Designing sustainable strategies to combat cabbage root fly infestation in oil seed rape (Brassica napus)
Winter oilseed rape (Brassica napus; OSR) is an important crop in Germany that is suffering from severe damage by root-feeding larvae of the cabbage root fly, Delia radicum. Despite variation among oilseed rape accessions, sufficiently strong natural resistance to D. radicum has not been identified in the oilseed rape germplasm yet. Our research showed that larvae of D. radicum can detoxify isothiocyanate (ITC), the typical chemical defences of their host plants. By assembling and annotating a high-quality genome of D. radicum and combining genomic and transcriptomic data, we identified genes participating in the ITC detoxification. In addition, we found that the larval gut bacterial community shifts when fed on ITCs. Bacteria known to contain saxA genes enabling ITC breakdown became more prominent in larvae on ITC diets.
In this project, we will validate our basic knowledge to design an integrated strategy to control D. radicum together with NPZi, a German company with expertise in OSR breeding research. The main aim is to design novel approaches for environmental-friendly control of D. radicum in oilseed rape by considering host, herbivore and gut bacterial communities. First, we will screen a panel of oilseed rape accessions and introgression lines to identify metabolites and volatiles related to reduced larval performance and attractiveness to the female flies. The NPZi oilseed rape mutant population will serve to select candidate mutants to verify the chemical factors identified. We will use the D. radicum genome to identify key genes involved in detoxification, which we can specifically target by RNA interference (RNAi) biopesticides. In addition, we will target bacterial detoxification genes to reduce the detoxification capacity of the gut bacterial community. Novel RNAi-based biopesticides will be formulated and tested for their effectivity in the lab the field. By targeting all interaction partners in this tripartite interaction, we enhance the prospect of sustainably controlling Delia damage in oilseed rape.