Confirmation and characterization of a major QTL for P uptake in rice

Abstract

Previously four quantitative trait loci (QTLs) for P uptake had been identified in a rice population developed from a cross between the indica landrace Kasalath (high P uptake) and the japonica cultivar Nipponbare (low P uptake). One QTL linked to marker C443 on chromosome 12 had a major effect. A near isogenic line (NIL-C443) for QTL C443 was developed that genetically resembled Nipponbare to 91% but carried the chromosomal segment from Kasalath at the QTL. To further characterize QTL C443, a pot experiment on P deficient soil was conducted and whole plants sampled 40, 70, 100, and 150 days after sowing. Under P-deficiency NIL-C443 had four times the P uptake of Nipponbare whereas both were similar with optimum P supply. QTL C443 therefore affects mechanisms specifically increasing P uptake under P deficiency. The root surface area of NIL-C443 increased 7-fold between days 40 and 150, whereas roots of Nipponbare less than doubled in size and only reached 15% of their non-stress surface area. The superior P uptake of NIL-C443 was therefore caused by the ability to maintain root growth under P deficiency. Potential mechanisms responsible for that ability are discussed..