Differential Radiosensitivity in Rice (Oryza sativa Linn.) at the Genotypic Level

Abstract

INFORMATION on differential radiosensitivity of genotypes of a gene locus is scanty¹. During a course of investigations on the effects of pile radiation on rice, advantage was taken of an anthocyanin pigmented mutant appearing as a heterozygote for albinism in N ₁ population of a variety GEB-24 to study the relative radiosensitivity of the genotypes at this locus. N ₂ seedlings of the mutant segregated into greens and albinos in a 3 : 1 ratio. N ₃ plants, homozygous dominant and heterozygous for chlorophyll character, segregated in 1 : 2 ratio, showing that the genes for albinism behaved as simple recessive to normal green. In the first of the two experiments, dry seeds from the heterozygous N ₁ plant were irradiated with 5–40 kr. of X-rays from a therapy type X-ray machine operating at 250 kV., 30 m.amp., with 2.0 mm. copper. The seeds, stabilized for moisture content, were placed at a distance of 22.0 cm. from the target and at that distance the dose-rate was 309 r. per min. In the second experiment, in addition to those from the N ₁ plant referred to above, seeds of one of its N ₂ progeny, known to be homozygous dominant for green, were also irradiated. The dosage-range was 10–50 kr., and the dose-rate at a distance of 13.5 cm. from the target was 650 r. per min.