Effect of soybean variety and systemic induction on herbivore feeding guilds

Abstract

Plants are attacked by a variety of herbivores and respond with localized or systemic defenses. Plant defense against one feeding guild (e.g. chewing, piercing/sucking) may also affect alternate feeding guilds. To optimize host plant resistance, interactions between feeding guilds must be understood. Aphids are plant virus vectors whose vector efficiency can be altered by plant defenses. To determine if systemic induction influences aphid feeding behaviors related to virus transmission, three soybean varieties, Davis, Lyon, and Progeny 4906RR, were induced by subjecting plants to soybean looper (SBL) herbivory, or exogenous applications of either jasmonic acid (JA) or salicylic acid (SA). Green peach aphid (GPA) apterae feeding behavior was recorded on induced and control plants using the Electrical Penetration Graph (EPG) technique. SBL growth bioassays were used to assess systemic induction. Previous SBL herbivory reduced SBL larval weights when fed Progeny 4906RR. JA reduced larval weights on Progeny 4906RR and Davis. SA increased SBL larval weights on Lyon. SBL herbivory decreased behaviors associated with nonpersistent virus transmission in Davis and Progeny 4906RR. JA altered behaviors associated with virus transmission in Davis and increased behaviors associated with virus acquisition in Progeny 4906RR. SA delayed probing in Davis, but increased behaviors associated with virus transmission in Progeny 4906RR and Lyon. Inducing host plant resistance with JA may reduce herbivore performance and increase nonpersistent virus transmission. Previous chewing herbivory may decrease nonpersistent virus transmission by aphids but is variety dependent.