The Fine Mapping Of A Major Phosphorus Utilization Efficiency QTL-Pup1

Low available phosphate(Pi)in acid soils is a major yield-limiting factor in crop production.The development of cultivars with improved ability to utilize Pi from soil becomes an important breeding program.A major QTL for Pi uptake(Pupl),mapped on the long arm of chromosome 12,was previously reported.A near-isogenic line designated as 515 was selected from a BC₆F₂ population developed from a cross between current parent Nipponbare and donor parent Kasalath.The phenotype performance under different Pi-supplied conditions and genomic background were investigated for the near-isogenic line.The results are summarized as follows:1.In field experiments with acid soil and low Pi level,we found that NIL-515 showed an advantage over Nipponbare with more tillers and larger dry weight.2.In solution culture experiments and pot experiments,NIL-515 also showed a superiority over Nipponbare under both high Pi and low Pi conditions.3.Genomic background analysis using 202 molecular markers indicates that NIL-515 is about 95%identical to Nipponbare.In addition to the Kasalath segment on chromosome 12 that includes the interval 54.5cM-61.6cM containing the putative QTL,NIL-515 contained 6 Kasalath segments on chromosomes 1,4, 7,9,10 and 11.4.To clean and narrow down Kasalath genomic background,we further backcrossed the NIL-515 with Nipponbare.By using molecular markers we developed,a new NIL(515-1)was isolated from 1000 BC₇F₂ population.The Kasalath genomic fragment on the putative Pupl region was narrow-down to 390kb.This NIL will be used for further analysis for the tolerance to low Pi stress.