Impact of Combining the Rag1 and Rag2 Alleles for Aphid Resistance on Agronomic and Seed Traits of Soybean

Damage to soybean [Glycine max (L.) Merr.] by the soybean aphid (Aphis glycines Matsumura) has been of economic concern in the midwestern United States since 2000. Soybean lines with both the Rag1 and Rag2 alleles have had substantially reduced aphid development compared to lines with either of the two alleles individually. The objective of our study was to evaluate the impact of the two alleles on agronomic and seed traits of soybean by comparing 22 BC3 F-2:4 lines with the two alleles to their susceptible recurrent parent 'IA3027'. The replicated experiment was grown under aphid-free conditions at three Iowa environments during 2011. Although the mean yield of the backcross (BC) lines was significantly less than IA3027 by 147 g kg(-1) (4.5%), 15 of the 22 BC lines (68%) were not significantly different than the recurrent parent. The mean of the BC lines was significantly different than the recurrent parent for maturity, plant height, lodging, oil concentration, and seed weight, but there were individual BC lines that were not significantly different from the recurrent parent for all of the traits. The results indicated that it should be possible to develop resistant cultivars with the Rag1 and Rag2 alleles that have comparable performance for agronomic and seed traits to those of susceptible cultivars.