Coll. of Agric. & Life Sci., Seoul Nat'l Univ., Suwon, 441-744 Korea
Fifty dwarfing genes have been reported in rice (Kinoshita and Takahashi 1991). Among them, D-53 was the only dominant gene (Iwata et al. 1977). We identified another dominant dwarfing gene induced by N-methyl-N-nitrosourea from a Korean Japonica cultivar, Hwachung.
Some agronomic characteristics of the dwarf Hwachung line and its F\1\ plants
Table 1. Heading date, panicle and internode lengths of dwarf-Hwachung line, original cultivar, Hwachung, and their F\1\ ============================================================================== Heading Panicle Length of internode (cm) date length (cm) 1 2 3 4 5 Total Hwachung (A) Aug. 23 18.9 34.7 21.4 17.1 13.5 5.6 92.3 Dwarf-Hwa. line (B) Aug. 20 14.0 26.7 16.4 12.0 8.0 3.8 66.9 F\1\ (C) Aug. 21 14.8 29.5 17.7 13.2 9.7 3.2 73.3 Difference (A vs B & C) * ** ** ** ** ** * ** (B vs C) ns ns ns ns ns ns ns ns Ratio of B/A (%) - 74.1 76.9 76.6 70.2 59.3 67.9 72.5 ==============================================================================
Table2. Grain dimension of dwarf-Hwachung line, original cultivar, Hwachung, and their F\1\ ============================================================================== Grain dimension of brown rice ============================= 1000-a) Length Width Thick. L/W grains wt. ============================================================================== -(mm)- (g) Hwachung (A) 0.502 0.292 0.210 1.72 24.8 Dwarf-Hwa. line (B) 0.396 0.273 0.188 1.45 17.4 F\1\ (C) 0.399 0.272 0.193 1.47 18.9 Difference (A vs B & C) ** ** ** ** ** (B vs C) ns ns ns ns ns ============================================================================== a) rough rice
Fig. 1. Distribution of culm length in F\2\ populations between Hwachung and its dwarf line, and between a dwarf (D-h) and a tall (T-h) plant derived from a segregating population. The short:tall ratios fitted 3:1 with high probabilities.
Fig. 2. Distribution of culm length in F\2\ populations from crosses of FL282 (D-53) with Hwachung (H) and its dwarf line (D-h).
For comparison, line FL282 carrying gene D-53 was crossed with Hwachung and its dwarf line. As shown in Fig. 2, the F\2\ ratio for short and tall plants was 3:1 in the cross FL282 x Hwachung. In FL282 X dwarf-Hwachung and its reciprocal cross, however, the F\2\ plants showed continuous variations and a few of them had the normal height of Hwachung (these may be assumed to be 1/16 of total plants). This suggests that genes D-53 and D-h are non-allelic and independent of each other.
The dwarf Hwachung line has a good plant type with short-compact panicles and small-round grain. Culm and panicle lengths showed high correlations in F\2\ populations, suggesting pleiotropic effects of gene D-h on both characters (Table 3).
We thank Dr. Nobuo Iwata for providing line FL282 with D-53.
Table 3. Correlation coefficients between culm and panicle length in F\2\'s of dwarf-Hwachung cross (all significant at 1% level) ============================================== Cross combination r\ph\ r\g\ DF ============================================== Hwachung/Dwarf-Hwa. 0.72 0.80 523 Tall-Hwa./ " 0.80 0.95 501 Dwarf-Hwa./Tall-Hwa. 0.73 0.86 517 ============================================== r\ph\ and r\g\: phenotypic and genotypic correlation coefficient
Iwata, N., H. Satoh and T. Omura. 1977. Linkage studies in rice. Linkage groups for 6 genes newly described. Japan J. Breed. 27 Suppl. 1: 250-251.
Kinoshita, T. and M. Takahashi. 1991. The 100th report of genetical studies on rice plant-linkage studies and future prospects. J. Fac. Agr. Hokkaido Univ. 65(1): 1-61.