to determine the nature of the genetic changes induced by neutrons have not been conclusive. Genetic correlations and RBE values suggest that the changes leading to quantitatively inherited variability are predominantly chromosomal rather than genic. Further studies on quantitatively inherited systems, particularly with fast neutrons where the problems of dosimetry are simpler, and experiments designed to establish RBE values for single gene mutations in microorganisms should add to knowledge of the nature of the genetic events contributing to quantitatively inherited variation.