Agronomic and seed traits of soybean lines with the Rag1 gene for aphid resistance

Soybean [Glycine max (L.) Merrill] yields can be reduced significantly by infestations of the soybean aphid (Aphis glycines Matsumura). A dominant allele, Rag1, providing resistance to the aphid was identified in PI 548663. The objective of this study was to compare the agronomic and seed traits of 27 BC2F2-derived lines with the Rag1 allele to those of 27 lines with the rag1 allele from the same segregating population. The lines were evaluated under aphid-infested conditions at two Iowa environments in 2008 and under aphid-infested and aphid-free conditions at three Iowa environments during 2009. There were significant differences in mean yield between the Rag1 and rag1 lines in all the aphid-infested environments. The difference in yield between the two types reached 47.6% at one environment under heavy infestation. Under aphid-free conditions, there was no significant difference in mean yield between the two types. The differences between the two types of lines for maturity, height, lodging, protein concentration, oil concentration, and seed weight were either not significant or sufficiently small to make it possible to develop aphid-resistant cultivars with the Rag1 gene that were comparable to susceptible cultivars.