Reciprocal translocations induced by x-rays and thermo-neutrons in wild Sorghum (S. purpureo-sericeum Aschers and Schweinf.).

Abstract

Dry seeds of S. purpureo-sericeum were irradiated with either X-rays or thermo-neutrons with three exposures each. No difference was shown in germination between the irradiated treatments and the control. The percentage of survival was greatly reduced to 2.2% in seeds treated with X-rays. However, there was no significant difference in survival between the thermo-neutron treatments and the control. Both radiation treatments inhibited seedling height to a considerable degree, and the variability of seedling height increased with higher exposures of irradiation. The types and the frequency of induced interchanges were proportional to the exposure of thermo-neutron irradiations.Twenty six translocation heterozygous plants were analyzed and considered to be semisterile plants. Spore quartet analysis revealed that the two types of adjacent segregations occur with nearly the same frequency.Six plants with pseudo-isochromosomes were detected. Pseudo-isochromosomes were often delayed in anaphase movement. They were excluded from daughter nuclei at telophase stages and eventually became micronuclei in the spore quartets.Two plants with a ring-of-six, and one plant with two pseudo-isochromosomes plus a ring-of-six were also found among the materials irradiated with high exposures of thermo-neutrons. Pollen counts showed that they had the lowest fertility among translocation heterozygous plants and no seed was obtained.