LAUSR

The soybean aphid (Aphis glycines Matsumura) is a pest of soybean (Glycine max (L.) Merr.) in many soybean-growing countries of the world, mainly in Asia and North America. While numerous aphid-resistance loci have been mapped, new and virulent aphid biotypes continue to be identified. PI 606390A confers resistance to all four characterized soybean aphid biotypes. The objectives of this study were to identify single nucleotide polymorphism (SNP) markers closely linked to the loci conferring resistance to soybean aphid biotypes 3 and 4. One hundred and eight F6:7 families from a cross between the susceptible experimental line HR09-018 and the resistant PI 606390A plus the two parental lines were screened with aphid biotypes 3 and 4 using greenhouse choice tests. Broad-sense heritability estimates ranged from 0.69 to 0.91. Correlation between biotype 3 and biotype 4 resistance was also moderate (45–55%). A total of 1847 SNP markers were mapped to 22 linkage groups, and loci for resistance to both aphid biotypes were mapped to a 14 cM region on chromosome 18 using composite interval mapping. The locus explained between 26 and 40% of the phenotypic variation suggests the presence of a major locus and additional unidentified minor quantitative trait loci (QTL). A new symbol qRag-G is proposed to designate this new locus that will be useful for the development of durable aphid-resistant soybean cultivars.