50. Phylogenetic study of cultivated rice and its wild relatives by RFLP

Plant Breeding Laboratory, Faculty of Agriculture, Kyushu University, Fukuoka, 812 Japan

To assess the phylogenetic affinity of cultivated rice (Oryza sativa L.) and the wild species, a total of 143 cultivated and wild strains were analyzed by RFLP technique and cluster analysis was subsequently performed based on the RFLP data.

Four kinds of restriction enzymes, BamHI, DraI, Eco RV and HindIII were used for digestion of plant genomic DNA and 24 rice genomic clones (2 clones per chromosome) mapped on RFLP map (Saito et al. 1991) were used for hybridization. Other methods for Southern analysis followed Saito et al. (1991). A total of 81 clone-enzyme combinations used for Southern analysis provided 399 fragments. Each fragment detected was treated as a unit character and the character was quantified by 1 for presence and 0 for absence of the fragment. Phylogenetic distances between strains were quantified based on Nei's formula (1990) and cluster analysis was done using the unweighted pair-group method with arithmetic mean (UPGMA, Sokal and Michener 1958).

The dendrogram produced by the cluster analysis is shown in Fig. 1. The complexes of 69 varieties of O. sativa and 62 accessions of O. rufipogon (including the annual forms) were classified into three distinct clusters (Clusters 1, 2 and 3 in Fig. 1). Cluster 1 (C1-W9) consisted of Japonica and Javanica varieties of O.

Fig. 1. Dendrogram showing phylogenetic relationships among a total of 143 strains of Oryza sativa and the wild relatives based on cluster analysis of RFLPS. Code number and the origin of each strain are shown in this figure. C1-13 are improved vareirties of O. sativa, C14-49; native varieties of O. sativa, F1-20; floating rice of O. sativa, C50; O. glaberrima, W1-39 and W51-73; O. rufipogon, and W40-50; O. meridionalis.

sativa and some accessions of O. rufipogon mainly come from China. Cluster 2 (C5-W25) consisted of Indica varieties of O. sativa and many accessions of O. riifipogon from different parts of Asia. Cluster 3 (W71-W31), probably a unique cluster, was composed of only the accessions of O. rufipogon mostly from India. O. meridionalis formed a distinct and isolated cluster (Cluster 4) from satival rufipogon complexes, indicating distant phylogenetic relationships against satival rufipogon complexes. An accession of O. glaberrima was not included in any of the four clusters.

Present analysis showed that sativa/rufipogon complexes had close affinity. However, there was a tendency that these two species formed the own small groups within each cluster. Cluster 1 and Cluster 2 apparently corresponded to Japonica and Indica rices, respectively. These data suggested that O. rufipogon had already been differentiated into two groups,corresponding to Japonica and Indica of O. sativa and O. sativa varieties were domesticated from different groups of O. rufipogon. This conclusion supports the hypothesis of Second (1982, 1985) and Morishima and Gadrinab(1987). Since this study apparently reflected phylogenetic relationships between sativa/rufipogon complexes and O. meridionalis, it would be possible by the same analysis to assess the other A genome Oryza spp., such as O. glumaepatula, O. longistaminata, O. glaberrima and O. barthii.

Morishima, B. and L.U. Gadrinab, 1987. Are the Asian common wild-rices differentiated into the Indica and Japonica types? Pages 11-20 in Crop Exploration and Utilization of Genetic Resources, Taichung District Agricultural Improvement Station, Taiwan.

Saito, A., M. Yano, N. Kishimoto, M. Nakagahra, A. Yoshimura, K. Saito, S. Kuhara, Y. Ukai, M. Kawase, T. Nagamine, S. Yoshimura, O. Ideta, R. Ohsawa, Y. Hayano, N. Iwata and M. Sugiura, 1991. Linkage map of restriction fragment length polymorphism loci in rice. Japan. J. Breed. 41: 665-670.

Second, G., 1982. Origin and genic diversity of cultivated rice (Oryza spp.): study of the polymorphism scored at 40 isozyme loci. Jpn. J. Genet. 57: 25-57.

Second, G., 1985. Evolutionary relationships in the Sativa group of Oryza based on isozyme data. Genet. Sel. Evol. 17: 89-114.

Sokal, R.R. and C.D. Michener, 1958. A statistical method evaluating systematic relationships. Sci. Bull., University of Kansas 38: 1409-1438.