Soybean aphid intrabiotype variability based on colonization of specific soybean genotypes

Abstract

The soybean aphid, Aphis glycines Matsumura (Hemiptera: Aphididae), is one of the most destructive insect pests on soybeans in the United States. One method for managing this pest is through host plant resistance. Since its arrival in 2000, 4 aphid biotypes have been identified that are able to overcome soybean aphid resistance (Rag) genes. A soybean aphid isolate collected from Moline, Illinois readily colonized soybean plants with the soybean aphid resistance gene Rag2, unlike biotypes 1 and 2, but similar to soybean aphid biotype 3. Two no-choice experiments compared the virulence of the Moline isolate with biotype 3. In both experiments, differences in aphid population counts were not significant (P > 0.05) on soybean genotypes LD08-12957a (Rag2) and LD11-5413a (Rag2), but the aphid counts for the Moline isolate were significantly (P < 0.05) lower than the aphid counts for the biotype 3 isolate on the soybean genotypes Dowling (Rag1), LD05-16611 (Rag1), LD11-4576a (Rag1), and PI 567598B (rag1b and rag3). The Moline isolate was a variant of aphid biotype 3, which is the first report showing that soybean aphid isolates classified as the same biotype, based on virulence against specific Rag genes, can differ in aggressiveness or ability to colonize specific host genotypes.

Geographic Distribution and Intrabiotypic Variability of Four Soybean Aphid Biotypes

“…We agree with Pawlowski et al (2015), who concluded that any new soybean cultivars should be tested at multiple locations to ensure that they are exposed to as many biotypes as possible. Wenger and Michel (2013) concluded that soybean aphid biotypes were genetically indistinguishable across a large region because of high rates of interpopulation immigration and admixture.…”

“…Their two isolates (Biotype 3) differed in population growth by 3 to 10 times. Thus, in 2013, we observed similar differences across isolates of Biotype 3, as did Pawlowski et al (2015). 6b-6d).…”

“…McCarville et al (2014) observed significant variation in resistance between the Rag1 and Rag2 traits with respect to aphid suppression within five field tests out of their 23 locationyears. Pawlowski et al (2015) studied the intrabiotypic variability of Biotype 3 using a standard isolate and a newer one. Pawlowski et al (2015) studied the intrabiotypic variability of Biotype 3 using a standard isolate and a newer one.…”

“…Biotype 1 is not virulent (i.e., avirulent) to all Rag loci. Pawlowski et al (2015) believe that additional biotypes will likely occur as new Rag loci are discovered and tested. Biotype 3 is virulent to Rag2 while remaining mostly avirulent to Rag1 soybean (Hill et al, 2010).…”

“…Thus, cross resistance is possible. Pawlowski et al (2015) believe that additional biotypes will likely occur as new Rag loci are discovered and tested.…”