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

Abstract

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.

Identification and characterization of QTL controlling Agrobacterium‐mediated transient and stable transformation of Brassica oleracea

“…In a previous study (Cogan et al ., 2002) we reported the identification of three QTL controlling the efficiency of Agrobacterium rhizogenes ‐mediated transgenic and adventitious root production using a mapping population derived from a cross between the parents A12DHd and GDDH33. A total of 15 Substitution Lines, containing regions of GDDH33 DNA putatively carrying the target QTL introgressed into the A12DHd genetic background, were selected and their map positions are shown in Figure 1.…”

“…Quantitative Trait Loci (QTL) analysis using a doubled haploid (DH) population and following the insertion of the gfp (green fluorescent protein) transgene revealed three QTL for transgenic root production located on linkage groups O1, O3 and O7. These accounted for 26% of the observed genetic variation in the population (Cogan et al ., 2002). The QTL on linkage group O1, which alone accounted for 15% of the observed genetic variation, was shown to have no effect on adventitious (non‐transgenic) root production, whereas the QTL on linkage groups O3 and O7 controlled both transgenic and adventitious root production.…”

Genetic analysis of Agrobacterium tumefaciens susceptibility in Brassica oleracea

“…The A12DHd/GDDH33 population has also been screened for adventitious and transgenic root production following inoculation with Agrobacterium rhizogenes (Cogan et al 2002). Three QTL were identified for adventitious root production on linkage groups O3, O5 and O7, and QTL associated with transgenic root production were assigned to linkage groups O1, O3 and O7.…”

Production of Transgenic Vegetable Brassicas

“…Sparrow et al (2003) investigated the genetic basis of two key variables of A. tumefaciens-mediated transformation in broccoli. Cogan et al (2002) studied GFP expression after A. rhizogenes-mediated transformation in 73 lines of a Chinese kale ¥ broccoli DH mapping population. They mapped quantitative trait loci (QTL) associated with Agrobacterium susceptibility and demonstrated the ability to introduce increased shoot regeneration potential and susceptibility to Agrobacterium into otherwise recalcitrant lines.…”