QTLs controlling the production of transgenic and adventitious roots in Brassica oleracea following treatment with Agrobacterium rhizogenes

Brassica oleracea can be genetically engineered using Agrobacterium rhizogenes. The initial stage of this process is the production of transgenic ('hairy') roots; shoots are subsequently regenerated from these roots. Previous work using gus and gfp reporter genes has shown that genotypes of B. oleracea vary in their performance for transgenic root production. Quantitative trait loci (QTLs) controlling this trait have been located in one mapping population. The current study provides evidence that performance for transgenic root production is associated with performance for adventitious (non-transgenic) root production in B. oleracea across a second mapping population. This is shown by regression analyses between performance for the two traits and the demonstration that QTLs controlling the two traits map to the same positions within the genome. Since the rate of adventitious root production does not differ significantly in the presence and absence of A. rhizogenes, there is no evidence that the expression of Agrobacterium genes induces adventitious root production. It is apparent that genotypes exhibiting high adventitious root production in the absence of A. rhizogenes will also tend to show high transgenic root production, thereby allowing the selection of lines that are more efficiently transformed.