9. Two SDS-PAGE protein bands specific to subspecies indica and japonica of rice

Varieties of Oryza sativa L. are divided into subspecies indica and japonica on the basis of certain morphological and physiological characters. The two types differ in geographical distribution and show varying degrees of F1 sterility in their crosses. Because of overlapping character variations, there is no absolute criterion for their distinction (Morishima and Oka 1981).

Spikelets at an early developmental stage were used as material in the present study. The SDS-PAGE (sodium dodecyl sulfate-polyacrylamide gel electrophoresis) and silver staining protein patterns were examined in four indica (Nanxiongzao, Zao-jinfeng, Ma-weiqi and Zhongshan-gounian), three japonica (Fengerliu, Fengjin and Ri-bengqing) and four varieties showing F1 fertility with both indica and japonica testers (Ketan nangka, Calotoc, CPSLO-17 and 02428; the last one is a japonica and the other three are so-called Javanica; "wide compatibility varieties" according to Ikehashi and Araki 1986 and Araki et al. 1986). The indica

Fig. 1. Two specific "marker" bands of subspecies indica and japonica appearing in SDS-PAGE protein patterns, shown by arrows. Lane 1-4: so-called Javanica varieties, lane 5-8:indica varieties, lanes 9-11:japonica varieties.

varieties manifested a 111 Kd band, but the japonica varieties did not show it. On the other hand, the three japonica varieties exhibited a 106 Kd band which did not appear in indica varieties. These two specific bands could be seen clearly only when staining technique was suitable, because they and their adjacent bands easily overlapped (Fig. 1). Using Blum's (1987) staining technique, the bands in question were gray to dim blue and the adjacent bands appeared dark brown.

We have examined the occurrence of the two specific bands in F1 plants from indica/japonica crosses (Chengte 232 X 26 Zalzao and Taipei 8 X Er jinqing). The results showed that both the bands were dominant and appeared in the F1 hybrids as in the parental lines. The two bands also appeared in some Javanica varieties. The SDS-PAGE patterns of Ketan nangka and Calotoc were similar to that of japonica (Fig. 1, lanes 1 and 2), but the pattern of CPSLO-17 was similar to that of indica (Fig. 1, lane 3). Further studies are being conducted to characterize the two specific-band proteins.

This work was supported by grants from National Program 863 of P. R. China and from the Rockefeller Foundation.

Araki, H., K. Toya and H. Ikehashi, 1986. Role of wide compatibility genes in hybrid rice breeding. Intern. Symp. on Hybrid Rice. Changsha, China.

Blum, H., 1987. Improved silver staining of plant proteins, RNA and DNA in polyacrylamide gels. Electrophoresis 8: 93-99.

Ikehashi, H. and H. Araki, 1986. Genetics of F1 sterility in remote crosses of rice. In IRRI (ed.), Rice Genetics, p. 119-130. IRRI, Manila.

Morishima, H. and H. 1. Oka, 1981. Phylogenetic differentiation of cultivated rice, 22. Numerical evaluation of the Indica-Japonica differentiation. Jpn. J. Breed. 31: 402-413.