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.

Release of cytochrome c from mitochondria to the cytosol is a critical step in apoptotic cell death after focal cerebral ischemia. The relationship among cytochrome c release, selective vulnerability, and delayed death of hippocampal CA1 neurons after transient global ischemia was examined. Global ischemia was induced by 10 min of bilateral common carotid artery occlusion and hypotension in rats. Cytosolic expression of cytochrome c was evaluated by immunohistochemistry and Western blotting. Apoptosis after global ischemia was also characterized by terminal deoxynucleotidyl transferase-mediated uridine 5'-triphosphate-biotin nick end-labeling (TUNEL) staining and DNA gel electrophoresis. Immunohistochemistry showed cytosolic cytochrome c-positive cells exclusively in the CA1 subregion of the hippocampus as early as 2 hr after ischemia. Double fluorescent immunostaining confirmed that CA1 neurons and a small number of astrocytes expressed cytochrome c. Western blot analysis revealed a band (15 kDa) of cytochrome c in the cytosolic fraction and a corresponding decrease in the mitochondrial fraction. A significant number of TUNEL-positive cells appeared only in the CA1 pyramidal cell layer of the hippocampus, and DNA gel electrophoresis showed a significant amount of DNA fragmentation 3-5 d after ischemia. Our data provide the first evidence that cytochrome c was released to the cytosol from mitochondria in CA1 neurons after global ischemia and that the release preceded DNA fragmentation. These findings suggest cytochrome c involvement in the delayed death of hippocampal CA1 neurons in rats after transient global ischemia.

A mini core collection of Japanese rice landrace was developed based on a genome-wide SSR polymorphism survey of 236 accessions. The accessions used in the initial survey were selected based on the historical record and passport data from the collection maintained at the Genebank of the National Institute of Agrobiological Sciences (NIAS). These accessions were analyzed using 32 SSR markers. A total of 247 alleles were detected and the number of alleles per locus ranged from 3 to 15 (mean 7.7). Principal coordinate analysis using SSR data enabled classification of the accessions into three major groups, two Japonica groups and one Indica group. To develop a Japanese landrace mini core collection, the SSR data on the 236 accessions were subjected to cluster analysis and 50 groups were recognized at a similarity index of 0.88. A single accession from each of the 50 groups was selected. These 50 accessions retained 87.5% of the alleles detected in the original 236 accessions, and covered the variation of the initial set of accessions in terms of several agro-morphological traits.

The naturally occurring waxy and low-amylose variants of foxtail millet and other cereals, like rice and barley, originated in East and Southeast Asia under human selection for sticky foods. Mutations in the GBSS1 gene for granule-bound starch synthase 1 are known to be associated with these traits. We have analyzed the gene in foxtail millet, and found that, in this species, these traits were originated by multiple independent insertions of transposable elements and by subsequent secondary insertions into these elements or deletion of parts of the elements. The structural analysis of transposable elements inserted in the GBSS1 gene revealed that the non-waxy was converted to the low-amylose phenotype once, while shifts from non-waxy to waxy occurred three times, from low amylose to waxy once and from waxy to low amylose once. The present results, and the geographical distribution of different waxy molecular types, strongly suggest that these types originated independently and were dispersed into their current distribution areas. The patterns of GBSS1 variation revealed here suggest that foxtail millet may serve as a key to solving the mystery of the origin of waxy-type cereals in Asia. The GBSS1 gene in foxtail millet provides a new example of the evolution of a gene involved in the processes of domestication and its post-domestication fate under the influence of human selection.

Assessment and utilization of diversity in plant genetic resources is vital for the improvement of plant species. A sorghum diversity research set (SDRS) was developed by using SSR markers. A total of 320 sorghum accessions were selected based on geographic distribution from more than 3,500 germplasm accessions comprising Asia (East, Southeast, South and Southwest Asia) and Africa, conserved at NIAS Genebank, Japan. We selected 38 simple sequence repeats (SSR) markers which generated 146 alleles, covering ten chromosomes of sorghum from a three different published SSR linkage map of sorghum. The average percentage of polymorphic loci (P) and gene diversity (He) observed in this study were 82.8 and 0.217 respectively. Analysis showed a positive correlation with geographic pattern of differentiation. Based on SSR assessment, 107 sorghum accessions were selected as diversity research set. There was no significant difference in pattern of genetic spectrum between SDRS and base population. Similarly no greater change was observed for variability parameters (Dice, %P, He) and almost all of the SSR alleles were retained in selected sorghum accessions except for the loss of a single allele at locus Xtxp287. SDRS was sown during sorghum sowing season in two replications. Data were recorded on 26 important morphological traits according to the standard sorghum descriptors at Genebank. Analysis of variance showed a highly significant difference among all accessions for all of the traits. Morpho-agronomic traits could not effectively classify the accessions according to geographic origin by using cluster analysis.