Linking soil nutrient dynamics, plant concentration, and yield to identify phosphorous-efficient rice genotypes in South Florida

Rice (Oryza sativa L.) production on the organic-rich Histosols of South Florida faces persistent phosphorus (P) limitation, as much of the soil P becomes unavailable through reactions with iron and calcium compounds. Developing rice cultivars capable of maintaining high yields while conserving plant-available P is therefore critical for sustainable management of these soils. This study evaluated 45 rice genotypes, including 10 commercial cultivars and 35 experimental breeding lines, to understand how genetic variation influences soil P depletion, plant P uptake and distribution, and grain yield. Pre- and post-harvest soils were analyzed for Mehlich-3 P (M3P) and total P, and P concentrations were measured in roots, shoots, panicles, husks, and grains. Two physiological indicators, Relative Phosphorus Harvest Index (PHI) and Internal Efficiency of Grain P Use (IEgrain) were used to quantify P allocation and the conversion of grain P into yield. Results showed that all genotypes significantly depleted soil M3P (2.93-22.82 mg kg⁻¹; p 0.05) were observed between tissue P concentrations (root vs. shoot: r = 0.18; panicle vs. grain: r = -0.06). Avant- and Catahoula-derived lines showed high relative PHI but low IEgrain, suggesting efficient P translocation to grain but relatively lower yield. Hierarchical clustering identified genotypes 19T-218-87, 211L1293, 19T-218-42, 211L1227, 211L1228, Diamond, 19T-238-3, and RU1902207 as top performers combining high yield, efficient grain P allocation, and minimal soil P depletion, making them promising candidates for sustainable rice production on organic soils.