Natural Resistance to and Attraction of the Cabbage Root Fly (Delia radicum) in Oilseed Rape Accessions

Winter oilseed rape (OSR, Brassica napus) is an important crop and frequently attacked by the cabbage root fly larvae (Delia radicum). They damage the taproot, cause plant death, and negatively impact yield. Options to control D. radicum with synthetic pesticides are limited, and no tolerance in OSR has been described. We aim to identify natural resistance in OSR accessions to D. radicum as a starting point for plant breeding. We tested OSR accessions for differences in larval feeding damage, larval performance, female attraction, and oviposition preference. Using a subset of the most and least resistant accessions, we analyzed volatile profiles and leaf traits and assessed root metabolic fingerprints. Resistance to larval damage was related to lower aliphatic glucosinolates and higher lignin-related compound levels. Oviposition preference was linked to higher trichome density. Our results suggest breeding efforts should focus on increasing lignin and decreasing specific glucosinolates in OSR roots.