The soybean aphid, Aphis glycines Matsumura, was introduced about a decade ago from Asia into North America where it has become a serious pest of soybeans. This invasive pest has rapidly spread throughout the midwestern United States and southern Canada since 2000. We examined 689 individuals obtained from 23 different collections in USA, Korea, China and Japan for testing eight microsatellite loci. To estimate the relative likelihood of alternative introduction scenarios of the soybean aphid, an approximate Bayesian computation (ABC) was performed for microsatellite data as implemented in DIYABC. The ABC analysis tested for three scenarios (B1, B2, and B3) hypothesizing an introduction from one of the Asian countries. In this analysis, scenario B1 obtained the highest posterior probability ranging from 0.90 to 0.91 with a 95% CI of 0.81-0.99 and 0.88-0.94, which assumes an introduction from Korea. The ABC analysis revealed that one hypothetical scenario, which assumes an introduction of the soybean aphid into USA from Korea, was very robustly suggested than the other two scenarios (from China or Japan).

The soybean aphid, Aphis glycines Matsumura, was recently introduced from Asia into North America (NA) where it has become a serious pest of soybeans. This invasive pest has rapidly spread throughout the midwestern United States and southern Canada since 2000. We examined 585 individuals obtained from 23 different collections in USA, Korea, China, and Japan using eight microsatellite loci. Based on analysis of multilocus genotype, gene diversity and number of alleles in NA were averaging 0.40 and 2.70, whereas in Asia averaging 0.55 and 4.32, respectively. The factorial correspondence analysis displayed that some Korean populations were closely related to the NA populations. Structure analysis resulted in two conspicuous clusters, NA and Asia, as the most likelihood number of clusters (K). Bayesian assignment tests revealed that Osan and Milyang populations were most likely assigned to the NA populations. Bottleneck test did not show significance of genetic bottleneck in all populations. We also discuss the invasive history of the soybean aphid in light of population genetics.

Ten novel microsatellite loci were isolated and characterized from the soybean aphid, Aphis glycines. The soybean aphid was recently introduced into North America where it has become a serious pest of soybeans. This invasive pest has rapidly spread throughout the midwestern United States and southern Canada since 2000. The isolated loci were polymorphic, with two to 18 alleles in 20 individuals from a single population in Korea. The analyses revealed that 19 individuals had different multilocus genotypes, showing expected heterozygosity values ranging from 0.180 to 0.891. We report the development of microsatellite markers for A. glycines potentially suitable for further studies of population structure, dispersal, and host alternation.

The soybean aphid, Aphis glycines Matsumura 1917, is well known as a soybean pest in the world. Recently, it has been introduced to North America causing serious damage in U.S. As a cooperative research with USDA-ARS, we have investigated A. glycines in soybean fields, and also examined the colonies on the overwintering host Rhamnus davurica in order to find its natural enemies. It was generally reported that A. glycines has host alternation between the soybean, Glycine max (summer host) and the Dahurian buckthorn, Rhamnus davurica (winter host) in East Asia. However, it was very difficult to identify the soybean aphid, A. glycines, from R. davurica due to the co-existance of at least three Aphis species and the seasonal polymorphisms of each species (e.g, gynopara, ovipara, and male). For species identification, we tested 3 molecular markers, mitochondrial COI, COII, and nuclear EF1α, for 14 collected samples (7 samples from G. max and 7 samples from R. davurica). As a result, we found two different species, A. gossypii and other Aphis sp., are mixed together with A. glycines on R. davurica. We report the biology of A. glycines in Korea, and present species identification using molecular phylogenetic approach.