Grain size is measured in terms of either grain weight or shape, which includes grain length (GL) and grain width (GW). It is a critical component of crop yield and a significant trait for visual quality (Xing & Zhang, 2010). Different local cultures and cuisines prefer varying grain sizes. Grain size characteristics, immediately discernible to consumers, play a substantial role in defining market value (Fitzgerald et al., 2009; Lu et al., 2013). It has been reported that the QTL for seed width 5 (qSW5) is the most important QTL for grain width and grain weight, situated on chromosome 5 (Lu et al., 2013). Additionally, grain size 3 (GS3, orthologue to OsGS3) is one of the major QTLs located on chromosome 3 that regulates rice grain size (Fan et al., 2006; Takano-Kai et al., 2009; Kumar et al., 2016). GW5 is also a major QTL associated with rice grain width and weight (Weng et al., 2008; Dwivedi et al., 2019). qSW5, GS3, and GW5 are the primary determinants of grain size dimensions. Using the 1k RiCA mid-density genotyping panel for rice (Arbalaez et al., 2019), which includes the DarTSNPs GW3, GW5_1, and GW5_2 located on chromosomes 3 and 5, respectively, the Rice Biodiversity Center for Africa (RBCA) team conducted genotyping of 593 Oryza sp. accessions through DArTseq-based genotyping by sequencing (GBS) technology. The results enabled them to identify a subset of 38 accessions possessing the GS3 and GW5/qSW5 genes that control rice grain size. The accessions representing this mini collection come from 17 countries.