Rice seedling tolerance to phosphorus stress in solution culture and soil

Five rice genotypes with different performance under P-stress condition were tested in both a soil pot experiment and a solution culture experiment under different P supply conditions to evaluate rice performance to P stress. The relative parameters, defined as a ratio of the parameters measured under P stress condition to the parameters measured under P sufficient condition, were used to evaluate the genotypic variation in tolerance. It was found that relative tillering ability (RTA), relative root number (RRN) and relative root length (RRL), based on ratio of the measurements at 1 ppm P level to these at 10 ppm P level in solution culture after 2-week growth, could be used to assess the genotypic tolerance to P stress in terms of P uptake ability and biomass production under P stress condition. Relative P uptake ability (RPUP) and relative P use efficiency (RPUE) were relatively independent parameters with each other, and no parameters from solution culture were found to be significantly correlated with RPUE under soil condition. The result indicates that a ratio of tiller number measured at 1 ppm P to that measured at 10 ppm P after two weeks growth under solution culture condition may be used as a simple and reliable screening parameter for rice tolerance to P stress.