Comparative Morphophysiological Analyses and Molecular Profiling Reveal ‘Pi-Efficient Strategies’ of a Traditional Rice Genotypefor Low Phosphorus Tolerance in Traditional indica Rice. Oryza sativa

Phosphate (Pi) deficiency severely affects crop yield. Modern high yielding rice genotypes are sensitive to Pi deficiency whereas traditional rice cultivars are naturally compatible to low Pi ecosystems. However, the underlying molecular mechanisms for low Pi tolerance in traditional genotypes remain largely elusive. To delineate the molecular mechanisms for low Pi tolerance, two contrasting rice genotypes - Dular (low Pi tolerant) and PB1 (low Pi sensitive) - have been selected. Comparative morphophysiological, global transcriptome and lipidome analyses of root and shoot tissues of both genotypes raised under Pi deficient and sufficient conditions revealed the potential low Pi tolerance mechanisms of traditional genotype. Most of the genes associated with enhanced internal Pi utilization (phospholipid remobilization) and modulation of root system architecture (RSA) are highly induced in traditional rice genotype, Dular. Higher reserve of phospholipid and greater accumulation of galactolipids under low Pi in Dular indicated its better internal Pi utilization. Furthermore, Dular also maintained better root growth than PB1 under low Pi resulting in larger root surface area due to increased lateral root density and root hair length. Genes involved in enhanced low Pi tolerance of traditional genotype can be exploited to improve the low Pi tolerance of modern high yielding rice cultivars. Overall design: 15-days-old Root and shoot tissue of rice seedlings (variety: Dular and PB1) grown under Phosphorus deficient conditions were compared with corresponding Phosphorus sufficient conditions