K. S. CHENG1, Y. Z. CHANG1, X. K. WANG2 and H. W. CAI2
1) Yunnan Academy of Agricultural Sciences, Kunming, 650205 China
2) Beijing Agricultural University, Beijing, 100094 China
It was postulated by Ting (1957) that the Keng (Japonica) rice was derived from the Hsien (Indica) rice. H. I. Oka and K. S. Cheng, however, postulated in their experiments respectively that the common wild rice (Oryza rufipogon) was potential to evolve both Hsien and Keng types. Wang et al. (1984) advocated further that the Keng rice originated probably from wild progenitors domesticated in upland conditions. A few new findings in this relation will be reported in this paper.
The senior author discovered in 1985 that a variety named Matia Aman 53-13 (IRRI Acc. no. 37764) was of the Keng type, although the Aman rice was generally believed to belong to subspecies hsien (indica). After a few years, we came into contact with more Aman varieties through the courtesy of the IRRI. On examination of 10 entries, we found three of them were Japonicas morphologically and one was Japonica-like or "Keng-cline" in our terminology. The three entries bear the name Dhala Aman with accession numbers from 32866 to 32868. They differ somewhat in phenol reaction from negative to faintly tinted and also differ slightly in esterase isozymograms. It is interesting to see that all of them, including the Keng-like Awasina Aman (Acc. no. 37360) carry an esterase band characterizing the Asian common wild rice. On the other hand, bands characterizing the Hsien and Keng types have not been found among them, although one or two auxiliary discriminating bands may be met with; these features are also the characteristics of many wild rices. In cultivated rice so far investigated, a similar pattern has been encountered also in Ma-ke-da-he-zi, a late Keng rice from Jiang-xi, where the wild rice still persists.
Another example is presented by Hakoda et al. (1990). They found some deepwater rice in Burma, India, Bangladesh and Indonesia were very akin to the Keng type by isozyme analysis. Dr. H. Morishima, on her visit to Yunnan, brought to us four deepwater rices from Burma. We found that two of them (Taungdi and Yemanine) were Keng types in seed characters, and in isozymes as given by her.
The above evidence strongly suggests that the Keng rice evolved directly from the common wild rice. It is well known that the habitat of deepwater rice and Aman in South Asia is comparable to that of the wild rice. They are all photosensitive and mature in early winter when the temperature becomes low. Through the courtesy of Dr. Morishima, we have three broadcast Amans, Gowai, Lalaman and Khesail. All of them are like Keng types too.
We are inclined to assume that the declining temperature regime induces the differentiation, although the seasonal difference in temperature is not so great as one would expect. Taking into consideration the fact that in Indonesia where the day-length is nearly constant throughout the year, some Indica cultivars are photosensitive as well as those from other regions where day-length changes seasonally, the above hypothesis may not appear so improbable. An investigation on the accumulative effect of the trend of small gradual changes in temperature and day-length may throw some more light on this problem.
Hakoda, H., Jun Inouye and H. Morishima, 1990. Isozyme diversity found among Asian deep- water rices. RGN 7: 91-93.
Ting, T., 1957. The origin and evolution of cultivated rice in China. Acta Agron. Sinica 8(3): 243-260. (in Chinese)
Wang, X. K., K. S. Cheng, Y. X. Lu, J. Luo, N. W. Huang and G. R. Liu, 1984. Studies on indigenous rice in Yunnan and their utilization, III. Glabrous rice in Yunnan. Acta Univ. Agric. Pekinensis 10(4): 333-344. (in Chinese)