CYTOGENETIC STUDIES OF GAMMA IRRADIATED RICE VARIETIES
Dormant seeds of 3 rice varieties, Colusa (j-aponica), Nato (indica- japonica hybrid), and Rexoro (indica), were exposed to 9 gamma radiation treatments: 20,000, 30,000, 40,000, and 50,000r at 605r/min; 37,100r at 605r/min in 2 equal fractions; 20,480, 37,100, 41,000, and 49,500r at 2.9r/min. R/sub 1/ and R/sub 2/ generation plants from these treatments were studied in 1959 and 1960. Part of the seeds were sown shortly after irradiation and the remainder 1 year later. Effects of irradiation treatments on germination, seedling survival, seedling height, translocation frequency in PMCs, and chlorophyll mutations were studied. The fractionated treatment did not produce any appreciably different effect from that of the comparable continuous treatment. No marked differences in varietal response to different irradiation treatments were noticeable for survival and height. Translocation frequency was slightly lower in Rexoro than in the other varieties. Germination was normal in all of the treatments. Survival appeared normal in all dosages at 605r/min. There was no intensity effect on survival at the 20,000r dose level. With doses approximating 40,000r, a slight reduction was noted for the low intensity. With doses approximating 50,000r, intensity effect was very distinct, with the low intensity treatment showing only 7% survival. Seedling height was progressively reduced with increasing dosages. About 41% of all panicles examined contained 1 or more translocations. Panicles with single hexavalents occurred in greater frequencies than expected, compared to their number with 2 quadrivalents, suggesting a strong tendency for 1 chromosome pair to undergo 2 breaks. Translocation frequency increased with increasing doses up to 40,000r, and then seemed to level off. No chlorophyll mutations were obtained in the R/sub 1/ generation. In the R/sub 2/ generation, 4 types were recognized, albino, xantha, viridis, and variegated. Of these, the variegated types were often variable in appearance and expression. The 225 R/sub 2/ progenies tested gave 42 mutations in 38 progenies, comprised of 21 albino, 6 xantha, and 15 viridis types. Mutation rate increased with increasing dosages. Irradiation by itself did not seem to affect germination and translocation frequency markedly after post-irradiation storage. But it reduced seedling survival at high dosages and low intensities. While irradiation without storage did not affect survival in any of the 605r/min treatments, there was a marked decline with the 50,000r dose following storage. Low intensity irradiation with approximately 20,000r, did not have any different effect on survival after storage than before storage. Following storage, approximately 40,000r, low intensity irradiation caused a severe reduction in survival compared to the same high intensity treatment. (Dissertation Abstr. 23: May 1983)
- Research Organization:
- Originating Research Org. not identified
- NSA Number:
- NSA-17-025004
- OSTI ID:
- 4704512
- Country of Publication:
- Country unknown/Code not available
- Language:
- English
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