The Resistant Soybean-Aphis glycines Interaction: Current Knowledge and Prospects

Martha I Natukunda,Gustavo C Macintosh

doi:10.3389/fpls.2020.01223

Abstract

Soybean aphids (Aphis glycines Matsumura) are invasive insect pests of soybean, and they cause significant yield losses. Resistance to soybean aphids is conferred by Resistance to Aphis glycines (Rag) genes. Since the first discovery of aphid-resistant soybean genotypes in 2004, several studies have attempted to characterize Rag genes from aphid-resistant soybean genotypes. To date, 12 Rag genes and four quantitative trait loci for aphid resistance have been reported on soybean chromosomes 07, 08, 13, 16, and 17. Although candidate genes have been proposed for several discovered Rag loci, additional studies are needed to pinpoint, validate, and further explain the potential mechanisms of Rag gene action. A major challenge to utilizing host plant resistance is the discovery of virulent aphid biotypes that can colonize aphid-resistant soybean. This occurrence suggests the need for additional studies to devise strategies to enhance the effectiveness of aphid-resistant soybean. In this mini review, we discuss current knowledge on the resistant soybean-Aphis glycines interaction, potential mechanisms of Rag gene action, opportunities to discover new Rag genes, and prospects for utilization of host plant resistance to manage soybean aphids. A clearer understanding of host plant resistance to soybean aphids will guide researchers on strategies for developing soybean varieties with more durable aphid resistance, reducing the present challenge of virulent aphid biotypes.

Highlights

Soybean aphids (Aphis glycines Matsumura) are important insect pests that can cause yield loss of up to 50% in soybean (Glycine max [L.] Merr.) by sucking plant assimilates using their piercing and sucking mouthparts (Ragsdale et al, 2007; Beckendorf et al, 2008; Ragsdale et al, 2011; Tilmon et al, 2011; Bhusal et al, 2013)
Since 2015, pyrethroid-resistant soybean aphids have been reported in Midwestern states (Iowa, Minnesota, North Dakota and South Dakota) (Koch et al, 2016; Koch et al, 2018), which indicates an urgent need for incorporation of host-based resistance in management strategies
Host plant resistance is an environmentally-friendly alternative strategy for the management of soybean aphids compared to application of insecticides

Summary

INTRODUCTION

Soybean aphids (Aphis glycines Matsumura) are important insect pests that can cause yield loss of up to 50% in soybean (Glycine max [L.] Merr.) by sucking plant assimilates using their piercing and sucking mouthparts (stylets) (Ragsdale et al, 2007; Beckendorf et al, 2008; Ragsdale et al, 2011; Tilmon et al, 2011; Bhusal et al, 2013). The type of soybean aphid resistance can be antibiosis (adverse effect on insect biology) or antixenosis (feeding deterrence), and plants exhibiting tolerance (similar yield in the presence or absence of soybean aphids) have been identified (Painter, 1951; Kogan and Ortman, 1978; Hill et al, 2004; Smith, 2005). Application of insecticides such as pyrethroids and organophosphates, has been used to manage soybean aphids to prevent aphid populations from reaching economic injury levels (Koch et al, 2016). This review will not discuss the genomic locations of known Rag loci or QTLs since these aspects have been extensively reviewed by Neupane et al (2019a)

POTENTIAL MECHANISMS OF RAG GENE ACTION

OPPORTUNITIES TO DISCOVER NEW APHID RESISTANCE GENES

Minor SNP allele position