University of Nebraska - Lincoln DigitalCommons@University of Nebraska - Lincoln Faculty Publications: Department of Entomology Entomology, Department of 8-2014 Characterization of Greenbug Feeding Behavior and Aphid (Hemiptera: Aphididae) Host Preference in Relation to Resistant and Susceptible Tetraploid Switchgrass Populations Kyle G. Koch University of Nebraska-Lincoln, [email protected] Nathan Palmer USDA-ARS, [email protected] Mitch Stamm University of Nebraska-Lincoln Jeff D. Bradshaw University of Nebraska-Lincoln, [email protected] Erin Blankenship University of Nebraska-Lincoln, [email protected] See next page for additional authors Follow this and additional works at: https://digitalcommons.unl.edu/entomologyfacpub Part of the Entomology Commons Koch, Kyle G.; Palmer, Nathan; Stamm, Mitch; Bradshaw, Jeff D.; Blankenship, Erin; Baird, Lisa M.; Sarath, Gautam; and Heng-Moss, Tiffany M., "Characterization of Greenbug Feeding Behavior and Aphid (Hemiptera: Aphididae) Host Preference in Relation to Resistant and Susceptible Tetraploid Switchgrass Populations" (2014). Faculty Publications: Department of Entomology. 425. https://digitalcommons.unl.edu/entomologyfacpub/425 This Article is brought to you for free and open access by the Entomology, Department of at DigitalCommons@University of Nebraska - Lincoln. It has been accepted for inclusion in Faculty Publications: Department of Entomology by an authorized administrator of DigitalCommons@University of Nebraska - Lincoln. Authors Kyle G. Koch, Nathan Palmer, Mitch Stamm, Jeff D. Bradshaw, Erin Blankenship, Lisa M. Baird, Gautam Sarath, and Tiffany M. Heng-Moss This article is available at DigitalCommons@University of Nebraska - Lincoln: https://digitalcommons.unl.edu/ entomologyfacpub/425 Bioenerg. Res. (2015) 8:165–174 DOI 10.1007/s12155-014-9510-0 Supplemental material follows the references. Characterization of Greenbug Feeding Behavior and Aphid (Hemiptera: Aphididae) Host Preference in Relation to Resistant and Susceptible Tetraploid Switchgrass Populations Kyle G. Koch & Nathan Palmer & Mitch Stamm & Jeff D. Bradshaw & Erin Blankenship & Lisa M. Baird & Gautam Sarath & Tiffany M. Heng-Moss Published online: 1 August 2014 # Springer Science+Business Media New York 2014 Abstract Two choice studies were performed to evaluate on switchgrasses indicated no differences for the time to first greenbug, Schizaphis graminum (Rondani), and yellow sug- probe or time to first sieve element phase among switchgrass arcane aphid, Sipha flava (Forbes), preference for two tetra- populations. However, duration of sieve element phases for ploid switchgrass populations, Summer and Kanlow, and one S. graminum was significantly less on Kanlow compared to experimental hybrid, K×S, derived by crossing Kanlow K×S and Summer. S. graminum also had a significantly lower (male)×Summer (female) plants. Additionally, an assessment potential phloem ingestion index (PPII) and few aphids show- of S. graminum feeding behavior was performed on the same ing sustained phloem ingestion on Kanlow as compared to switchgrass populations, by using the electrical penetration K×S and Summer plants. These results suggest that resistance graph (EPG) technique. Choice studies for S. flava indicated a factors (chemical or mechanical) in Kanlow are located in the lack of antixenosis, with no preference by aphids among any phloem tissue. At the whole leaf level, some differences were of the switchgrass populations at any time point. However, observed for a subset of polar metabolites, although Kanlow choice studies with S. graminum indicated a preference for the plants were significantly enriched for oxalic acid. K×S 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 Keywords Choice studies . EPG . Feeding behavior . Greenbug . Plant resistance . Tetraploid switchgrass . Yellow sugarcane aphid Electronic supplementary material The online version of this article (doi:10.1007/s12155-014-9510-0) contains supplementary material, which is available to authorized users. : : K. G. Koch M. Stamm T. M. Heng-Moss (*) Introduction Department of Entomology, University of Nebraska, 201B Entomology Hall, Lincoln, NE 68583-0816, USA e-mail: [email protected] Switchgrass, Panicum virgatum L., is a widely distributed, : polyploid warm-season perennial grass with excellent poten- N. Palmer G. Sarath tial as a biomass crop [8]. However, long-term sustainability Grain, Forage and Bioenergy Research Unit, USDA-ARS, Lincoln, of switchgrass as a bioenergy feedstock will require efforts NE 68583, USA directed at improved biomass yield under a variety of biotic J. D. Bradshaw and abiotic stress factors. Department of Entomology, Panhandle Research & Extension