To investigate alcohol dehydrogenase (Adh, E.C. 1.1.1.1) isozyme variability in Oryza sativa complex for environmental stress tolerance, Adh1 locus was assayed by starch-gel (system H, Tris-citric pH 7.6) methods (Glaszmann et al. 1988). A total of 92 rice strains consisting of Oryza sativa, Oryza rufipogon, and Oryza barthii from worldwide distribution were studied. Enzyme extracts were prepared from 1-5 shoots, 2-4 days after germination at 32^oC in incubator. The stained bands were read using the systems suggested by Morishima and Glaszmann et al. (1990).

Table 1 summarizes distribution of four alleles of Adh1 in Oryza sativa complex. Polymorphism for three alleles (Adh1-1, Adh1-2, and Adh1-3) was not observed within the groups of lowland rice and Oryza rufipogon, it suggested that there is no indica-japonica differentiation at Adh1 locus in lowland rice as well as in Oryza rufipogon. By contrast,

polymorphism for two alleles (Adh1-1 and Adh1-2) was observed in upland rice. It implied that upland rice is more adaptable to diverse environments, and may play important role in indica-japonica differentiation. Among the strains investigated, only one Pakistan rice variety, Basmati 385, possessed the Adh1-3 allele, and only the Chinese weedy rice strain Lu-tao possessed the null allele, Adh1-0 (Fig. 1).

Adh is believed to associated with environmental stress such as cold and drought tolerance, thus, some desirable traits of upland rice are probably associated with isozyme markers of Adh1-2. This study provided information for environmental stress tolerance research.

References

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: 14.

Morishima, H. and J.C. Glaszmann, 1990. Current status of isozyme gene symbols. RGN 7: 50-57.