|Vol. 18 >C. Research Notes> I. Varietal differentiation and evolution|
|1.||Evaluation of upland rice genetic resources in northern Laos|
|S.YAMANAKA1,2, R. ISHIKAWA3, Y. FUKUTA4,
I. NAKAMURA5, T. SATO6 and Y.-I. SATO2
1)The United Graduate School of Agricultural Science, Gifu University, Gifu, 501-1193 Japan
2)Faculty of Agriculture, Shizuoka University, Shizuoka, 422-8529 Japan
3)Faculty of Agriculture and Life Science, Hirosaki University, Hirosaki, 036-8561 Japan
4)Plant Breeding, Genetics and Biochemistry Division, International Rice Research Institute, DAPO BOX 7777, Metro Manila, Philippines
5)Graduate School of Science and Technology, Chiba University, Matsudo, 271-0092 Japan
6)Graduate School of Life Science, Tohoku University, Sendai, 980-8577 Japan
We investigated upland rice genetic resources in northern Laos, where
traditional upland rice cultivars are frequently grown under slash-and-burn
field. At present, traditional upland rice cultivars are on the verge
of genetic erosion because of replacement by modern improved cultivars,
which are promoted to reduce the slash-and-burn upland fields (Sato 1994).
Hence, we are in a hurry to collect, evaluate and conserve these genetic
types. It was suggested that these four strains were resultant of natural hybridization between japonica and indica strains, and the direction of geneflow was mainly from indica to japonica because of a relatively low selfing rate of japonica Outcross-pollination has occurred and segregated in slash-and-burn upland fields. Cultivated rice is generally self-pollinated, how- ever about 1 percent cross-pollination could be occurred naturally (Morishima et al. 1992). Hybrids that naturally occurred by cross-pollination between strains could be the source of intermediate strains found in slash-and-burn fields of these areas.
A previous study conducted in these areas did not focused on nuclear-cytoplasm combination (Roder et al. 1996). Here, we presented that such information, which are important to evaluate genetic resources and describe current status of upland rice cultivation.
Ishikawa, R., K. Maeda, T. Harada, M. Niizeki and K.Saito, 1991. Classification of Japanese rice varieties into Indica and Japonica types by using isozyme genotypes. Jpn. J. Breed. 41: 605-622.
Kanno, A., N. Watanabe, I. Nakamura and A. Hirai, 1993. Variations in chloroplast DNA from rice (Oryza sativa): differences between deletions mediated by short direct-repeat sequences within a single species. Theor. Appl. Genet. 86: 579-584.
Morishima, H., Y. Sano and H.-I. Oka, 1992. Evolutionary studies in cultivated rice and its wild relatives. Oxford Surveys in Evolutionary Biology 8: 135-184.
Roder, W., B. Keoboulapha, K. Vannalath and B. Phouaravanh, 1996. Glutinous rice and its importance for hill farmers in Laos. Econ. Bot. 50: 401-408.
Sato,Y.-I., 1994. Genetic erosion in the tropics. Tropics 3: 33-50.
|Vol. 18>C. Research Notes> I. Varietal differentiation and evolution|