Identification of genetic factors controlling the efficiency of Agrobacterium rhizogenes-mediated transformation in Brassica oleracea by QTL analysis

We have identified quantitative trait loci (QTL) for transgenic and adventitious root production using an Agrobacterium rhizogenes-mediated co-transformation system in conjunction with a Brassica oleracea double haploid (DH) mapping population. Three QTL for green fluorescent protein (GFP)-fluorescent root production and four QTL for adventitious root production were identified as accounting for 26% and 32% of the genetic variation in the population, respectively. Two of the QTL regions identified were common to both transgenic and adventitious root production. Two different methods of QTL analysis were employed (marker regression and interval mapping) and with the exception of one region on linkage group O7 for transgenic root production, both techniques detected the same regions of the genome. The regions we identified to be associated with the control of transgenic root production following A. rhizogenes-mediated transformation are the first to be detected using a QTL mapping approach. In addition, this is the first study to identify genetic regions that co-regulate both transgenic and adventitious root production within the constraints of an A. rhizogenes-mediated transformation process. We have identified plant genotypes that do not produce any transgenic roots that may be deficient for T-DNA integration via illegitimate recombination and that may also be potentially important for the development of homologous recombination protocols. Conversely, we have also identified plant genotypes with high rates of transgenic root production that will be critical in the development of high throughput transformation systems.