Classification of Japanese rice varieties into Indica and Japonica types by using isozyme genotypes.

Abstract

Sixty Asian varieties (Oryza sativa L.) which had been classified into Indica and Japonica types based on diagnostic characters (OKA 1958), were investigated for the genotypes of 10 isozyme species including 17 Ioci (Fig. 1 and 2, Table 1, 2 and 4). Genotypic frequencies at 11 loci, Acp-1. Amp-2. Cat-1. Est-2, Mal-1, Pgd-1. Pgi-1. Pboi-2, Pgi-3. Pox-2 and Sdh-1 were significantly different between Indica and Japonica types (Table 5). Discriminant scores (D scores) for Indica and Japonica varieties were calculated for the above eleven loci. However, the alleles at Pgd-1 and Sdh-1 Ioci were not enough to discriminate between Indica and Japonica types. D score averaged over the nine loci excluding Pgd-1 and Sdh-1, appeared to be more useful than that based on the eleven loci (Table 7). Thus, the Asian varieties were classified by using D scores averaged over the nine loci (Fig. 3A). Japonica varieties except for one and Indica varieties classified by OKA (1958) showed D scores ranging from 0.12 to 0.30 and from 0.69 to 0.94, respectively. Only one Japonica variety showed D scores with a value of 0.6. Because the variety carried alleles frequently found in Japonica type varieties, only at Acp-1, Mal-1 and Pgi-1 and alleles frequently found in Indica type varieties at other six loci, it appeared to be a 'recombinant type' between Indica and Japonica varieties. Based on these results, varieties with D scores ranging from 0.0 to 0.4 and from 0.6 to 1.0 were confirmed to be Japonica and Indica types, respectively, and newly used Pgi-3 and Mal-1 were also confirmed to be useful for discriminating the varieties.