The aus rice variety group originated in stress-prone regions and is a promising source for the development of new stress-tolerant rice cultivars. In this study, an aus panel (~220 genotypes) was evaluated in field trials under well-watered and drought conditions and in the greenhouse (basket, herbicide and lysimeter studies) to investigate relationships between grain yield and root architecture, and to identify component root traits behind the composite trait of deep root growth. In the field trials, high and stable grain yield was positively related to high and stable deep root growth (r = 0.16), which may indicate response to within-season soil moisture fluctuations (i.e., plasticity). When dissecting component traits related to deep root growth (including angle, elongation and branching), the number of nodal roots classified as 'large-diameter' was positively related to deep root growth (r = 0.24), and showed the highest number of colocated genome-wide association study (GWAS) peaks with grain yield under drought. The role of large-diameter nodal roots in deep root growth may be related to their branching potential. Two candidate loci that colocated for yield and root traits were identified that showed distinct haplotype distributions between contrasting yield/stability groups and could be good candidates to contribute to rice improvement.
We thank L. Holongbayan, N. Turingan, N. Driz, A. Los Añes, N. Sadiasa, A. Reyes, D. Morales, P. Zambrano, T. Batoto, E. Mico, L. Satioquia, M. Manalili and C.A. Centeno for technical support. We also acknowledge R. Serraj for initiating the aus field trials, M. Wissuwa and J.G. Monroe for contributions to the 2018 field trial, J. Xu and D. Pisano for advice on statistical analysis, Y. Uga for advice on the basket study and I. Ajmera for helpful discussions about nodal roots. This study was supported by the Generation Challenge Program (GCP) project G3008.06, 'Targeting Drought-Avoidance Root Traits to Enhance Rice Productivity under Water-Limited Environments'. Q. Liao was supported by the Chinese Scholarship Council (CSC) and 'Hengygang Guiding Plan Project 2020jh022798' award. M. S. Islam was supported by a Bangabandhu Fellowship on Science and ICT from the Ministry of Science and Technology, Bangladesh.
- Chromosome Mapping
- Edible Grain
- Genome-Wide Association Study