A New Soybean Aphid (Hemiptera: Aphididae) Biotype Identified

Abstract

Shortly after its arrival, the soybean aphid, Aphis glycines Matsumura (Hemiptera: Aphididae), became established as the most important insect pest of soybean, Glycine max L. (Merr.), in the northern part of the North American soybean production region. Soybean resistance is an environmentally sustainable method to manage the pest and new soybean aphid resistant cultivars are beginning to be deployed into production. However, an earlier study identifying a soybean aphid biotype that could colonize plants with the Rag1 resistance gene has raised concerns about the durability of soybean aphid resistance genes. Choice and nonchoice tests conducted in this study characterized the colonization of a soybean aphid isolate, collected from the overwintering host Frangula alnus P. Mill in Springfield Fen, IN, on different aphid resistant soybean genotypes. This isolate readily colonized plants with the Rag2 resistance gene, distinguishing it from the two biotypes previously characterized and indicating that it represented a new biotype named biotype 3. The identification of soybean aphid biotypes that can overcome Rag1 and Rag2 resistance, even before soybean cultivars with the resistance genes have been deployed in production, suggests that there is high variability in virulence within soybean aphid populations present in North America. Such variability in virulence gives the pest a high potential to adapt to and reduce the effective life of resistance genes deployed in production. The search for new soybean aphid resistance genes must, therefore, continue, along with the development of alternative sustainable strategies to manage the pest.

Evolution of Soybean Aphid Biotypes: Understanding and Managing Virulence to Host-Plant Resistance

“…This biotype was initially collected in 2007 overwintering on Frangula alnus in Indiana. Testing of biotype-3 on both Rag1 and Rag2 varieties revealed that while Rag1 resistance was retained, there was no significant difference no significant difference in colonization, survivability and reproduction with biotype-3 on Rag2 when compared to susceptible varieties (Hill et al 2010). Thus, biotype-3 is defined as avirulent to Rag1 but virulent to Rag2.…”

“…It quickly became invasive and led to an invasion meltdown involving 10 other Eurasian plant, animal and pathogen species (Hiempel et al 2010). In North America, overwintering of the soybean aphid mainly occurs on Rhamnus cathartica (common buckthorn, Figure 3), but can also occur on R. alnifolia (alderleaf buckthorn), R. lanceolata (lanceleaf buckthorn) and F. alnus (glossy buckthorn) Yoo et al 2005;Hill et al 2010). Across its native Asian range, R. davurica and R. japonica are the main hosts .…”

“…Table 1. Known soybean aphid biotypes and virulence relationships (Hill et al 2010) Given the presence of soybean aphid biotypes, questions have arisen on the sustainability and efficacy of incorporating host-plant resistance for soybean aphid management. The evolution of soybean aphid biotypes, and therefore the usefulness of host-plant resistance, depends on 1) the genetic variation for virulence, and 2) how this variation can spread locally, regionally and globally.…”

“…As the discovery of soybean aphid biotypes occurred relatively recently, Hill et al 2010), much information is still needed to determine their influence on resistant soybean varieties. Most critical are determining the relative frequencies and distributions of biotypes, and further elucidating the role of the overwintering host in regards to population genetic issues.…”

“…As an alternative to chemical insecticides, host-plant resistance is a common method of aphid control (Van Emden, 2007), which uses plant hosts with genetically inherited traits that enable the plant to withstand pest attack better than a plant lacking these traits (Smith, 2005). Although soybean aphid resistant varieties have been studied in China (Wu et al, 2004), new soybean varieties have been developed with resistance to the soybean aphid specifically for use in North America (Hill et al, , 2006aMian et al, 2008;Zhang et al, 2009;Hill et al, 2010). Varieties for North American commercial use were available for the first time in 2010.…”