6. An altitudinal cline of isozyme variation found in land-race populations of Nepalese rice

Reiko Sano1, Takeo Konishi2 and Hiroko Morishima 1

1)National Institute of Genetics, Mishima, 411 Japan

2)Institute for Agricultural and Biological Sciences, Okayama University, Kurashiki, 710 Japan

The Indica and Japonica rice cultivars can be distinguished by multivariate analysis of isozyme variations as reported by Second (1982) and Glaszmann et al. (1984). Frequency distribution of multilocus genotypes for six diagnostic isozyme loci found in the Indica and Japonica varietal groups, classified on the basis of character-association pattern, is given in the bottom lines of Table 1.

To see how genetic variation among rice cultivars is related to changing altitude, 16 populations of land races collected at different altitudes in Nepal were assayed for the above six isozymes by starch-gel system. The loci examined were Cat-1, Pgi-1, Pgi-2, Acp-1, Pox-2 and Est-2. The variation pattern observed in these materials showed a cline corresponding to the altitude of collection sites (Table 1). The samples collected at the sites higher than 1750 m, consistently showed a particular genotype which was specific to the Japonica type. Those collected at the lower altitudes were heterogeneous among and within populations and exhibited various genotypes which were found in the Indica type. The distribution pattern of rice cultivars in the hilly areas might be conditioned by dissemination and isolation under diverse natural and ethnological conditions. yet, the present result suggests that, in Nepal, the Indica and Japonica types are distributed in the low and high altitudes, respectively.

Table 1. Between-and within-populational variations in isozyme genotypes found in Nepalese land-races collected at different altitudes.

==============================================================================
                 Locus           Isozyme genotype
                          ----------------------------------------
                 Cat-1    2  2  2  2  2  1  1  1  1  1  1  1  1  1  1  1  1  1
                 Acp-1   +9 +9 -4 -4 -4 +9 +9 +9 +9 -4 -4 -4 -4 -4 -4 -4 -4 -4
                 Pgi-1    2  2  2  2  1  2  2  2  1  2  2  2  2  2  1  1  1  1
                 Pox-2    0  0  0  0 4C  0  0 4C  0  0  0  0 4C 4C  0  0 4C 4C
                 Pgi-2    1  4  1  4  1  1  2  2  1  1  2  4  1  2  1  2  1  2
                 Est-2   {0  1 {0  1  0 {0  2  2  1  1 {1  0  2  1 {0 {0 {0 {0
                          1     1        1              2           2  1  1  1
                                                                       2  2  2
Nepalese land races
Popu-   No.of   Alt.
lation  plants  (m)
--------------------      ----------------------------------------------------
KK-3      13    1970     11  2
JENA46-48  3    1780      3
JENA51-52  2    1770      2
KT-8       6    1770      6
JENA54-55  2    1750      2
KT-7A     14    1750            8  6
KT-7B     21    1750            8  11        1           1
PK-2       4    1500                      1                 3
KK-1      32    1500                                     2         30
JENA39-42* 4    1460                      3  1
JENA30-38* 8    1460                      1  7
JENA24-28* 4    1457                         4
JENA20-23  4    1440      2                              1                1
JENA15-17  3    1440      1                           1             1
KK-4A      6     760                                                1  4     1
JENA60     1     350                                                   1
-----------------------------------------------------------------------------
Asian varieties
Japonica type            50
Indica type                           1          1  1     6    1 2  4  3  9 20
==============================================================================
For Est-2, different alleles are pooled to save space.

*Upland field.

References

Glaszmann, J.C., H. Benoit and M. Arnaud, 1984. Classification de riz cultivars (Oryza sativa L.): Utilisation de la variabilite isozymatique. Agr. Trop. 39:51-66.

Second, G., 1982. Origin of the genic diversity of cultivated rice (Oryza spp.): Study of the plymorphism scored at 40 isozyme loci. Jpn. J. Genet. 57:25-57.