Fine-Mapping, Physiological Evaluation, and Candidate Gene Exploration of an Iron Deficiency Chlorosis Tolerance Locus in Soybean

Abstract

Iron Deficiency Chlorosis (IDC) can be a significant yield limiting nutrient stress in soybean. IDC most frequently occurs in high pH soils that are rich in calcium carbonates, as is common in areas of the Midwestern United States. While several agronomic solutions exist to combat IDC, such as the application of iron chelates at planting, the use of tolerant soybean genotypes remains the most effective method of controlling IDC stress. Breeding for IDC tolerance is common, however little about the genetics of IDC is understood, aside from a major tolerance locus located on Gm03. A tolerance locus was previously discovered through bi-parental and association mapping on Gm05 to a 1.5 megabase region, which in this study was found to be important in elite soybean germplasm and warranted further investigation. Fine-mapping was conducted using heterogeneous inbred families, narrowing the interval to 137 kilobases and 17 genes. A controlled environment assay was developed to analyze the effect of nodulation, pH, and calcium carbonates on soybean genotypes and to assess the expression of Glyma.05g001700, a gene candidate in the fine-mapped region. Glyma.05g001700 was further explored using protein modeling, domain classification, gene homology, haplotype diversity, and overexpression in soybean hairy roots to assess gene function. It was concluded that Glyma.05g001700 is likely involved in iron homeostasis through changes in gene expression driven by a putative TATA box present in the tolerant genotype ‘Fiskeby III’.