Résumé
Future rice (Oryza sativa) crops will likely experience a range of growth conditions, and root architectural plasticity will be an
important characteristic to confer adaptability across variable environments. In this study, the relationship between root architectural
plasticity and adaptability (i.e. yield stability) was evaluated in two traditional 3 improved rice populations (Aus 276 3 MTU1010
and Kali Aus 3 MTU1010). Forty contrasting genotypes were grown in direct-seeded upland and transplanted lowland conditions
with drought and drought + rewatered stress treatments in lysimeter and field studies and a low-phosphorus stress treatment in a
Rhizoscope study. Relationships among root architectural plasticity for root dry weight, root length density, and percentage lateral
roots with yield stability were identified. Selected genotypes that showed high yield stability also showed a high degree of root
plasticity in response to both drought and low phosphorus. The two populations varied in the soil depth effect on root architectural
plasticity traits, none of which resulted in reduced grain yield. Root architectural plasticity traits were related to 13 (Aus
276 population) and 21 (Kali Aus population) genetic loci, which were contributed by both the traditional donor parents and
MTU1010. Three genomic loci were identified as hot spots with multiple root architectural plasticity traits in both populations,
and one locus for both root architectural plasticity and grain yield was detected. These results suggest an important role of root
architectural plasticity across future rice crop conditions and provide a starting point for marker-assisted selection for plasticity.