Interactions between sudangrass lines selected for differing nitrate expression and sorghum aphid

Authors: HAYASHIDA, RAFAEL - Oklahoma State University; CAREY, CAMILLE - Texas A&M University; Springer, Timothy; Knighten, Bailey; Armstrong, John; HOBACK, WYATT - Oklahoma State University

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/23/2024
Publication Date: 9/29/2024
Citation: Hayashida, R., Carey, C., Springer, T.L., Knighten, B.A., Armstrong, J.S., Hoback, W. 2024. Interactions between Sudangrass lines selected for differing nitrate expression and sorghum aphid. Agronomy Journal. 14(10). Article 2250. https://doi.org/10.3390/agronomy14102250.
DOI: https://doi.org/10.3390/agronomy14102250

Interpretive Summary: Sudangrass is widely cultivated as a summer annual forage across the southern Great Plains because of heat tolerance and robust forage yield potential. However, nitrate accumulation and potential to harm livestock have limited the adoption of this forage crop for ruminant feeding. Additionally, the sorghum aphid has been damaging sorghum and Sudangrass production in North America. The SA causes injury to sorghum by extracting sap from plants and altering the plant’s physiology, resulting in a direct reduction in yield. We evaluated the effect of SA feeding on different Sudangrass lines, comparing them to a susceptible and a resistant sorghum variety and measuring physiological responses and nitrate concentration. Additionally, we evaluated these grass lines on SA demographics. Initial infestations of 100 SA per plant that were allowed to feed and proliferate for 20 days significantly increased nitrate concentrations by more than 60% compared to controls. Additionally, the Sudangrass lines selected for high nitrate levels drastically reduced SA demographic parameters, comparable to those of the resistant sorghum control. Although the adoption of resistant cultivars of sorghum and Sudangrass is recommended for aphid management, the Sudangrass lines selected may not be the best option for SA management, because of their accumulation of nitrates that can cause ruminant poisoning.

Technical Abstract: Sudangrass (Sorghum sudanense Stapf) is widely cultivated as a summer annual forage across the southern Great Plains because of heat tolerance and robust forage yield potential. However, nitrate accumulation and potential to harm livestock have limited the adoption of this forage crop for ruminant feeding. Additionally, since 2013, the sorghum aphid (SA), Melanaphis sorghi (Theobald) (Hemiptera: Aphididae), has been damaging sorghum and Sudangrass production in North America. The SA causes injury to sorghum by extracting sap from plants and altering the plant’s physiology, resulting in a direct reduction in yield. The interaction between SA feeding and nitrate accumulation in Sudangrass, has not been determined. In this study, we evaluated the effect of SA feeding on different Sudangrass lines, comparing them to a susceptible and a resistant sorghum variety and measuring physiological responses and nitrate concentration. Additionally, we evaluated these grass lines on SA demographics. Initial infestations of 100 SA per plant that were allowed to feed and proliferate for 20 days significantly increased nitrate concentrations by more than 60% compared to controls. Additionally, the Sudangrass lines selected for high nitrate levels drastically reduced SA demographic parameters, comparable to those of the resistant sorghum control. Although the adoption of resistant cultivars of sorghum and Sudangrass is recommended for aphid management, the Sudangrass lines selected may not be the best option for SA management, because of their accumulation of nitrates that can cause ruminant poisoning.