Root Characterization of Myanmar Upland and Lowland Rice in Relation to Agronomic and Physiological Traits under Drought Stress Condition

Lowland and upland rice are the two most important rice ecotypes and are grown under different ecosystems of contrasting soil water conditions. The study aimed to characterize root morphological, anatomical, and architectural traits and shoot physiological traits related to agronomic traits in Myanmar lowland and upland rice under drought conditions. Drought experiments were conducted in the field and in the greenhouse. The reduction in root traits under drought was observed in both lowland and upland rice except for the stele and xylem area. Stele area and xylem area were increased under drought in lowland rice while stele area in upland rice was decreased and was not changed in the xylem area. A positive relationship between agronomic traits and root traits of lowland rice was observed including the total number of nodal roots, root number per tiller, and a negative relationship in lateral root density more than anatomical traits. While upland rice illustrated the relationship between root anatomical traits and agronomic traits. In addition, a negative contribution to biomass by photosynthesis rate, stomatal conductance, and transpiration rate was observed in lowland and upland rice. These findings can help improve drought tolerance in rice by selecting the optimal root trait for each rice ecosystem.