Geographic Distribution of Soybean Aphid Biotypes in the United States and Canada during 2008–2010

Abstract

Soybean aphid (Aphis glycines Matsumura) is a native pest of soybean [Glycine max (L.) Merr.] in eastern Asia and was detected on soybeans in North America in 2000. In 2004, the soybean cultivar Dowling was described to be resistant to soybean aphids with the Rag1 gene for resistance. In 2006, a virulent biotype of soybean aphid in Ohio was reported to proliferate on soybeans with the Rag1 gene. The objective was to survey the occurrence of virulent aphid populations on soybean indicator lines across geographies and years. Nine soybean lines were identified on the basis of their degree of aphid resistance and their importance in breeding programs. Naturally occurring soybean aphid populations were collected in 10 states (Kansas, Illinois, Indiana, Iowa, Michigan, Minnesota, North Dakota, Ohio, South Dakota, and Wisconsin) and the Canadian province of Ontario. The reproductive capacity of field‐collected soybean aphid populations was tested on soybean lines; growth rates were compared in no‐choice field cages at each geographic region across 3 yr. The occurrence of soybean aphid biotypes was highly variable from year to year and across environments. The frequency of Biotypes 2, 3, and 4 was 54, 18, and 7%, respectively, from the 28 soybean aphid populations collected across 3 yr and 11 environments. Plant introduction (PI) 567598B, a natural gene pyramid of rag1c and rag4, had lowest frequency of soybean aphid colonization (18%). Several factors may have contributed to the variability, including genetic diversity of soybean aphids, parthenogenicity, abundance of the overwintering host buckthorn (Rhamnus spp.), and migratory patterns of soybean aphids across the landscape.

Geographic Distribution and Intrabiotypic Variability of Four Soybean Aphid Biotypes

“…For Biotype 2, the value from Cooper et al (2015) is >10 SE higher than the mean observed in this study. For Biotype 2, the value from Cooper et al (2015) is >10 SE higher than the mean observed in this study.…”

“…We determined that two isolates collected in 2013 consisted of two biotypes. Ranges for asymptotic SEs were 0.06 to 0.09 (Biotype 1), 0.04 to 0.05 (Biotype 2), 0.06 to 0.09 (Biotype 3), and 0.03 to 0.06 (Biotype 4) across the 3 yr. Cooper et al (2015) reported frequencies of 0.21, 0.54, 0.18, and 0.07 from samples taken in similar state geographic areas in 2008 through 2010. A c 2 test (8.0, Pr < 0.24, df = 6) and Fisher's exact test (Pr < 0.26, table P < 0.0001,) performed on Table 1 both showed that the probability of the frequency distributions across the four biotypes being the same for all 3 yr is high.…”

“…Orantes et al (2012) and Wenger and Michel (2013) concluded that late-season aphid dispersal homogenizes the aphid population and increases genetic diversity before colonization of buckthorn, the primary host. Cooper et al (2015) were the first to survey the United States and Canada for soybean aphid biotypes. They concluded that individual populations or yearly environmental conditions drive fluctuations in heterozygosity via clonal amplification, rather than specific geographic or biotypic effects.…”

“…Wenger and Michel (2013) found no decrease in multilocus-genotype diversity within Biotype 2 aphids vs. Biotype 1, suggesting that virulent aphid clones share a diverse sexual gene pool. The occurrence of biotypes was highly variable from year to year and across locations, with the greatest virulence variability in Wisconsin (Cooper et al, 2015). Wenger and Michel (2013) believed that such dynamics are to be expected in an asexually reproducing and highly mobile species.…”

“…Wenger and Michel (2013) believed that such dynamics are to be expected in an asexually reproducing and highly mobile species. Cooper et al (2015) calculated the frequency of Biotypes 2, 3, and 4 as 54, 18, and 7%, respectively. They sampled 11 locations from 2008 to 2010 to obtain a total of 28 populations.…”