RADIATION-INDUCED MUTATIONS IN WHEAT AND BARLEY

Abstract

The effectiveness of absorbed radiophosphorus for mutation induction in wheat and barley has been studied. The P32was supplied to seedlings and to young plants. Chromosome aberrations found in groups of several cells at meiosis were counted but single cell aberrations were not. Following some dosages of P32, as many as one-third of the treated plants were found to have blocks or clusters of aberrant cells. Samples of R2(progeny of treated) plants of vulgare wheat and of common barley were also examined for the presence of chromosome aberrations at meiosis. The samples consisted of 143 wheat and 128 barley plants. Approximately 8 to 19% of wheat and 6 to 11% of barley plants of different treatment groups had aberrations. Phenotypic mutants were found in barley, einkorn, and vulgare wheat. Chlorophyll mutants occurred in all of these though no albinos were produced in vulgare. The R2and R3of vulgare, consisting of 10,443 plants from 258 treated R1plants, included 15 recognized mutants. The original mutants did not breed true. Offspring of some mutants included only mutant and normal-appearing plants. Other mutants gave a variety of new phenotypic forms; some of these are true-breeding. Nearly all of the wheat mutants gave evidence of chromosome aberrations. Most of the phenotypic changes are therefore attributed to changed gene balance rather than to gene mutation.A few mutations have also been obtained by irradiating wheat and barley seeds with high-energy X rays from the betatron. Two such mutants in wheat were found to have undergone chromosome breakage and rearrangement.