18. Spontaneous "57 H" mutants in rice
    Hikani Satoh 1 , Toshihiro Kumamaru2, Masahiro Ogawa3 ,Mikio Siraishi4 , Byeong Gi Im5 ,
    Min Yon Son1 and Yoko Takemoto3

    1) Institute of Genetic Resources, Faculty of Agriculture, Kyushu University, Hakozaki, Fukuoka,
                        812 Japan.
    2) Plant Breeding and Genetics Research Laboratory, Japan Tabacco Inc., lwata, Shizuoka, 438 Japan.
    3) Yamaguchi Women's University, Sakurabatake, Yamaguchi, 753 Japan.
    4) Oh-lta Agricultural Experimental Station, Usa, Oh-lta, 872-01 Japan.
    5) Seoul Women's University, Seoul, 139-744 Korea.

    Some of mutants for the 57H character, which have a high accumulation of 57 kD polypeptides of rice storage proteins, were induced by an MNU treatment of rice (Kumamaru et al. 1988). So far three loci, esp-2, Glup-l (Gup-1) and glup-2 (gup-2), have been identified for the 57H mutation in rice, and have been located on chromosome 11, 9 and 9, respectively (Kumamaru et al. 1987; Satoh et al. 1994). We found that 57H mutants occurred spontaneously in rice accessions which were introduced from North Asian countries in 1930s and preserved in Kyushu University. The spontaneous 57H mutants were characterized by the remarkably increased content of 57 kDa polypeptide with the markedly decreased content of 40 kDa (glutelin acidic subunit) and 20 kDa (glutelin basic subunits) polypeptides in the SDS-PAGE. Nineteen 57 H mutant strains were so far observed in 1400 accessions, from Russia, Northern China and North Korea. The phenotype of these spontaneous 57 H mutants were very similar to each other.
    Seven 57H mutant were reciprocally crossed with normal cultivars, Kinmaze and T65. The phenotype of F1s was normal and the segregation of normal and mutant types in F2s showed a good fit to a 3:1 ratio. These results indicated that the spontaneous 57H mutants are due to single recessive genes. Nineteen mutants were crossed with each other, The phenotypes of F1S were 57H type in all of the cross combinations, and no segregation of normal type in the F2 s was found and all of the F2 seeds derived from these cross combinations showed the mutant phenotype. These results show that the spontaneous 57H mutants were due to allelic genes.
    Some of the spontaneous mutant strains were crossed reciprocally with three marker lines, CM1787 for esp-2, EM61 for Glup-l and EM305 for glup-2. Table 1 shows the phenotype of F1 seeds and the segregation patterns in F2 seeds derived from crosses of a spontaneous 57H mutant strain, H01055, with CM1787, EM61 and EM305. The F1 seeds from the cross between H01055 and CM1787 showed the normal phenotype, and F2 seeds were classified into normal, CM1787 and H01055 type. Since the double mutant phenotype was not able to distinguish from the CM1787 type except for a few cases, segregation of these three types fitted the expected ratio of 9:4:3. These results suggested that 57-H mutant gene of H01055 is not allelic to esp-2 of CM1787, and that esp-2 and the 57-H mutant gene of H01055 show the additive effect on the accumulation of 57 kD polypeptides.
    F1 seeds from the cross between EM61 and H01055 showed the mutant phenotype of EM61, and F2 seeds were classified into normal, EM61 and H01055. Since the double

Table 1. Segregation pattern of 57-H character in F1 seeds of crosses between a
        spontaneous 57H mutant, H01055, and three marker lines for 57-H gene,
        CM 1787, EM61 and EM305
 

Cross combination F1 seed Segregation in F2 X2
Normal H01055 CM1787 Total (9:4:3)
H01055 X CM1787 Normal
112 45 37 194 0.35
Normal H01055 EM61 Total (3:4:9)
HO 1055 X EM61 57-H
46 53 100 199 3.51
Normal H01055 EM305 Total (9:4:3)
HOI 055 X EM305 Normal
89 42 27 158 x^2

mutant phenotype was not able to distinguish from the H01055 type, segregation of these types fitted the expected ratio of 3:4:9. These resullts suggested that 57-H mutant gene of H01055 is not allelic to Glup-l of EM61. The F1 seeds of the cross between H01055 and EM305, were normal for the 57-H character, and the F2 seeds were classified into normal, EM305 and H01055 types. As the doubly recessive type could not be identified from the 57-H mutant type of H01055 though some of them showed the double mutant phenotype, the segregation fitted the expected 9:3:4 ratio, indicating that the 57-H mutant locus of H01055 is different from glup-2. The same results were obtained in the cross combinations between the other spontaneous 57H mutant strains and the three marker lines.
    Furthermore, trisomic analysis of a spontaneous 57-H mutant, H01055, revealed that segregation of F2 seeds between the mutant and trisomic E plant fitted to the trisomic segregation ratio (Table 2). The new mutant gene of H01055 is designated as glup-3(t) (glutelin precursor mutant-3(t)) and that the gene is located on chromosome 4.
 

Table2. Segregation of normaland 57-H in F2 seeds set onTriplo
F1 plants derived from the crosses between 
and a spontaneous 57H mutant, H01055
Type of Trisomics  Segregation in F2 X2 (1:3)
Normal 57-H Total
Triplo 4  177 23 200 19.44**
Triplo 5  31 9 40 0.13
Triplo 6  151 49 200 0.03
Triplo 7  31 5 36 2.37
Triplo 8  29 8 37 0.23
Triplo 9 29 10 39 0.01
Triplo 10  31 8 39 0.42
Triplo 11  88 32 120 0.18
Triplo 12  30 9 39 0.08

References

Kumamaru, T., H. Satoh, N. Iwata, T. Omura and M. Ogawa, 1987. Mutant for rice storage proteins.
    III. Genetic analysis of mutants for storage proteins of protein bodies in the starchy endosperm.
    Jpn. J. Genet. 62: 333-339.
Kumamaru, T., H. Satoh, N. Iwata, T. Omura, M. Ogawa and K. Tanaka, 1988. Mutants
    for rice storage proteins. I. Screening of mutants for storage proteins of protein bodies in the
    starchy endosperm. Theor. Appl. Genet. 76:11-16.
Satoh, H., T. Kumamaru, S. Yoshimura and M. Ogawa, 1994. New 57 kDa glutelin genes on
    chromosome 9 in rice. Rice Genet. Newsl. 11: 158-161.