Antibiosis resistance against larval cabbage root fly, Delia radicum, in wild Brassica-species

Cabbage root flies (Delia radicum) are a major threat to cabbage production in Western Europe and North America. Host plant resistance is the most promising option in controlling cabbage root fly damage. In a no-choice field test, we evaluated 94 accessions belonging to 16 Brassica-species for antibiosis resistance against the larvae. Thirteen accessions were selected as putatively resistant, which were subsequently re-tested in the greenhouse. The proportion of eclosed flies was introduced as the main parameter to assess antibiosis in the greenhouse, together with other insect and plant parameters. High levels of antibiosis resistance were identified in B. fruticulosa PI663081 and B. spinescens BRA2994, with significantly lower proportions of eclosed flies (1 % of the number of eggs used for infestation) compared to other accessions. Both species are difficult to cross with B. oleracea. Plants with a high level of antibiosis and medium to high tolerance were found in several accessions of other Brassica species (B. villosa BRA2922, B. montana BRA2950, B. hilarionis HRIGU12483, B. macrocarpa BRA2944) which are more amenable for crossing with B. oleracea. Selection of the most resistant plants belonging to these accessions may yield promising candidates for breeding cabbages resistant to Delia radicum.