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A rice diversity research set of germplasm (RDRS) was developed based on a genome-wide RFLP polymorphism survey of 332 accessions of cultivated rice (Oryza sativa L.). The accessions used in the initial survey were selected based on the passport data from the whole collection maintained at the Genebank of the National Institute of Agrobiological Sciences (NIAS). These accessions were analyzed using 179 nuclear RFLP markers. A total of 554 alleles were detected, and the number of alleles per locus ranged from 2 to 8 (mean 3.1). Principal coordinate analysis using RFLP data enabled to classify the accessions into three major groups, one Japonica and other two Indica. To develop a rice diversity research set of germplasm, the RFLP data on the 332 accessions were subjected to cluster analysis and 67 groups were recognized at a similarity index of 0.915. A single accession from each of the 67 groups was selected. These 67 accessions retained 91% of the alleles detected in the original 332 accessions, and covered the variation of the initial set of accessions in terms of several agro-morphological traits. The 69 accessions including varieties from 19 countries and the reference varieties, Nipponbare and Kasalath, were selected for the development of a rice diversity research set of germplasm. This collection which is presently well characterized at the molecular level will be used for the detailed genetic studies and rice improvement.
Kojima et al. (Sat,) studied this question.