Research progress on the divergence and genetic basis of agronomic traits in xian and geng rice

The Asian cultivated rice Oryza sativa can be classified into two major subspecies: japonica/geng and indica/xian. There are large physiological and phenotypic differences between the two subspecies, with each having its advantages and disadvantages. Understanding the differences between xian and geng could provide a foundation for cultivar improvement based on hybridization between subspecies in order to synthesize favorable traits. We review the origin and domestication of xian and geng rice, compare their differences in terms of physiological and phenotypical traits, and describe the molecular mechanism differences between the subspecies. Based on this knowledge, we propose an ideal plant architecture of geng rice varieties for northern regions.