X-Ray-Induced Reciprocal Translocations and Chlorophyll Mutations in Rice

Abstract

1. Presoaked grains of rice (variety Tjeremas of the indica type of Oryza sativa L.) were exposed to X-ray at a dosage of 4000 r. In a total of twenty-eight surviving plants grown from these grains, four plants were found with a heterozygous reciprocal translocation. 2. Although the height of X2 seedlings was only 23% that of the controls at 30 days, the plants were of equal height at maturity. 3. All the heterozygous reciprocal translocations appeared as a ring or chain of 4 chromosomes or only bivalents at metaphase I. There was apparently no directed orientation, since the alternate and adjacent types occurred with approximately equal frequencies. 4. The types of chlorophyll mutations in the order of their importance were: viridis, albina, xantha, and striata. The frequency of mutation was increased by X-ray approximately twenty times over the spontaneous rate. 5. Low seed-set proved to be a useful criterion for determining the occurrence of a heterozygous reciprocal translocation in the absence of cyt...