Molecular Cloning Of Dro1, a Rice Quantitative Trait Locus That Controls Deep Rooting

Lowland rice (Oryza sativa L.), which is generally grown under flooded conditions, is susceptible to drought stress owing to its shallow root distribution and limited capacity to extract water from deep soil layers. Therefore, introducing deep rooting characteristics into lowland rice cultivars might be one way to improve their drought avoidance. However, the gene(s) responsible for deep rooting has not been identified in plants and it is still unclear whether it would affect drought avoidance. In this study, we cloned Deeper rooting 1 (Dro1), a rice quantitative trait locus controlling deep rooting, using mapping populations derived from a cross between IR64, a lowland rice with shallow roots, and Kinandang Patong, an upland rice with deep roots. To elucidate the role of Dro1 at the whole-plant level in a natural environment, we developed a near-isogenic line for Dro1 (Dro1-NIL) in the IR64 genetic background. The maximum root depth of IR64 and Dro1-NIL in upland conditions was ca. 20 and 45 cm, respectively. To clarify whether Dro1 improves drought avoidance, both lines were exposed to drought stress under upland conditions. The yield of Dro1-NIL was significantly higher than that of IR64, demonstrating that Dro1 contributes to drought avoidance in rice and that it can improve the productivity of rice under soil drought stress.