Genetic analysis and fine mapping of phosphorus efficiency locus 1 (PE1) in soybean

Phosphorus (P) is required for crop production, particularly for soybean, due to its high protein and oil contents, and large demands for P in biological nitrogen fixation. Therefore, enhancing P efficiency is a practical and important target for soybean-breeding programs; however, the genetic mechanisms are still unclear. Previously, we identified a phosphorus efficiency locus 1 (PE1) in soybean through field evaluation. Here, fine mapping of PE1 was conducted in field using an expanded RIL population containing 168 F-9:11 families derived from the same parents, BX10 and BD2. A high-resolution genetic map covering a 67.39 cM genetic region in a similar to 20.1 M physical region was constructed using 117 bin markers from chromosome 11, and scaffolds-21 and -32. The results revealed that PE1 was comprised of 15 QTLs for 11 of 18 tested traits, all of which could be detected under both P-deficient and P-sufficient conditions. Through map-based cloning, PE1 was further delimited to a 200-kb region located on scaffold-32, where 16 candidate genes were predicted for the PE1 locus. A set of NILs were also evaluated in P-deficient field conditions, with the results that P content and grain yield were 27.9% and 74.8% higher, respectively, and 25.4% more P was allocated to reproductive tissues in pe1 than in PE1 plants. The results herein suggest that PE1 is a valuable locus underlying both P absorption and utilization efficiency, which may be directly applicable in breeding programs seeking to develop elite P-efficient soybean varieties.