Breeding for resistance to root flies (Delia spp.) in cabbage, Brassica oleracea, using genomic approaches
06 / 2011 - unknown
The Cabbage root flies (Delia radicum (L.) and D. floralis (Fallén) (Diptera: Anthomyiidae) constitute the most damaging biotic factors in cabbage (Brassica oleracea L.) production in Western Europe and North America. Economic losses have been estimated to amount up to $ 100 million in some years. The threat to cabbage crops posed by Delia species has recently become acute due to the legislative ban by the European Union of the major chemical insecticide to control cabbage root flies. Within B. oleracea varietal differences in resistance are minor and no effective sources of resistance are known. As genetic modification is not a marketable option in the current setting, in this project the resistance found in related species will be crossed into the B. oleracea genome. High levels of antibiosis have been reported to be available in the uncultivated species B. fruticulosa, B. incana, B. villosa. The chemical nature of the antibiosis type of resistance against the root-feeding maggots of Delia species documented for wild Brassica species has not been addressed at all to date. Recently developed metabolomics approaches have the potential to detect novel compounds to be active in this interaction. In order to make B. oleracea plant material resistant to Delia flies, we propose to study physiology and behavior of Delia ? Brassica interactions, the plant metabolome and global plant gene expression (Part I). In a parallel project, Brassica species hybrids will be produced and F2 / F3 generations will be studied using QTL-, marker-assisted selection and genomic approaches to determine the genetic basis of resistance (Part II). Project Part I aims to: (1) characterise genetic variation within and between Delia spp. populations (2) develop robust greenhouse and field bioassays; (3) quantify antibiosis resistance; (4) characterise physiological and behavioural interactions between rootfly larvae and Brassica spp. roots in mini-rhizotrons; (5) perform metabolic profiling using LC-MS and gene expression analysis using micro-arrays of the ten most susceptible and ten most resistant plants of the F2 (F3) population (6) identification of resistance mechanism(s). Innovative aspects of part II of the project are: (1) introgression of resistance genes from B. fruticulosa into B. oleracea, not been documented before. (2) Mapping of resistance within the donor species B. fruticulosa; (3) integration of QTL-mapping, construction of SNP-maps and exploitaion of synteny within the genus Brassica to identify candidate R-genes.