Insect pests contribute significantly to over US$1 billion Center, University of Nebraska, Scottsbluff, NE 69361, USA crop losses through both direct and indirect injury, and it can E. Blankenship be anticipated that bioenergy crops will be no exception to Department of Statistics, University of Nebraska, Lincoln, insect-related losses in yields. Recently, Koch et al. [26, 27] NE 68583, USA have shown that tetraploid switchgrasses can serve as suitable hosts for two different aphids, namely the greenbug, L. M. Baird Department of Biology, University of San Diego, San Diego, Schizaphis graminum (Rondani), and the yellow sugarcane CA 92110, USA aphid, Sipha flava (Forbes). Both aphids can be found across 166 Bioenerg. Res. (2015) 8:165–174 the USA and have been well characterized as pests of many Antixenosis Studies Choice studies were performed for both cultivated and native grasses [6, 7, 24, 31]. S. graminum and S. flava to assess aphid preference among Aphids are particularly important crop pests and may the three switchgrass populations. Plants were grown in plas- cause plant damage by removing photo assimilates and tic nursery pots (9 cm in diameter by 9 cm in depth) containing transmitting an array of plant viruses [44]. During feed- a Fafard Growing Media (Mix No. 3B) (Conrad Fafard, ing, the stylets of the aphid’s piercing-sucking mouthparts Agawam, MA). One seed of each population of switchgrass penetrate plant tissue to feed on phloem sieve elements (Kanlow, Summer, and K×S) was planted approximately [11, 37, 44, 52]. Penetrations of plant tissues by aphids 2 cm from the perimeter of the pot. Within a pot, seeds for can be monitored by the electrical penetration graph each population were equally spaced from each other and the (EPG) technique [52], and stylet penetrations may provide center of the pot (5.2 cm between grasses and 3 cm from cues about host-plant acceptance or rejection [51, 52]. center) and randomly seeded with relation to each other. A The EPG technique was first described by McLean and total of ten pots were used. Plants were maintained in a Kinsey [30], using an alternating current (AC) recorder greenhouse at 25±7 °C with the lighting augmented by 400- system, and later by Tjallingii [47], using a direct current W metal-halide lamps to produce a photoperiod of 16:8 (L:D) (DC)-based monitor. The EPG technique allows the re- h until the plants reached the V1 developmental stage, as cording of signal waveforms corresponding to different described by Moore et al. [32]. Plants were fertilized every insect activities and the position of the stylet tips within 2 weeks with a water-soluble (20:10:20 N-P-K) fertilizer. the plant tissues [48, 52]. Further, when considered in Prior to introduction, aphids were placed in a petri dish and combination, stylet activities and position may be useful starved for approximately 1 h. Following the pretreatment, 50 in determining the kind of resistance mechanisms that adult apterous aphids were introduced onto filter paper may be involved at the plant tissue level [10, 11, 21, 53]. (1.5 cm in diameter) in the center of the arena. Pots were then Although the EPG technique has been widely used to study arranged within a heavy-duty plastic flat (~50 cm in length by the feeding behavior of several species of aphids on many host 36 cm in width by 7.6 cm in depth) filled with water to prevent plants [53], no studies have documented aphid feeding behav- aphids from moving between pots. The number of aphids was ior on switchgrass. Further, no attempt has been made to visually documented by counting on each switchgrass popu- document the presence of antixenosis within switchgrass pop- lation at 1, 2, 4, 8, 24, 48, and 72 h after aphid introduction. ulations to potential insect pests. Therefore, the specific ob- Experiments were conducted in a controlled laboratory setting jectives of this research were to characterize the expression of at 23±5 °C with continuous light. The experimental design antixenosis among selected switchgrass populations of was a randomized complete block design with 10 replications S. graminum and S. flava and compare S. graminum feeding per experiment. behavior on resistant and susceptible switchgrasses using the Choice studies were analyzed as a repeated measures de- EPG technique. sign using generalized linear mixed model analyses (PROC GLIMMIX) [41] to identify differences in aphid preference for resistant and susceptible switchgrass populations. The corrected Akaike’s information criterion (AICC) fit statistic Materials and Methods was used to determine the most appropriate covariance struc- ture, and the first-order autoregressive [AR (1)] covariance Plant Material Choice