Inheritance of resistance and molecular mapping of soybean aphid resistance genes in soybean PI 567585A; identification of aphid resistance genes in soybean using modified nested association mapping (MNAM)

The soybean aphid, Aphis glycine (Matsumura), is a new major pest of soybean in the Midwest, including Michigan. Soybean PI 567585A has strong resistance to soybean aphids. The inheritance of aphid resistance in PI 567585A was determined by crossing with two susceptible soybean cultivars, Skylla and IA2070. The parents, F1, F2 plants and F 2:3 families were evaluated for aphid resistance in the field during the summer of 2008 and 2009. All F1 plants exhibited intermediate phenotypes to soybean aphids. The observed segregation ratios in the two F 2 populations, and F2:3 families fitted a segregation ratio 1:2:1. These data indicated that the aphid resistance in PI 567585A was controlled by one major co-dominant gene. Then, the genetic basis of aphid resistance in PI 567585A was determined. A mapping population of 158 F4:5 recombinant inbred lines (RILs) derived from the cross between PI 567585A and 'Skylla' was evaluated for aphid resistance in both greenhouse and field in 2009. A single aphid resistance gene was mapped in an interval between Satt674 and Sct_065 on linkage group J) using the composite interval mapping method. The locus explained 93.1% of the phenotypic variation in the field trial, and is located in the same genomic region as Rag3. This single aphid resistance gene in PI 567585A was confirmed in another F 3:4 RIL population derived from a cross between PI 567585A and IA2070.;PI 567598B was found to possess antibiosis resistance to the soybean aphid. A modified nested association mapping (MNAM) approach was used to locate resistance genes in PI 567598B on the integrated soybean linkage map. PI 567598B was crossed with 10 different susceptible cultivars to construct 10 recombinant inbred lines (RILs) populations. Genomic regions on linkage groups F, G, J and M were found associated with soybean aphid resistance in MNAM. Linkage analysis of a population of 94 BC1E4:5 RILs derived from PI 567598B and a F4:5 RIL population derived from E06902 were used to confirm the MNAM results. The results of linkage analysis showed that genomic regions on the linkage groups J, F and N were associated with aphid resistance.