Characterization and Selection of Phosphorus Deficiency Tolerant Rice Genotypes in Sri Lanka

Phosphorus(P) deficiency in soil is a major constrain for rice production. An important set of rice genotypes(landraces, old improved and new improved varieties) were screened for P deficiency tolerance in two major cropping seasons of Sri Lanka, in 2012. The Ultisol soil, which was collected from a plot cultivated with rice without fertilizer application for past 40 years(P_0) at the Rice Research and Development Institute(RRDI), Bathalagoda, Sri Lanka, was used as the potting medium for greenhouse trials. Two field trials were conducted in the same plots at RRDI. Both P_0 and P_(30)(30 mg/kg P_2O_5) conditions were used in the two greenhouse trials. At the early vegetative(three weeks after transplanting), late vegetative(six weeks after transplanting) and flowering stages, plant height and number of tillers per plant were recorded. At the flowering stage, shoots were harvested and shoot dry weight, shoot P concentration, shoot P uptake and P utilization efficiency were measured. All data were statistically analyzed using analysis of variance, regression and cluster procedures. The measured parameters were significantly different between P_0 and P_(30) conditions(P 0.05). Higher shoot dry weight was reported by the rice genotypes H4 and Marss under P_0 conditions. The regression analysis between shoot dry weight and P utilization efficiency revealed that the studied rice genotypes could be categorized to three P deficiency tolerance classes. A total of 13 genotypes could be considered as highly tolerant and 4 genotypes as sensitive for P deficiency. These results could be used to select parental genotypes for breeding and genetic studies and also to select interesting varieties or landraces for organic rice production.