Progress Summary: The Objectives of this project are to genotype two populations, to phenotype them under P limited and P sufficient soil environments, and to identify genetic markers (Quantitative Trait Loci – QTL) associated with P uptake and P use efficiency. This research will deliver QTLs that can be used to accelerate breeding of soybean with greater P uptake and P use efficiency. During this funding period, the project progressed as planned. We have analyzed biomass P concentrations in plants from two different biparental mapping populations grown for two years under low and sufficient P conditions. We found significant genotypic variation in both populations in both low and sufficient P fertility treatments. The mean biomass P concentrations across two years for the two populations were 0.19 and 0.21 %P in low-P treatments and 0.25 and 0.26% in the sufficient P treatment. The genotypes at the high end of the phenotypic distribution had P concentrations that were 1.5 to 1.6 fold greater than those with low P concentration, with the relative difference in P concentrations staying within this range for both populations and in both low and sufficient P conditions. These results present a powerful dataset to identify genetic regions underpinning P use efficiency in soybean. The analyses to identify QTLs that condition the biomass P concentrations are ongoing. We have also received results for a large portion of the seed samples from the same two populations that were submitted to the analytical laboratory for P concentration analysis. Once the complete set of results are in hand for seeds, we will proceed with data analysis and QTL mapping for seed P concentration. The field experiment conducted in the 2024 season has been completed successfully. We have collected biomass samples as well as seed samples from nearly 2400 plots. These samples will be ground during the winter months and then submitted for P concentration determination. These data will be used to identify genomic regions that control soybean P uptake and use efficiencies.

This research will deliver QTLs that can be used to accelerate breeding of soybean with greater yields under low-P conditions and with greater P use efficiency in P-sufficient conditions. It also will provide information about P fertility management for P-tolerant lines. The outcomes of this project ultimately may reduce fertilization costs as P fertilizer applications can be reduced in low-P environments and less P is removed from the field per unit of yield. Reductions in P fertilizer applications will also increase sustainability as it will reduce potential negative environmental impacts by reducing the likelihood of P losses to water bodies.