7. American long-grain rice varieties belong to subspecies japonica

Y. I. SATO1 and I. NAKAMAURA2

1) National Institute of Genetics, Mishima, 411 Japan
2) Iwate Biotechnology Research Center, Kitakami, 024 Japan

Rice varieties grown in USA are traditionally classified into long, medium, and short grain-types. The long-grain varieties have been considered as indica, while the short and medium grained ones are japonica. The authors collected 169 long-grain varieties from experimental stations in Louisiana, Texas, Arkansas and other southern states, and examined them with regard to phenol reaction, potassium chlorate (KC1O3) tolerance (1.5% solution, immersed for 4 days), and isozyme alleles at seven loci (Table 1). Most of the varieties (163/169) showed negative phenol reaction and high tolerance to potssium chlorate, and their zymograms were those characterizing japonica. Furthermore, 21 of them were examined with regard to the presence or absence of a deletion at the ORF 100 region of Pst-12 fragment in chloroplast DNA (cf. Kanno et al. 1993). This deletion is frequent in indicas but seldom in japonicas (Chen et al. in press). All the cultivars examined were non-deletion types which characterize japonicas. Thus, it may be concluded that most of the American long-grain cultivars are japonicas.


Table 1.  Alleles at seven isozyme loci detected in 169 American long-grain
cultivars
===============================================================================
Code                Alleles observed at                No. of alleles    No. of
      Amp-3  Acp-1  Cat-1  Est-2  Pgi-1  Pgi-2  Pox-2 differing from A cultivars
===============================================================================
A      1      2      2      0      2      1      0    Typical japonica      84
B      1      2      1      0      2      1      0    jaoponica-like
C      1      2      2      1      2      1      0            "       1     79
D      1      2      1      1      2      1      0            2              1
E      1      2      1      1      2      1      1            3              1
F      2      1      1      0      2      2      1            5              2
G      2      1      1      1      2      2      1     indica-like    6      2
Total                                                                      169
===============================================================================

References

Chen, W.B., Y.I. Sato, I. Nakamura and H. Nakai, 1993. Indica--japonica differentiation in traditional Chinese rice cultivars. Euphytica (in press).

Kanno, A., N. Watanabe, I. Nakamura and A. Hirai, 1993. Variations in chloroplast DNA from rice (Oryza sativa): differences between deletions mediated by short direct-repeat sequences within a single species. Theor. Appl. Genet. 86: 579-584.