Genomics-Based Ideotype Breeding for Root System Architecture to Enhance Rice Production

The root system is an essential organ for taking up water and nutrients from the ground. Especially, adequate root system architecture (RSA) is important for plant growth under soil conditions where water and nutrients are deficient. The global climate change that has occurred in recent years has exacerbated the soil degradation. Based on this situation, genetic improvement of the RSA has been recognized as an important approach to enhance crop production. Root growth angle (RGA), which determines the direction of root elongation in the soil, affects the area in which roots capture water and nutrients.

Our group have isolated quantitative trait locus controlling RGA (DRO1) in rice. We also have developed a near-isogenic line (NIL) that carries a functional allele of DRO1 derived from the deep-rooting cultivar ‘Kinandang Patong’ in the genetic background of the shallow-rooting parent variety ‘IR64’, which has a non-functional allele of DRO1. Using this NIL, we demonstrated that introducing of RGA gene improved yield performance in rice under conditions of water and nitrogen deficiencies. Recently, our group isolated another QTL for RGA (qSOR1) in rice. We developed four NILs having functional or non-functional DRO1 and qSOR1. These lines showed shallower to deep roots, suggesting that we could develop wide natural variation of RSA by using only two QTLs. We identified several QTLs for root length because root length also determines the area in which roots take up water and nutrients. These QTLs will be useful genetic resources for ideotype breeding of RSA in the future.