bulk grain handlers.

Phosphine is the main fumigant used in Australia to control insect pests in grain storages; both bulk grain handlers and farmers rely on phosphine for the control of insects and more than 80% of grain is fumigated with phosphine during storage.

However, insect resistance to phosphine is increasing in most grain growing areas. To manage this resistance, a rapid and sensitive method for identifying phosphine resistance is required. The current detection method for phosphine resistance relies on time-consuming laboratory bioassay procedures (more than seven days required). A previous study (Park et al., 2008*) had suggested that certain proteins, displayed by two-dimensional electrophoresis (2D-PAGE), from whole Rhyzopertha dominica, differed between resistant and susceptible insects and might be developed as a rapid diagnostic tool.

Research outcomes

This project initially aimed to identify the genes encoding those differing proteins as a first step towards developing a diagnostic tool. However, when the project team used a larger number of strains of R. dominica and a more robust method the results of the previous study were not supported. The project team then proposed that this approach to biomarker discovery might yet be successful if they were to concentrate a more appropriate subset of proteins for proteomic analysis.

Various lines of evidence suggested that mitochondria are a site of important differences associated with phosphine resistance. A proteomic comparison of mitochondrial proteins from susceptible and resistant Tribolium castaneum (chosen for its completed genome sequence) was therefore conducted. The study did not reveal any significant differences in the expression of the more abundant mitochondrial proteins between resistant and susceptible insects. The aim of identifying differentially expressed proteins that are diagnostic for phosphine resistance has been shown to be beyond the scope of this project.

Research Implications

No changes to the use of phosphine for fumigation nor the management of resistance can be recommended as a result of this work.

Acknowledgements

David Schlipalius and Pat Collins (Queensland Primary Industries and Fisheries) supplied some of the insect strains.

*Park, B.-S., Lee, B.-H., Kim, T.-W., Ren, Y.L., Lee, S.-E., 2008. Proteomic evaluation of adults of Rhyzopertha dominica resistant to phosphine. Environmental Toxicology and Pharmacology 25, 121–126.