Comparison of populations of two soybean aphid biotypes on different soybean entries

Soybean, Glycine max (L.) Merr is one of the most important cultivated crops in the world .The soybean aphid, Aphis glycines Matsumura, is a major pest of soybean and was first detected in Wisconsin in 2000. It has spread into most, if not all, soybean producing areas of the United States and Canada since its first report. Host plant resistance to insects is an important alternative to other controls and is more sustainable than any other control methods against this insect. Recent studies identified two soybean aphid biotypes during 2005 in just five years after its invasion. This study includes the entries from Kansas, Michigan and Nebraska soybean germplasms. Also it is the first attempt to study the different Kansas soybean entries response to Ohio biotype. The plants were screened by infested at V1 stage with 6 aphids per plant and populations counted after 7 days. The results showed that the earlier resistant entries to Illinois biotype (K1639, K1642, K1613 K1621, Dowling and Jackson) were susceptible to the new Ohio biotype with large populations developing on these entries. But two of the Michigan entries (EO 6902 and EO 7906-2) showed resistance to both Ohio and Illinois biotypes. Further characterization of resistance made clear that they showed antibiosis type of resistance with the two above biotypes. Thus, it is concluded that we found two entries resistant to both Ohio and Illinois biotypes and the Ohio biotype overcame the several different sources of resistance in previous found resistant entries.