12. A new dominant dwarfing gene in rice

Hee-Jong KOH and Mun-Hue HEU

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


with Hwachung are shown in Tables 1 and 2. All internodes and panicle were reduced in length to about 70% of values of the original cultivar, and the grain were smaller and rounder. The F\2\ plants had the same phenotype as the dwarf line, showing that the dwarfness was dominant over the tall stature. Segregation patterns of culm length in F2 populations between Hwachung and its dwarf line, and between a tall and a dwarf plant derived from their heterozygous population are shown in Fig. 1. Short and tall plants segregated in a 3:1 ratio. This indicates that the dwarfness is controlled by a single dominant gene, which we have designated D-h.



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

References

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.