Linking Root Architecture and Function for Improved Rice Performance Under Drought Conditions.

Root architecture and hydraulic properties are key traits for exploiting the genotypic variation in rice response to drought. Novel field and greenhouse phenotyping approaches, including infrared thermography and spectral reflectance (NDVI), have made it possible to identify genotypes with improved water uptake under drought. Considerable genetic variation has been found among rice genetic stocks for root architecture traits under lowland field conditions. Deep root growth was associated with improved plant water status under reproductive-stage drought stress. Root length density at certain depths was negatively correlated with canopy temperature during drought stress, and positively correlated with soil water uptake as measured by frequency domain reflectometry. In addition to the spatial distribution of roots for improved water uptake, the ability of roots to take up and translocate water may also be a determining factor for a genotype’s resistance to drought. Biochemical and anatomical characteristics affecting root hydraulic conductance have been compared among genotypes contrasting for yield response to water deficit. Significant genetic variation has been observed in a number of advanced breeding lines, NILs, and genetic stocks for root attributes that may affect water uptake and root hydraulic conductance. These results integrating root architecture and root hydraulic properties are providing essential information towards a better understanding of dehydration avoidance mechanisms in rice. Such advancements in root drought physiology will be valuable for improving rice productivity under drought by dissecting target traits for breeding, and interpreting the genotype-by-environment interactions of drought resistance.