H. Hasegawa 1, S. Mori 2, M. Inoue 1 and M. Murakami 2
1) Radiation Center of Osaka Prefecture, Shinke-cho, Sakai, Osaka, 593 Japan; and 2) Faculty of Agriculture, Kyoto Prefectural University, Shimogamo, Sakyo- ku, Kyoto, 606 Japan
We have obtained 24 mutants resistant to hydroxy-L-proline (Hyp), a proline analog, from the M2 populations of a rice cultivar, Nipponbare, mutagenized with ethylene imine, ethyl methanesulfonate and sodium azide (Hasegawa and Inoue 1983). Three M4 lines, HYP 101, HYP 202 and HYP 203 (all induced by 0.2% ethylene imine) were established as homozygous lines.
The difference in Hyp resistance between the mutants and the original variety was confirmed when the seeds were cultured with 10-3 M Hyp for 10 days. The three mutant lines were crossed with the original variety reciprocally. The F2 data showed that in each mutant the Hyp resistance was controlled by a single recessive gene. The genes in HYP 101, HYP 202 and HYP 203 are tentatively symbolized as hpr-1, hpr-2(t) and hpr-3(t), respectively, although the allelic relationships between the three genes are not known.The mutant lines also showed some differences in culm length and other traits as compared to those of the original variety (Table 1).
Table 1. Characters of Hyp resistant mutants
============================================================================== Traits Nipponbare HYP 101 HYP 202 HYP 203 (+) (hpr-1) (hpr-2(t)) (hpr-3(t)) ============================================================================== Culm length (cm) 72.4 67.0** 67.6** 70.0 Panicle length (cm) 22.9 19.6** 20.5** 20.0** 100 seed weight (g) 2.57 2.35** 2.39** 2.35** Days to heading 93.7 91.0** 92.2** 93.2* ==============================================================================
*,** Significantly different from Nipponbare at 5% and 1% levels, respectively.
The mutant lines did not accumulate free proline in the seeds or in the seedlings. These may be useful in the study of proline metabolism. The resistance genes may serve as gene markers since they can be easily scored at the young seedling stage.
Hasegawa, H. and M. Inoue, 1983. Induction and selection of hydroxy-L-proline resistant mutants in rice. Jpn. J. Breed. 33: 275-282.