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Laboratory of Plant Breeding, Faculty of Agriculture, Hirosaki University, Hirosaki, 036 Japan
Two genes encoding isozymes of MDH (E.C.1.1.1.40) and PGI (E.C.5.3.1.9) were analysed by using polyacrylamide and starch gel electrophoresis, respectively. Their segregation patterns were observed in an F2 population from Shiokari X C8005 (Table 1; Fig. 1). The enzyme encoded by Mal-1 is NADP-dependent malate dehydrogenase with dimeric structure. The codominant genes seem to be identical to those detected on starch gel and reported as Mal-1 (malic enzyme-1) by Glaszmann et al. (1988). Gene Pgi-3 exhibits a single band which is faster than the bands expressed by Pgi-1 and Pgi-2. Most probably, it corresponds to the Pgi-3 gene reported by Glaszmann et al. (1984).
Pgi-3, Mal-1, and seven other isozyme genes were studied as to their allele frequencies in 60 varieties from different Asian countries, which had been classified into Indica and Japonica types by diagnostic characters (a part of variation testers, Oka 1958). Allele 1 was predominant at the Mal-1 locus in the Japonica and allele 2 in the Indica groups. At the Pgi-3 locus, also, allele G (null) was predomiant in Japonica and 1 in Indica type. Thus, the two newly observed genes both showed differential frequencies between the two types. Allelic frequencies at other seven loci were obtained earlier (Table 2).
The D scores showing differential frequencies of isozyme alleles between the Indica and Japonica types were computed for respective alleles, which were proposed by Morishima and Gadrinab (1987) as D\Ind\ = F\Ind\/(F\Ind\ +F\Jap\). When a variety is tested for these isozyme loci, its mean D\Ind\ value (D-\Ind\) shows its likeness to the Indica type. The distribution Of D\Ind\ values based on the 9 loci among the 60 tester-varieties indicated that the Indica and Japonica types were classifiable clearly by the frequencies of these isozyme alleles (Fig. 2).
Table 1. Segregation patterns for Mal-3 and Pgi-3 observed in the F2 of Shiokari X C8005
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Parental genotype No. of F2 plants
Locus ================= ================== X2 from 1:2:1
Shiokari C8005 A/A A/B B/B or 3:1
(A/A) (B/B)
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Mal-1 1/1 2/2 18 37 14 0.83(P>0.5)
Pgi-3 0/0 1/1 45 158 0.73(P>0.3)
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Shiokari- A Japonica variety from Hokkdido, Japan
C8005- An Indica variety from CRRI, Cuttack, India
Table 2. Nine isozyme loci showing differential allelic frequencies between Indica and Japonica types each represented by 30 varieties
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No. of varieties
Locus Chromosome Allele ================= D/Ind score
Indica Japonica
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Acp-1 12 +9 0 30 0.0
-4 30 0 1.0
Amp-2 8 1 2 28 0.07
2 28 2 0.93
Cat-1 6 1 29 1 0.97
2 1 29 0.03
Est-2 6 0 9 24 0.27
1 9 5 0.64
2 12 1 0.93
Mal-1 1a 1 0 25 0.0
2 30 5 0.85
Pgi-1 3 1 26 0 1.0
2 4 30 0.12
Pgi-2 6 1 10 29 0.25
2 20 1 0.96
pgi-3 (unknown) 0 2 26 0.07
1 28 4 0.88
Pox-2 12 0 8 29 0.22
4C 22 1 0.96
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a-Personal communication to Dr. H. Morishima from Dr. J. C. Glaszmann (1990)
Fig. 2. Distribution of D\Ind\ values based on 9 isozyme loci given in Table
2. Dotted bars- Indica; open bars-Japonica, as classified by Oka (1958).
References
Glaszmann, J. C., H. Benoit and M. Arnaud, 1984. Classification de riz cultives (Oryza sativ. L.). Utilization de la variabilite isoenzymatique. Agr. Trop. 39: 51-66.
Glaszmann, J. C., B. G. de los Reyes and G. S. Khush, 1988. Electrophoretic variation of isozymes in plumules of rice (Oryza sativa L.). A key to the identification of 76 alleles at 24 loci. IRRI Res. Paper Series 134, p. 1-14.
Morishima, H. and L.U. Gadrinab, 1987. Are the Asian common wild rices differentiated into the Indica and Japonica types? In S.C. Hsieh (ed.), Crop exploration and Utilization of Genetic Resources, p. 11-20. Taichung Distr. Agric. Improvement Station, Changhua, Taiwan.
Oka, H. I., 1958. Intervarietal variation and classification of cultivated rice. Ind. J. Genet. Plant Breed. 18: 79-89.
