Submitted to: Theoretical and Applied Genetics
Publication Type: Peer reviewed journal
Publication Acceptance Date: 9/17/2013
Publication Date: 9/27/2013
Publication URL: http://handle.nal.usda.gov/10113/60188
Citation: Bonin, C.M., Kim, K., Cregan, P.B., Hill, C.B., Hartman, G.L., Diers, B.W. 2013. Inheritance of soybean aphid resistance in 21 soybean plant introductions. Theoretical and Applied Genetics. 127(1):43-50. Interpretive Summary: The soybean aphid is a destructive pest of soybean that was first seen in the northern U.S. soybean production areas, as well as in Canada, in 2000. Insecticides are used for soybean aphid control but aphid resistant soybean varieties provide an excellent method to reduce or eliminate aphid infestation and damage with less detrimental environmental impact. Four aphid resistance genes have been defined to date but the ability of the aphid population to evolve new genetic types that can successfully attack previously resistant varieties requires the discovery and deployment of new resistance genes. Thus, the objective of this study was to analyze the progeny from crosses of an aphid susceptible variety with 21 soybean Plant Introduction (PI) accessions identified as carrying resistance to the soybean aphid. The resulting populations were screened for aphid resistance and with genetic markers to determine the position(s) along the soybean chromosomes where the aphid resistance gene(s) were located. These evaluations indicated that soybean aphid resistance appeared to be controlled by a single gene in 14 accessions and two genes in two accessions. In five accessions, the inheritance of resistance was unclear. The positions of the resistance genes in the 21 PI accessions were generally in chromosome regions that were similar to the regions in which the four previously defined resistance genes reside. Further research is now needed to determine if these newly discovered resistance genes offer resistance to aphid biotypes that can attack soybeans that carry the four resistance genes that are currently being used by soybean breeders. This information is of potential use to soybean breeders and geneticists interested in the development of new aphid resistant soybean varieties.
Technical Abstract: The soybean aphid [Aphis glycines Matsumura (Hemiptera: Aphididae)] is one of the most important insect pests on soybean [Glycine max (L.) Merr] in the northern USA and southern Canada, and four resistance loci (Rag1 to 4) have been discovered since the pest was identified in the USA in 2000. The objective of this research was to determine whether resistance expression in recently identified aphid resistant plant introductions (PIs) was associated with the four Rag loci using a collection of 21 F2 populations. The F2 populations were phenotyped with soybean aphid Biotype 1, that is avirulent on plants with any known Rag genes, using choice tests in the greenhouse and tested with genetic markers linked to the four Rag loci. The results of the evaluations indicated that soybean aphid resistance appeared to be controlled by a single dominant gene in 14 PI accessions, by two genes in two PIs, and five PIs had no clear Mendelian segregation ratios. Genetic markers near Rag2 were significantly associated with aphid resistance in 20 PI accessions, the Rag1 region was significantly identified in three PIs, and the Rag3 region was identified in one PI. These results show that single dominant genes were commonly associated with aphid resistance and the majority of these were found in the Rag2 region.