Mapping QTLs for Phosphorus-Deficiency Tolerance at Wheat Seedling Stage

Soil phosphorus (P) deficiency is one of the major limiting factors to crop production throughout the world. It is an important strategy to breed varieties with improved P-deficiency tolerance for sustainable agriculture. The objective of this study was to map QTLs for P-deficiency tolerance in wheat, and develop molecular marker assisted selection in breeding wheat with improved P-deficiency tolerance. A doubled haploid (DH) population, consisting of 92 DH lines (DHLs) derived from P-deficiency tolerant wheat variety Lovrin 10 and P-deficiency sensitive variety Chinese Spring, was developed for mapping QTLs for P-deficiency tolerance. A genetic linkage map consisting of 34 linkage groups was constructed using 253 SSR markers. Shoot dry weight (SDW), tiller number (TN), shoot P uptake (SPU), and shoot P utilization efficiency (PUE) were investigated at seedling stage under P deficiency (−P) and sufficiency (+P) condition in two pot trials in 2002 and 2003, respectively. All traits segregated continuously in the population under either −P or +P condition. Significant positive correlations were found in between TN, SDW and SPU, whereas significant negative correlations were observed between PUE and SPU and between PUE and TN. Twenty and 19 QTLs were detected under −P and +P condition, respectively. The 39 QTLs were distributed on 21 chromosomal regions. There were three clusters of QTLs, which were associated with Xgwm25l (on chromosomes 4B), Xgwm271.2 (on chromosome 5A), and Xgwm121 (on chromosome 5D), respectively. Compared to the DHLs with all Chinese Spring alleles at the three loci, those with all Lovrin 10 alleles had, on average, much higher SPU, SDW and TN under −P condition in both trials, suggesting the importance of the three loci in controlling P-deficiency tolerance. It was interesting to find that two of the above three loci were closely linked with vernalization requirement genes VRN-A1 (on chromosome 5A) and VRN-D1 (on chromosome 5D). Potential implication of the linkage between P-deficiency tolerance and VRN genes was discussed.