Molecular Mapping of Soybean Aphid Resistance Genes in PI 567541B.

Soybean aphid (Aphis glycines Matsumura) is an important pest of soybean [Glycine max (L.) Merr.] in North America since it was first reported in 2000. PI 567541B is a newly discovered aphid resistance germplasm with early maturity characteristics. The objectives of this study were to map and validate the aphid resistance genes in PI 567541B using molecular markers. A mapping population of 228 recombinant inbred lines (RILs) derived from PI 567541B was investigated for the aphid resistance in both field and greenhouse trials. Two quantitative trait loci (QTLs) controlling the aphid resistance were found using the composite interval mapping method. PI 567541B conferred resistant alleles at both loci. An additive x additive interaction between these two QTLs was identified using the multiple interval mapping method. The two QTLs were localized on linkage group (LG) F and M, respectively. These two QTLs explained most of the phenotypic variation in both field and greenhouse trials. The QTL on LG M explained a large portion of the phenotypic variation. The QTL on LG F had much less effect than the one on LG M, especially in the greenhouse trial. These two QTLs were further validated using an independent RIL population. The effects of these two QTLs were also confirmed using 50 advanced breeding lines, which were all derived from PI 567541B, but had various genetic backgrounds. Hence, the two new QTLs identified and validated in this study could be useful in improving soybean aphid resistance by marker-assisted selection.