Inheritance and Molecular Mapping of Soybean Aphid Resistance in Soybean Germplasm Accession PI 603432B

Soybean aphid (Aphis glycines Matsumura) has been found colonizing soybean (Glycine max (L.) Merr.) plants in the upper Midwestern United States since 2000. Genetic characterization of resistance to soybean aphids helps to develop new resistant cultivars to protect soybean production from pest damage. The objective of this study is to analyze the inheritance of soybean aphid resistance in the soybean germplasm accession PI 603432B, and to map the location of the resistance gene(s). Two populations were formed by crossing the resistant PI 603423B with two susceptible varieties (MN0602CN and MN0081). The F2 plants and F2:4 lines from each cross were screened for aphid resistance in the field and greenhouse. The segregation for aphid resistance in the F2 and F2:4 populations derived from both crosses appeared to fit a single dominant gene model in inheritance. To determine whether the PI 603432B has the same gene(s) as those previously identified in other germplasm lines (plant introductions, PIs), 12 simple sequence repeat (SSR) markers which were previously reported to be associated with soybean aphid resistance were screened using bulk segregate analysis (BSA). The data from the SSR marker screening indicated that PI 603432B carried the same or similar gene as resistance gene Rag2 identified in PI 243540. The gene/QTL was mapped to a region on the linkage group F between SSR markers Sct_033 and Satt510. This information will be useful to facilitate breeding for aphid resistance in soybean