X-ray induced Chromosomal Aberrations in Rice Plants

Abstract

Dry and soaked seeds of several varieties of rice plants were irradiated with various degrees of doses at 120KVP, 3mA, distance 26cm., no filter. Results of cytogenetical observation of various sterile plants caused by the chromosomal aberrations were briefly summarized as follows:1. About 68 per cent of the chromosomal aberrations observed was the interchange heterozygote including (4) and (4)+(4), and about 32 per cent was trisomics, asynapsis, syncyte formation and polyploidy.2. The interchange heterozygotes were divided into several types based on the frequencies of ring or chain formation of four chromosomes at diakinesis.3. The fertility (seed or pollen) in the interchange heterozygote rans approximately parallel to the frequency of side-by-side configuration of the interchage complex at metaphase-I.4. Fertility in the progeny of the selfed interchange heterozygote differed from plant to plant, that is, some plants divided into two fertility groups, high and low, and other one showed continuous deviations.5. In the progeny of the selfed interchange heterozygote, plants with RT (interchange heterozygote) and without RT (non-interchange heterozygote) showed the segregation of 1:1 ratio.6. In the same interchange heterozygote, there was such a case showing much difference in distribution of fertility and segregation of the interchange heterozygote.7. Asynapsis and syncyte formation were observed. Especially, the latter is the first example in rice plants.8. Polyploidies, such as haploidy, triploidy and tetraploidy, have also been isolated from the progeny of X-ray irradiated rice plants.