Location: Wheat, Sorghum and Forage ResearchTitle: Characterization of greenbug feeding behavior and aphid (Hemiptera: Aphididae) host preference in relation to resistant and susceptible tetraploid switchgrass populations Author
|Palmer, Nathan - Nate|
Submitted to: BioEnergy Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/11/2014
Publication Date: 8/1/2014
Citation: Koch, K.G., Palmer, N.A., Stamm, M., Heng-Moss, T.M., Bradshaw, J.D., Blankenship, E., Baird, L.M., Sarath, G. 2014. Characterization of greenbug feeding behavior and aphid (Hemiptera: Aphididae) host preference in relation to resistant and susceptible tetraploid switchgrass populations. BioEnergy Research. DOI: 10.1007/s12155-014-9510-0. Interpretive Summary: Previous research has shown that many switchgrasses are prone to herbivory by aphids; however some cultivars are resistant to aphid feeding. The underlying reasons for these observations are not known. Aphids feed on the vascular system of plants by sucking nutrients required for plant growth. These unique feeding strategies can be exploited to understand both aphid feeding behaviors as well as determining the potential causes underlying plant resistance to aphid herbivory. Here, we have used a sophisticated instrument called the Electrical Penetration Graph (EPG) to monitor aphid feeding on a diverse array of switchgrasses. Data show that populations susceptible to aphid herbivory support long-feeding times for aphids, whereas in resistance plants, aphids did not feed as long. Overall results from these various experiments indicate that plant resistance is likely to be based in one part of the plant’s vasculature, called the phloem. The mechanisms involved in phloem-based resistance can now be investigated, and applied to the development of more resistant switchgrasses in the future.
Technical Abstract: Two choice studies were performed to evaluate geenbug, Schizaphis graminum (Rondani), and yellow sugarcane aphid, Sipha flava (Forbes), preference for two tetraploid switchgrass populations, Summer and Kanlow, and one experimental hybrid, KxS, derived by crossing Kanlow (male) x Summer (female) plants. Additionally, an assessment of S. graminum feeding behavior was performed on the same switchgrass populations, by using the electrical penetration graph (EPG) technique. Choice studies for S. flava indicated a lack of antixenosis, with no preference by aphids among any of the switchgrass populations at any time point. However, choice studies with S. graminum indicated a preference for the KxS plants at 24 h after aphid introduction. No obvious differences were observed for the leaf surfaces between the three populations. Feeding behavior studies for S. graminum on switchgrasses indicated no differences for the time to first probe or time to first sieve element phase among switchgrass populations. However, duration of sieve element phases for S. graminum was significantly less on Kanlow compared to KxS and Summer. Schizaphis graminum also had a significantly lower potential phloem ingestion index (PPII) and few aphids showing sustained phloem ingestion on Kanlow as compared to KxS and Summer plants. These results suggest that resistance factors (chemical or mechanical) in Kanlow are located in the phloem tissue. At the whole leaf level, some differences were observed for a subset of polar metabolites, although Kanlow plants were significantly enriched for oxalic acid.