Challenges and prospects of wild soybean as a resistance source against soybean aphid (Hemiptera: Aphididae)

Authors: Hesler, Louis; TILMON, KELLEY - The Ohio State University; VARENHORST, ADAM - South Dakota State University; CONZEMIUS, SOPHIA - Clemson University; Taliercio, Earl; Beckendorf, Eric

Submitted to: Annals of the Entomological Society of America
Publication Type: Literature Review
Publication Acceptance Date: 8/6/2021
Publication Date: 9/22/2021
Citation: Hesler, L.S., Tilmon, K.J., Varenhorst, A.J., Conzemius, S.R., Taliercio, E.W., Beckendorf, E.A. 2021. Challenges and prospects of wild soybean as a resistance source against soybean aphid (Hemiptera: Aphididae). Annals of the Entomological Society of America. 115:25-38. https://doi.org/10.1093/aesa/saab033.
DOI: https://doi.org/10.1093/aesa/saab033

Interpretive Summary: The soybean aphid has been a longstanding sporadic pest of cultivated soybean in East Asia, it has become a major pest of soybean in the north-central United States and south-central Canada since 2000. Soybean producers have relied heavily on insecticides to manage soybean aphid, but an increasing frequency of insecticide resistant populations in the United States and Canada has turned attention to alternative management tactics such as aphid-resistant cultivars. The development and adoption of aphid-resistant cultivars has been complicated by the discovery of various strains of soybean aphid in North America and China that are able to overcome one or more plant resistance genes. Obtaining a large diversity of resistance genes may aid the development of aphid-resistant soybean cultivars and enhance strategies that ensure their long-term success. However, cultivated soybean has a narrow genetic base, and additional resistance genes may need to be obtained from a wild relative of soybean known as soja. There are various challenges in working with soja such as low seed stocks, a hard seed coat, low viability, and viny growth habit that limit its usability, but workarounds to these challenges have been developed and are discussed in this article. Despite the hurdles in working with soja, numerous soja lines with aphid resistance have been identified. The application of sophisticated genetic techniques has increased the potential for transferring these genes from soja and breeding them into soybean. Resistance from soja accession ‘85-32’ has been genetically characterized with two novel resistance genes, and one of them, Rag6, has been made available in breeding lines adapted to the Midwestern United States. This could enhance its incorporation into future soybean cultivars. The genetic characterization of aphid-resistance in other soja accessions is sorely needed to fully realize their potential for enhancing the durability of aphid-resistant cultivars and improving soybean pest management.

Technical Abstract: The soybean aphid, Aphis glycines Matsumura, has been a longstanding sporadic pest of soybean (Glycine max) in its native range of East Asia. Since 2000, it has been a major pest of soybean in the north-central United States and south-central Canada. Soybean producers have relied heavily on insecticides to manage soybean aphid, but increasing frequency of insecticide resistant populations in four American states and one Canadian province has turned attention to alternative management tactics such as the use of aphid-resistant cultivars. The development and adoption of aphid-resistant cultivars has been complicated by the discovery of multiple virulent biotypes of soybean aphid in North America and China. Obtaining a large repertoire of resistance genes may facilitate the development of aphid-resistant cultivars and strengthen strategies that ensure their durability. Given the relatively narrow genetic base of cultivated soybean, G. soja (soja) and other wild relatives of soybean may be useful sources in building an adequate reservoir of resistance genes. Various logistical challenges in working with soja such as low seed stocks, hardseededness, low viability, and viny growth habit hinder its exploitation, and workarounds for these are discussed. Despite logistical hurdles, numerous soja accessions with aphid resistance have been identified.. The application of genomic and molecular genetic techniques have increased the potential for utilizing soja. Resistance from soja accession ‘85-32’ has been genetically characterized with two novel resistance genes, and one of them, Rag6, has been made available in breeding lines adapted to the Midwestern United States. This could facilitate its incorporation into future soybean cultivars, but genetic characterization of aphid-resistance in other soja accessions is sorely needed to fully realize their potential for enhancing the durability of aphid-resistant cultivars and improving soybean pest management.