Identifying Quantitative Trait Loci Associated with Iron Deficiency Chlorosis in Soybean.

Sustainability of soybean production in the Northern Plain area has been challenged by iron deficiency chlorosis (IDC), a physiological problem with plants grown in high pH calcareous soil. This research aimed to identify quantitative trait loci (QTL) associated with the resistance to IDC in soybean. A recombinant inbreed line (RIL) population was developed from a cross between a cultivated (Glycine max) and a wild (G. soja) soybean line. A total of 201 RILs were grown in a field of calcareous soil (pH=8.5) on the campus farm in completely randomized block design with four replicates in summers of 2012 to 2014. Each replicate was visually evaluated for the degree of resistance to IDC in the 1-5 scale at three time points starting from the V3 stage. Heritability for the IDC resistance ranged from 0.26 to 0.71 at individual time points across the three years. A significant correlation (r=0.95) was observed between the visual scores and soluble iron (Fe²⁺) contents in newly developed leaves, indicating that the chlorosis was caused by lack of sufficient bioactive Fe in the photosynthetic tissue. A framework linkage map was constructed with 164 simple sequence repeat markers distributed on the 20 chromosomes and covers 2,156 cM of the soybean genome. A total of 11 QTL for resistance to IDC were detected on eight chromosomes across the three years, which contributed 6 to 13% of the phenotypic variances. Six of the loci were detected in more than one time point and one locus had the allele that enhanced the resistance to IDC from the wild parent. Seven of these QTL were also involved in digenic epistasis. This research revealed that wild soybean retained beneficial genes for the IDC resistance and provided additional information on candidate loci responsible for yield-limiting abiotic stress factor.