Identification of high levels of resistance to cabbage root fly, Delia radicum, in wild Brassica species

Abstract

Wild Brassica species and associated breeding lines were evaluated for their resistance to Delia radicum, the cabbage root fly, in the field in 1993 and in the field, glasshouse and laboratory in 1996. High levels of antibiosis resistance were discovered in the field in 1993 in Brassica fruticulosa, B. incana, B. villosa and B. spinescens and confirmed in the field in 1996 while two B. oleracea accessions and the susceptible control Brussels sprouts variety, ‘Oliver’, were highly susceptible. No D. radicum pupae were found in the soil around the roots of B. fruticulosa and B. spinescens at the end of the season. All the Brassica species were attractive to egg-laying by D. radicum in the field and in a laboratory experiment and therefore lacked antixenosis resistance. In a series of glasshouse experiments, Brassica species and breeding lines were inoculated with D. radicum eggs supplied from a laboratory culture and the effects of larval feeding on plants recorded. Brassica incana, B. fruticulosa and B. spinescens were highly resistant, most plants surviving, whilst B. macrocarpa and B. villosa were moderately resistant as were two F1 lines bred from a cross between B. macrocarpa and B. oleracea.