32. Isozyme variations and ecotype-specific Pgd- 1 alleles found among Japanese rice varieties

Ryuji ISHIKAWA

Faculty of Agriculture, Hirosaki University, Hirosaki, 036 Japan

A total of 450 lowland and 66 upland Japanese varieties were examined for isozymes at 17 loci. Those varieties were classified into the Indica and Japonica types by diagnostic isozyme genes (Ishikawa 1990). Thus, 99% of lowland and 977o of upland varieties were classified as Japonicas, but a few remainders were classified as Indicas. Most of the lowland Japonicas showed genotype-type 1 and most of upland Japonicas type 2 (Table 1). The Indica-like varieties, though very few, had various genotypes. The genotypes of lowland Indicas varied from type 3 to type 7, and those of upland Indicas showed zymogram-type 8 or 9.

Of the 17 loci examined, alleles at locus Pgd-1 (phosphogluconate dehydro- genase) were found to characterize the lowland and upland Japonica and the Indica types (Table 2). The Indica-like varieties showed some morphological characteristics of the Indica type, e.g., relatively short apiculus hairs (0.23 to 0.55 mm, mean for Japanese Japonicas being 0.87 mm), relatively large length-width ratio of spikelets (2.62 to 3.07, mean for Japanese native Japonicas being 1.96), and positive phenol reaction in most of them. They also showed red color of pericarp, although a few other native varieties also showed red pericarp. Although the history of introduction of lowland rice into Japan is not known well, most of the upland varieties were introduced from China relatively recently. Probably, the Indica-like varieties belong to the so-called "red rice" which was introduced several hundred years ago.

 

            
Table 1. Alleles at 17 isozyme loci found in Japanese varieties.
         Lowland.Japonica-Type 1; Upland Japonica-Type 2;
         Lowland Indica-Types 3 to 7; Upland Indica-Types 8 & 9.
==============================================================================
                                      Isozyme  genotype
                    [Japonica] [            Indica-like              ]
                    __________________________________________________
Locus                1    2       3    4    5    6    7    8    9
==============================================================================
Acp-1                2    2       1    2    1    1    1    1    1
Adh-1                1    1       1    1    1    1    1    1    1
Amp-1                1    1       1    1    1    1    1    1    1
Amp-2                1    1       2    2    2    2    2    2    2
Amp-3                1    1       1    1    1    3    1    3    1
Cat-1                2    2       1    1    1    1    1    2    1
Est-2                0    0       2    0    0    0    2    0    2
Est-5                1    1       1    1    1    1    1    1    1
Est-9                1    1       2    1    2    1    2    1    1
Mal-1                1    1       2    2    2    1    2    2    2
Pgd-1                1    2       3    3    3    3    3    3    3
Pgd-2                1    1       1    1    1    1    1    1    1
Pgi-1                2    2       1    1    0    1    1    1    1
Pgi-2                1    1       2    2    2    2    2    2    2
Pgi-3                0    0       0    1    1    1    1    1    1
Pox-2                0    0       1    0    1    0    1    0    0
Sdh-1                2    2       2    2    2    2    2    2    2
===============================================================================

Table 2. Frequencies of three Pgd-1 alleles found among Japanese lowland and
upland varieties
===============================================================================
                                              No. of varieties
Ecotype        Varietal group    ==============================================
                                  Pgd-11            Pgd-12          Pgd-13  
===============================================================================
Lowland          Japonica            445                 0               0
                 Indica                0                 0               5
Upland           Japonica             11                53               0
                 Indica                0                 0               2
===============================================================================

Reference

Ishikawa, R., 1990. Analysis of two isozyme genes, Mal-1 and Pgi-3 and their frequencies in Indica and Japonica types. RGN 7: 100-102.