Submitted to: Genetic Resources and Crop Evolution
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/7/2009
Publication Date: 4/8/2009
Citation: Dowd, P.F., Johnson, E.T. 2009. Differential resistance of switchgrass Panicum virgatum L. lines to fall armyworms Spodoptera frugiperda (J. E. Smith). Genetic Resources and Crop Evolution. 56:1077-1089. DOI: 10.1007/s10722-009-9430-6
Interpretive Summary: Insects cause major damage to maize and other grass family crops, and promote the spread of toxin-producing molds (a billion dollar problem in the U.S. alone). Switchgrass has the potential to be a significant bioenergy crop in the U.S., but little is known about potential insect pests. Although significant damage occurred compared to “wild” lines tested, named cultivars of switchgrass did have significant differences in feeding damage by fall armyworms. Differences in expression and sequence of genes likely to be involved in insect resistance were also noted for these lines. Once the most effective resistance genes are confirmed through expression studies, they can be monitored during breeding or introduced through transgenic means, including to maize or other crops. Effective insect resistance genes can result in lower cost production, better quality, and safer materials that are subject to mold toxin problems.
Technical Abstract: Six cultivars of switchgrass Panicum virgatum were evaluated for resistance to feeding by the fall armyworm Spodoptera frugiperda. Although no mortality was noted, the cultivar Trailblazer was among the most resistant to feeding by S. frugiperda as seedlings and Blackwell as older plants. Some field collected "wild" lines were fed upon by S. frugiperda as readily as the cultivars while others caused high mortality after two days. Enzyme assays indicated some relative differences in expression of two peroxidases thought to be involved in insect resistance in maize, but not two chitinolytic enzymes. Genomic searches using maize sequence templates for the aforementioned genes identified homologs in switchgrass. Sequencing of RNA coding for these genes identified some differences in sequence, especially in the cationic peroxidase, which could influence relative activity. These results indicate switchgrass has varying resistance to fall armyworms, which could be a function of differences in expression of insect resistance proteins.