Improved high-throughput bioassay for Rhyzopertha dominica (F.) (Coleoptera: Bostrichidae)

Abstract

As we gain more information through functional genomic studies of Rhyzopertha dominica (F.), we need a high-throughput bioassay system to screen potential biopesticides. Rhyzopertha dominica is an internal feeder during immature stages and presents unique challenges with traditional bioassay methods. Our primary goal was to develop a fast method to evaluate larval development on small amounts of material incorporated homogenously in an artificial diet. Herein we describe a new method that incorporates an artificial diet composed of egg yolk, brewer's yeast, and amylopectin for evaluating the effect of potential biopesticides on the development of R. dominica larvae. Evaluation is accomplished through visual inspection of digital X-ray images, or weighing containers of infested larvae on diet treatments. We demonstrate the method with aprotinin and Bacillus thuringiensis Cry3Aa protoxin, test materials that retard the development of R. dominica larvae. Different bioassay containers were evaluated, including a single larva assay with pipette tips or 8-strip tubes, or a group bioassay in black 16-well trays. In addition to improvements in time and manual manipulations, larvae can now be obtained for biochemical studies by gently washing away the diet. Discrimination of the effect of test materials by weighing the infested containers at specific timepoints was the most simplified approach to rapidly screen test compounds.