27. Linkage analysis for four isozyme loci, Adh-1, Acp-1, Pox-2 and Pgd-2

R. ISHIKAWA1 and H. MORISHIMA2

1) Faculty of Agriculture, Hirosaki University, Hirosaki, 036 Japan

2) National Institute of Genetics, Mishima, 411 Japan

Two isozyme loci Pdg-1 and Adh-1 were found to belong to linkage group VIII by trisomic analysis (Ranjhan et al. 1988; Ishikawa et al. 1989). First, for mapping these loci, a Japonica linkage tester FL280 carrying Adh-12, Pgd-12, la (lazy habit) and v-4 (virescent-4) was crossed with an Indica strain Ac437 carrying Adh-13 and Pgd-11. In the F2, Adh-1 was found to be linked with v-4 (Table 1a), but not with la. The recombination value between Adh-1 and v-4 was 26.8+/-5.3%. As reported earlier (Ishikawa et al. 1988), Pgd-1 is linked with both la (14.2+/-4.9%) and v-4 (5.4+/-3.0%). Accordingly, the locations of these four loci are as as shown in Fig. 1.

Second, Acp-1 and Pox-2 belonging to the linkage group of d-33 were reexamined. A Japanica tester FL27 carrying d-33, Acp-19 and Pox-20 was crossed with an Indica strain Ac435 carrying Acp-14 and Pox-24C In the F2, d-33 showed linkage with both Acp-1 (29.2%+/-3.9%) and Pox-2(7.6+/- 0.1%; Table 1 b). In this cross, the recombination value between Acp-1 and Pox-2 was found to be 23.9+/-3.6%, which was lower than the values (27-34%) reported by Pai et al. (1975) in two crosses between cultivated and wild rice strains and also the value (28%) found in a cross between two Indica varieties by Wu et al. (1988). The differences between these estimates are probably due to segreation distortion frequently found in Indica-Japonica crosses. The gene order of the three loci may be: d-33-Pox-2

Table 1. Linkage relations and recombination values (p) obtained
         in two crosses
  a) FL280 (Adh-12;v-4) X Ac437 (Adh-13; + v-4)
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v-4              Adh-1                 Total         p(%)
          3/3     3/2        2/2
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Normal     27     33          6          66
                                                  26.8+/-5.27
Virescent   3     11         12          26
  Total    30     44         18          92
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b)FL27(d-33;Acp-19;Pox-20)xAc435(+d-33;Acp-1-4;Pox-24c)
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Gene linked           Acp-1           Total          p(%)
            -4/-4     -4/+9   +9/+9
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Pox-2  4C      46      78        19    143
                                                 23.9+/-3.58
        0       3      12        21     36
d-33  Normal   47      74        24    145
                                                 29.2+/-3.93
      Dwarf     2      16        16     34
     Total     49      90        40    179
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d-33                  Pox-2          Total           p(%)
                  4C         0
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     Normal      138         7         145
                                                  7.6+/-2.07
     Dwarf         5        29          34
       Total     143        36         179
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Fig. 1. Mapping of four genes belonging to linkage group VIII.

-Acp-1.

Third, a line derived from T65 X W120 carrying Pgd-23, Est-23 and Pgi-21 was crossed with IR36 which had Pgd-21, Est-22 and Pgi-22. The F2 population showed that these three loci are linked and all belong to linkage group I. Their recombination values were estimated (Table 2). Pgd-2 seemed to be located between wx and Est-2 (Fig. 2).

Table 2. Linkage relations and recombination values (p) obtained in the cross between an F4 line derived from Taichung 65 X W120 (wild) carrying Pgd-23, Pgi-21 and Est-23 and IR36 carrying Pgd-21, Pgi-22 and Est-22

a) Pgi-2 with Pgd-2 and Est-2
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                        Pgi-2
Gene linked     2/2      2/1       1/1     Total      p (%)
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Pgd-2   1/1       3        7         2        12
        1/3       4       15         1        20    30.8+/-6.62
        3/3       0        8         7        15
Est-2   2/2       6        4         0        10
        2/3       1       22         2        25    12.7+/-3.43
        3/3       0        4         8        12
  Total           7       30        10        47
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b)Between Pgd-2 and Est-2
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                       Pgd-2
Gene linked     1/1     1/3       3/3       Total     p(%)
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Est-2    2/2      4       5         1          10
         2/3      7      14         4          25   25.5+/-5.40
         3/3      1       1        10          12
  Total          12      20        15          47
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Fig. 2. Mapping of five genes belonging to linkage group 1. The recombination value between wx and Est-2 (31%) is based on Current linkage map (RGN 4:11).

References

Ishikawa, R., T. Kinoshita and H. Morishima, 1988. Linkage analysis of the Pgd-1 locus. RGN 5: 81-82.

____, H.Morishima, K. Mori and T. Kinoshita, 1989. Chromosomal analysis of isozyme loci and the allelic expression at cellular level in rice. Genetical studies on rice plant, 97.J. Fac. Agr. Hokkaido Univ. 64: 85-98.

Pai, C., T. Endo and H,.I. Oka, 1975. Genic analysis for acid phosphatase isozymes in Oryza perennis and O. sativa. Can. J. Genet. Cytol. 17: 637-650.

Ranjhan, S., J. C. Glaszmann, D. A. Ramirez and G. S. Khush, 1988. Chromosomal localization of four isozyme loci by trisomic analysis in rice (0ryza sativa L.). Theor. Appl. Genet. 75: 541-545.

Wu, K. S., J. C. Glaszmann and G. S. Khush, 1988. Chromosomal locations of ten isozyme loci in rice (Oryza sativa L.) through trisomic analysis. Biochem. Genet. 26: 303-320.