Differential resistance of switchgrass Panicum virgatum L. lines to fall armyworms Spodoptera frugiperda (J. E. Smith)

Abstract

Six cultivars of switchgrass Panicum virgatum L., a plant native to North America that has potential as a bioenergy source, were evaluated for resistance to feeding by the fall armyworm Spodoptera frugiperda (J. E. Smith). Although no mortality was noted, seedlings of the cultivar 'Trailblazer' and older plants of the cultivar 'Blackwell' were among the most resistant to feeding by S. frugiperda. Some field-collected samples from natural habitat were fed upon by S. frugiperda as readily as were the cultivars, while others caused high mortality after 2 days. Enzyme assays indicated relative differences in expression of two peroxidases thought to be involved in insect resistance in maize, but not in two chitinolytic enzymes. Genomic searches based on maize-sequence templates for the aforementioned genes identified homologs in switchgrass. Sequencing of cDNA coding for these genes identified some differences, especially in the cationic peroxidase, which could influence relative activity. These results indicate switchgrass germplasm has varying resistance to fall armyworms which could be a function of gene sequence diversity, as well as of variation in gene expression due to differences in ploidy levels or other factors.

Categories of Resistance to Greenbug and Yellow Sugarcane Aphid (Hemiptera: Aphididae) in Three Tetraploid Switchgrass Populations

“…As an example, in the related native warm-season perennial, buffalograss, Buchloë dactyloides (Nuttall) Engelmann, an emergence in multiple important pests was demonstrated with increased use of this species as a turfgrass [4,16]. Likewise, recent work has demonstrated that insect problems may occur, particularly as production increases [1,9,22,28]. In 2004, a poorly understood species, Blastobasis repartella (Dietz), was rediscovered, and appears to be a monophagous stem-borer restricted to switchgrass [1,28].…”

“…Four additional lepidopterans, Spodoptera frugiperda (J.E. Smith) [9,10,24,30], Mythimna unipuncta (Haworth) [29], Papaipema nebris (Guenée), and Haimbachia albescens Capps [31] have also been recently documented on various populations of switchgrass. Burd et al [6] demonstrated that multiple switchgrass populations are suitable hosts to several important cereal aphids including: Schizaphis graminum (Rondani) (greenbug), Rhopalosiphum padi (L.) (bird-cherry oat aphid), Rhopalosiphum maidis (Fitch) (corn leaf aphid), and Sipha flava (Forbes) (yellow sugarcane aphid).…”

“…Further, plant resistance may improve the efficiency of insect biological control agents, synergizing the interactions between the insectresistant plants and natural enemies by decreasing the vigor of the insect pest [34,35]. Dowd and Johnson [9] noted that the apparent lack of insect pest problems in switchgrass suggested that insect resistance genes are present. Differential resistance has been documented among switchgrass populations to potential insect pests including, S. frugiperda [9,10], as well as S. flava and S. graminum [19].…”

“…Dowd and Johnson [9] noted that the apparent lack of insect pest problems in switchgrass suggested that insect resistance genes are present. Differential resistance has been documented among switchgrass populations to potential insect pests including, S. frugiperda [9,10], as well as S. flava and S. graminum [19]. Further, Dowd et al [10] were able show that multiple resistance mechanisms may be at work; however, the categories and relative levels of resistance being expressed among these populations have remained undocumented.…”

Characterization of Greenbug Feeding Behavior and Aphid (Hemiptera: Aphididae) Host Preference in Relation to Resistant and Susceptible Tetraploid Switchgrass Populations

“…Differential resistance to potential insect pests has been demonstrated in various switchgrass populations. Dowd and Johnson [12] found differential resistance among several octaploid switchgrass populations to Spodoptera frugiperda (J. E. Smith), with "Trailblazer" and "Blackwell" being the most resistant. Differential resistance was also demonstrated among four tetraploid switchgrass populations to two key aphid species, S. graminum and S. flava [26,27].…”