Survival and Growth of Diabrotica Balteata Larvae on Insect-Resistant Sweetpotato Genotypes

Authors: Jackson, D; Bohac, Janice

Submitted to: Journal of Agricultural and Urban Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/19/2007
Publication Date: 4/5/2006
Citation: Jackson, D.M., Bohac, J. 2006. Survival and Growth of Diabrotica Balteata Larvae on Insect-Resistant Sweetpotato Genotypes. Journal of Agricultural and Urban Entomology. 23:77-86.

Interpretive Summary: Sweetpotatoes are damaged by several insect species, and streamlined procedures are needed for evaluating resistance to these pests in new breeding materials. Thus, a laboratory procedure was developed to evaluate sweetpotato breeding lines against the larvae of the banded cucumber beetle, a major pest of this crop. Small plugs of sweetpotato were placed into plastic tubes to which one young larva was added. These were held at 25C for 12 days and surviving larvae were weighed. Of the five sweetpotato varieties evaluated, larval growth on the peel of the three resistant varieties (Liberty, Regal, and Charleston Scarlet) was significantly lower than for the susceptible cultivars (Beauregard or SC1149 19). Laboratory results were consistent with field observations, indicating that these techniques could be useful for evaluating resistance of sweetpotatoes to cucumber beetle larvae and other insect pests.

Technical Abstract: Production of sweetpotatoes is severely limited by several insect pests, and new pest management approaches for this crop are needed. A host plant resistance research program typically depends on reliable bioassay procedures to streamline evaluation of germplasm. Thus, a laboratory bioassay procedure was developed for larvae of the banded cucumber beetle, Diabrotica balteata LeConte. Small plugs of sweetpotato peel (periderm plus cortex), cortex, or stele were placed into micro centrifuge tubes (1.5 ml) containing 1.0 ml water agar to prevent desiccation. One second instar D. balteata was added to each micro centrifuge tube, and held at 25C for 12 days. Surviving larvae were weighed. The peels and stele of five sweetpotato genotypes were evaluated. Diabrotica larvae grew larger when they were fed stele from any of the sweetpotato genotypes than when they were fed peels of any genotype. Larval growth was not different among genotypes for any of the stele treatments. However, larval growth on the peels of the resistant genotypes (Liberty, Regal, and Charleston Scarlet) was significantly lower than for the susceptible cultivars (Beauregard or SC1149 19). Larvae did not survive well or gain much weight when they were starved or fed only the scraped periderm of Regal. There was no difference in the inhibition of larval growth by the cortex or the peel of Regal roots. These bioassays were consistent with field results, indicating that these techniques could be useful for evaluating pest resistance in sweetpotato genotypes for Diabrotica and other insect species.