Flooding in Soybeans Induces Differential Transcriptional Responses Between Resistant and Susceptible Soybean Aphids (Aphis glycines)

Many plants possess defensive traits that enable them to naturally tolerate and/or deter insect herbivory (host plant resistance; HPR). Selecting for HPR traits can significantly enhance crop productivity by providing effective and sustainable insect pest management. Some insects have adapted to overcome these defenses (i.e. virulence), threatening the effectiveness, durability, and long-term adoption of HPR crops. Abiotic stressors associated with global climate change may modulate interactions between virulent and avirulent insects and their host plants. In some systems, abiotic stress reduces HPR efficacy and increase plant susceptibility to herbivory. Long-term, this could also favor insect adaptions to overcome HPR (i.e. virulence), although these evolutionary consequences have not been closely examined. To address this knowledge gap, we tested how one abiotic stressor, flooding, affects interactions between soybeans and the invasive, pestiferous soybean aphid (Aphis glycines). We used a full-factorial design with three experiment factors (8 treatment combinations): soybean aphid biotype (avirulent or virulent), soybean variety (susceptible or aphid-resistant), and host plant water stress (flooded or control). Each treatment combination had three biological replicates. Soybean aphid nymphs (<48 hours old) were allowed to feed for 12 hours, at which point they were removed and RNA sequencing analysis was performed to compare changes in aphid gene expression under different host plant stress combinations.