Genetic Control of Root System Architecture in Rice

Abstract

An uncertain climate, paired with rapid human population growth, presents a major challenge to maintaining food security in the twenty-first century. Improvement of cultivation of rice, a primary source of calories for nearly half of the world’s people, provides a unique opportunity to address this challenge. As breeding in cereals has largely focused on aboveground phenotypes, root system traits represent potential unexplored targets for stress resilience and yield improvement. However, our understanding of the genetic control of root system architecture (RSA) in rice is fundamentally insufficient to contribute to these goals. The identification of novel rice RSA loci and the genes that underlie them could potentially provide breeders the tools to test the effect of root traits on water and nutrient usage. Our lab has developed a gel-based imaging and phenotyping system to facilitate genetic mapping of root traits in rice. Using this, we identify a mutation in a gene encoding a putative rice histidine kinase (OsHK1) that results in plants with increased seedling root depth. Using time-lapse imaging, we show that OsHK1 mutants have reduced circumnutation, or circular root tip growth. This supports a previously underappreciated link between RSA and the underlying pattern of root growth.