Core Accession from PI 590403. The Core Collection containing about 10% of the whole NSGC Rice Collection was assembled by stratified random sampling method in 2002, evaluated comprehensively for 25 characteristics and proven to be highly representative of the whole collection. Information drawn from the Core Collection can effectively be used to assess the diversity of the whole collection with 88% certainty. A single plant was selected from each Core accession in 2006 and bulk seed from the single plant selection was produced in 2007 and deposited in the GSOR. DNA extracted from the selected plant was analyzed with one indel marker and 71 SSR (Single Sequence Repeat) markers that cover the entire rice genome about 30 cM apart. A Mini-Core Collection containing about 10% of the Core Collection was subsequently developed and genotyped through various means.Because the Core and Mini-Core were developed from single-plant selections from the NSGC accessions which may be phenotypically variable, there is the possibility that the GSOR seed sources are not exactly the same as the NSGC sources.