A Rice Diversity Panel Evaluated for Genetic and Agro-Morphological Diversity between Subpopulations and its Geographic Distribution

A diverse collection of 409 Asian rice (Oryza sativa L.) accessions originating from 79 countries was fingerprinted with 36 simple sequence repeat (SSR) markers and evaluated for 18 agro-morphological traits. Genetically, the accessions clustered into five ancestral groups (subpopulations), indica, aus, aromatic (Group V), tropical japonica, and temperate japonica, based on model-based structure analysis. Thirty-three accessions with less than 60% ancestry from any single group were identified as admixtures. Canonical discriminant analysis identified eight agro-morphological traits (panicle number per plant, panicle length, plant height, flag leaf width, grain length, width, length: width ratio, and volume) as the main discriminatory characters among the rice accessions and between the subpopulations. Both SSR allele- and phenotypic trait-based analyses indicated a close relationship between aus and indica and similarly between temperate japonica and tropical japonica. The aromatic (Group V) rice represents a distinct small group that is more closely related to tropical japonica based on SSR alleles but to aus and indica based on phenotype. A strong relationship between subpopulations and geographical distribution was observed. This rice diversity panel with the accompanying genetic and phenotypic information provides a valuable foundation for association mapping, understanding the basis of both genotypic and phenotypic differences within and between subpopulations, and rice improvement programs.