25. Linkage analysis of genes, ge (giant embryo) and esp-l (endosperm storage protein-1) on chromosome 7

        Toshihiro Kumamaru and Hikaru Satoh

1) Plant Breeding and Genetic Research Laboratory, Japan Tobacco Inc., Higashibara, Toyoda. Iwata,
    Shizuoka 438, Japan.
2) Faculty of Agriculture, Kyushu University, Hakozaki, Fukuoka 812, Japan     Various kinds of mutants for endosperm traits have been obtained by the treatment of fertilized egg cells with N-methyl-N-nitrosourea (Satoh and Omura 1981; Satoh 1985). These mutants are useful for the improvement of rice grain quality and also for linkage mapping. The trisomic analysis for two mutant, ge for a giant embryo (Satoh and Omura 1981) and esp-l (endosperm storage protein mutant-1) characterizing the low content of 13b polypeptide (prolamin)(Kumamaru et al. 1988), indicated that the two genes are located on chromosome 7 (Kumamaru et al. 1987; Satoh and lwata 1990) and ge linked with v-ll and rfs, with the recombination values of 38.9 ±4.1% and 20.9 ± 2.9%, respectively (Satoh and lwata 1990). The detailed map of chromosome 7 showing positions of these genes has not been prepared.
    CM21 (esp-l) was crossed with EM40 (ge) and some of marker lines with d-6, g, spl-5, v-ll and rfs, which are located on chromosome 7. The F2 and F3 data show that esp-l is linked tightly with ge and rfs with the recombination values of 4.7 ± 1.5% and 20.6 ± 3.4%, respectively, and no linkage was detected between esp-l, d-6, g, spl-5 and v-11 (Table 1 and 2). From these results, the order of the genes on chromosome 7 was estimated to be d-6— g—spl-5— v-ll—rfs-esp-l-ge as shown in Fig. 1.
 
Table 1. Linkage analysis between esp-l and marker genes on chromosome 7
Gene pair Phase Segregation in F2 X2
AB Ab aB ab Total (9:3:3:1)
esp-l X d-6 Repulsion 178 52 47 17 294 0.44
esp-I X g Repulsion 186 49 50 13 298 0.01
esp-I X spl-5 Repulsion 179 58 57 11 305 1.64
esp-l X v-ll Repulsion 108 30 26 3 167 0.73
esp-I Xspl-5 Repulsion 84 51 37 4 176 13.1**
**: Significant at 1% level. Table 2. Segregation patterns in F3 derived from crosses between
    esp-l and two marker genes, ge and rfs
 
+ esp-l
++ +ge ge ge ++ +ge ge ge R.V.
8 99 50 42 1 0 4.7% ± 1.5
+ esp-l
++ +rfs rfs rfs ++ +rfs rfs rfs R.V.
21 77 38 25 12 0 20.6%±3.4
  References

Kumamani, T., H. Satoh, N. Iwata, T. Omura and M. Ogawa, 1987. Mutants for rice storage proteins. III.
    Genetic analysis of mutants for storage proteins of protein bodies in the starchy endosperm. Japan. J. Breed.
    62:333-339.
Kumamani, T., H. Satoh, N. Iwata, T. Omura, M. Ogawa and K. Tanaka, 1987. Mutants for rice storage
    proteins. 1. Screening of mutants for storage proteins of protein bodies in the starchy endosperm.
    Theor. Appl. Genet., 76:11-16.
Satoh, H. and T. Omura, 1979. New endosperm mutations induced by chemical mutagens in rice, Oryza sativa
    L. Japan. J. Breed. 31: 316-326.
Satoh, H. and N. Iwata, 1990. Linkage analysis in rice. On three mutant loci for endosperm properties,
    ge (giant embryo), du-4 (dull endosperm-4) and flo-I (floury endospcrm-l). Japan J. Breed. 47
    (Suppl. 2): 268-269. (in Japanese)