Identification of QTLs for phosphorus utilization efficiency in maize (Zea mays L.) across P levels

It is necessary to develop maize plants that are productive when grown in phosphorus (P) deficient soils because of the high cost of P supplementation in soils. The shoot phosphorus utilization efficiency, the whole phosphorus utilization efficiency of plant and root/shoot ratio as well as the quantitative trait loci associated with these traits were determined for a F-2:3 population derived from the cross of two contrasting maize (Zea mays L.) genotypes, 082 and Ye107. A total of 241 F-2:3 families were evaluated in replicated trials under deficient and normal phosphorus conditions in 2007 at Southwest University. The genetic map constructed by 275 SSR and 146 AFLP markers spanned 1,681.3 cM in length with an average interval of 3.84 cM between adjacent markers. Phosphorus was determined in harvested plants separated into two portions, roots and shoots with leaves. The sum of the two portions was used as an expression for P in the whole plant. By using composite interval mapping, a total of 5-8 distinct QTLs were identified under deficient and normal phosphorus, respectively. SPUE and WPUE under deficient phosphorus were controlled by one QTL, which was in the interval bnlg1518-bnlg1526 (bins 10.04) on chromosome 10. The loci of QTLs were same for SPUE, WPUE and RSR under normal phosphorus, which were in the interval bnlg1518-bnlg1526 (bins 10.04) and P2M8/a-bnlg1839 (bins10.07) on chromosome 10. Unlike regions conferring phosphorus utilization efficiency and root shoot ratio under normal phosphorus, the region under deficient phosphorus showed that genes controlling phosphorus utilization efficiency or root shoot ratio might be different. These results may be useful to breeding programs in marker assisted selections to identify phosphorus tolerant genotypes.