We obtained two genomic DNA fragments of indica rice cultivar Culture 340. These clones hybridized with DNA of indica and some of the javanica cultivars, but not with japonica cultivars.

More than 500 Culture 340 DNA fragments were used to find out the one, which did not hybridize to Aikoku (japonica cultivar) DNA. Consequently, we obtained two DNA clones, G93 and G318, which originated from the Culture 340 genomic DNA digested with Eco Rl and Pst I, respectively. In Culture 340, genomic hybridization showed multiple bands when hybridized with G93, while G318 showed single band.

To see the specificity of hybridization with these probes, nine indica (Paddy type 52, P.T.B.7, P.T.B.10, He-you-zao, Yin-nian 35, Padi raoekang, 70a Som cau, Bai-ke and Duan-guang-ha-luo), five javanica (Nabeshi, Qu-jing-xiao-hong-diao, Inakupa, Ga-rumbalay and Ase larre) and four japonica (Xiao-bai dao, Nagaewase, Taichung 65 and Kissin) cultivars were used for Southern blot analysis. DNAs from these cultivars were digested with Eco Rl, and hybridized with G93 as a probe. The autoradiogram showed multiple bands in all indica and three javanica cultivars. A 1.7kb fragment was common among these cultivars. When DNA clone G318 was used as a probe, single band (4.2kb) was detected in all indica and two javanica cultivars. Both probes detected no band in the four japonica cultivars used in this analysis.

Southern analysis using G93 and G318 can be used to classify the indica and japonica type cultivars. Null alleles in japonica indicated that japonica genomes have no homologous regions to the two DNA clones. Polymorphism in javanica cultivars with respect to presence or absence of these homologous sequences may indicate introgression of genes from indica to javanica cultivars because javanica cultivars generally co-exist with indica and/or japonica cultivars in their growing areas.

Such DNA probe as presented in this report would be useful to understand genetic diversity of rice plants (Kochko et a/.1991; Nakagahara 1978: Second 1982; Zhang et al. 1992; Zhao et al. 1989).

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