Sorghum cuticular waxes influence host plant selection by aphids

Authors: CARDONA, JUAN - University Of Nebraska; GROVER, SAJJAN - University Of Nebraska; BUSTA, LUCAS - University Of Minnesota; Sattler, Scott; LOUIS, JOE - University Of Nebraska

Submitted to: Planta
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/18/2022
Publication Date: 12/20/2022
Citation: Cardona, J.B., Grover, S., Busta, L., Sattler, S.E., Louis, J. 2022. Sorghum cuticular waxes influence host plant selection by aphids. Planta. 257:22. https://doi.org/10.1007/s00425-022-04046-3.
DOI: https://doi.org/10.1007/s00425-022-04046-3

Interpretive Summary: Aphids feed on plant sap and can wreak significant economic damage to crops. The sugarcane aphid (SCA) is an emergent pest of sorghum across wide swaths of the US. Plants have a waxy coating on their leaves and stems, and the characteristics of this waxy layer can differentially influence aphid settling and feeding. Sorghum plants are referred to as bloomless when this waxy coating is nearly absent from leaves and stems. In this study, sugarcane aphid behavior was monitor on young normal sorghum plants and bloomless ones. There was no difference in aphid reproduction on either type of plant. However, the aphids preferred to settle on the bloomless plants over the normal ones when given a choice. Overall, these findings suggest that waxes on young sorghum leaves play a critical role in influencing sugarcane aphids. Thus, increasing or altering this waxy coating on leaves and stems through genetic tools may represent new ways to strengthen plant resistance to this damaging pest without insecticides.

Technical Abstract: Cuticular waxes constitute the first point of contact between plants and their environment, and it also protect plants from external stresses. However, the role of waxes in Sorghum bicolor (sorghum) against sugarcane aphid (Melanaphis sacchari), a relatively new and devastating pest of sorghum in the U.S., is not fully understood. In this study, we monitored sugarcane aphid behavior on two genotypes of young sorghum plants with different wax chemistry: a wild-type plant (bloom) with lower C32 alcohol cuticular wax, and a mutant plant (bloomless) with nearly double the amount of wax compared to wild-type plants. No-choice aphid bioassays revealed that sugarcane aphid reproduction did not vary between wild-type and the bloomless plants. Electrical Penetration Graph (EPG) monitoring indicated that the sugarcane aphids spent comparable amount of time feeding from the sieve elements of the wild-type and bloomless plants. However, aphids spent more time feeding on the xylem sap of the bloomless plants compared to the wild-type plants. Furthermore, aphid choice assays revealed that the sugarcane aphids preferred to settle on bloomless compared to wild-type plants. Overall, our results suggest that cuticular waxes on young sorghum leaves play a critical role in influencing host plant selection by sugarcane aphids.