D. Research Notes

I. Varietal Differentiation and Evolution

1. Fingerprinting of Korean commercial japonica rice cultivars based on AFLP analysis

Y.C.CHO1, G.B. GREGORIO2, K.H. KANG1, S.N. AHN1, D.S. BRAR2 and H.P. MOON1
1) National Crop Experiincnl Station, RDA, Suwon. 441-100 Rep. of Korea
2) International Rice Research Institute, P.O. Box 933, 1099 Manila, Philippines

Recently developed, RFLP analysis (Cho et al. 1995; Wang and Tanksley 1989) and PCR-based technique, RAPD analysis (Ahn et al. 1996; Mackill 1995) have been widely adopted to classification of rice germplasm. These techniques were not efficient in fingerprinting studies among japonica rice cultivars having low polymorphism. The japonica cultivars are predominantly grown in temperate regions in Korea, Japan, some regions of China, California in USA, and so on. This study was undertaken to evaluate the efficiency of fingerprinting among japonica cultivars of relatively close relationship by AFLP analysis.

AFLP technique is based on the selective PCR amplification of restriction fragments from a total digest of genomic DNA. AFLP analysis was carried out by using the method of Vos et al. ( 1996) with some modifications and EcoRI/MseI restriction enzyme combination (Cho et al. 1997). The number of bands for each primer pair ranged from 34 to 92 with an average of 68.3 per reaction and the polymorphic bands from 10 to 39 with an average of 21.4. These results were similar to those of Mackill et al. (1995) and Vos et al. (1996). Genetic similarities among 27 japonica rice cultivars by Nei's formular (1987) were 0.819-0.986. Cluster analysis was performed using UPGMA (Sokal and Michener 1958) based on AFLP polymorphisms (Fig. 1). All cultivars revealed a distinct fingerprint at least within 84.5% genetic similarity. Two Korean cultivars, Sobaegbyeo and Odaebyeo derived from the cross Akitsuho/Fuji 269 of Japanese cultivars, clustered together with their parents. Samnambyeo and Hwaseongbyeo also clustered with their parents, Fuji 280 and BL 1. High quality cultivar Ilpumbyeo grouped with its parent Inabawase, and Japanese high grain quality cultivars, Koshihikari and Kinuhikari. Two Korean cultivars (Jinmibyeo, Tamjinbyeo) and three U.S. cultivars (S-202, M-202, M-401) were weakly clustered with the main group, respectively.

The first breeding goal of rice in Korea has been changed to grain quality together with the elevation of the living standard since the middle of 1980s. During that time, about one hundred japonica rice cultivars have been developed for farmers in Korea. Most Korean japonica commercial rice cultivars were developed from the crosses among some japonica high quality cultivars of Japan, because Korean is similar to Japanese for the liking of rice grain quality (Table 1). So, genetic diversity of modern Korean japonica rice cultivars has been reduced due to intensive breeding efforts to develop the varieties of high yield, high grain quality, and disease and insect resistance (Kim et al. 1994). Although the average percent polymorphism of AFLP markers was not higher than those of RAPD and microsatellite within japonica cultivars (Mackill et al. 1995), it seems that AFLP analysis will be efficiently used to fingerprint among rice germplasm including japonica cultivars having low genetic diversity because the number of polymorphic bands was much higher per gel.

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References 

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Cho, Y.C., G.B. Gregorio, K.H. Kang, S.N. Ahn, D.S. Brar and H.P. Moon, 1997. Classification and genetic >diversity analysis of 48 commercial varieties in rice (0ryza sativa L.) based on AFLP. Korean J. Breed.29 (Suppl. 1 ): 84-85.

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