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China National Rice Research Institute, hangzhou, Zhenjiang, China
Radiation treatment was applied at different dosages to the germinating
embryos, calli, calli with green spots and calli with developing shoots.
Results indicated that:
1) The callus induction percentage decreased with the increase of the radiation dosage given to germinating embryos. The callus induction frequency was 53.1%, 40.7% and 37.5% for 2.5, 5.0 and 10.0 KR dosage treatment respectively, while that of the CK (without radiation treatment) was 57.4%.
2) The effect of radiation on redifferentiation frequency and on green plantlet regeneration from treated callus varied with different treatment dates as follows: Callus treatment>treatment of callus with green spots>treatment of callus with developing shoots>treatment of germinating embryos.
3) In-vitro radiation treatment reduced the fertility of regenerated plants but was able to increase their stigma exertion rate, and the frequency of early maturing plants in their progenies (Tables 1 and 2).
It is suggested that the low dosage radiation treatment (2.5-5.0 KR) to callus
with green spots are worthy of adoption in rice improvement.
Table 1. Effect of gamma-ray radiation on the fertility and stigma
exsertion of regenerated plants
Table 2. Effect of gamma-ray radiation on the percentage of early-maturing
lines in T2 progenies of regenerated rice plants
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In-vitro radiation dosage (KR) Basmati 370
=============================== selection
0 2.5 5.0 10.0
Number of lines
studied 990 551 305 100 1000 plants
Early maturing
lines (%) 0.2 3.6 4.0 10.0 0
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