Potential gene flow of two herbicide-tolerant transgenes from oilseed rape to wild B. juncea var. gracilis

Abstract

Four successive reciprocal backcrosses between F(1) (obtained from wild Brassica juncea as maternal plants and transgenic glyphosate- or glufosinate-tolerant oilseed rape, B. napus, as paternal plants) or subsequent herbicide-tolerant backcross progenies and wild B. juncea were achieved by hand pollination to assess potential transgene flow. The third and forth reciprocal backcrosses produced a number of seeds per silique similar to that of self-pollinated wild B. juncea, except in plants with glufosinate-tolerant backcross progeny used as maternal plants and wild B. juncea as paternal plants, which produced fewer seeds per silique than did self-pollinated wild B. juncea. Germination percentages of reciprocal backcross progenies were high and equivalent to those of wild B. juncea. The herbicide-tolerant first reciprocal backcross progenies produced fewer siliques per plant than did wild B. juncea, but the herbicide-tolerant second or third reciprocal backcross progenies did not differ from the wild B. juncea in siliques per plant. The herbicide-tolerant second and third reciprocal backcross progenies produced an amount of seeds per silique similar to that of wild B. juncea except for with the glufosinate-tolerant first and second backcross progeny used as maternal plants and wild B. juncea as paternal plants. In the presence of herbicide selection pressure, inheritance of the glyphosate-tolerant transgene was stable across the second and third backcross generation, whereas the glufosinate-tolerant transgene was maintained, despite a lack of stabilized introgression. The occurrence of fertile, transgenic weed-like plants after only three crosses (F(1), first backcross, second backcross) suggests a potential rapid spread of transgenes from oilseed rape into its wild relative wild B. juncea. Transgene flow from glyphosate-tolerant oilseed rape might be easier than that from glufosinate-tolerant oilseed rape to wild B. juncea. The original insertion site of the transgene could affect introgression.

A Dominant Point Mutation in a RINGv E3 Ubiquitin Ligase Homoeologous Gene Leads to Cleistogamy inBrassica napus

“…The vast majority of cultivated oilseed rape cultivars are self-compatible and allogamous, with an outcrossing rate ranging between 12 and 55% (average 30%), depending on the genotype and environmental conditions , although both of its diploid progenitors are self-incompatible (Silva and Goring, 2001). B. napus can disseminate its pollen as well as receive pollen from quite distantly related plants, including wild related species (Jørgensen and Andersen, 1994;Halfhill et al, 2002;Warwick et al, 2003;Ammitzbøll and Bagger Jørgensen, 2006;Ford et al, 2006;Song et al, 2010). …”

Possibilities of direct introgression from <i>Brassica napus</i> to <i>B. juncea</i> and indirect introgression from <i>B. napus</i> to related Brassicaceae through <i>B. juncea</i>

“…Fertility of BC 1 , BC 2, and BC 3 generations from F 1 ( B. juncea × B. napus ) × B. juncea was reported by Song et al (2010) and Tsuda et al (2012b). Seed productivities of BC 2 and BC 3 were promptly recovered to the same level as those of the parent lines (Table 5).…”

“…Female fertility of the F 1 hybrids was assessed by comparative analysis of the productivity of BC 1 seeds using backcrossing (Table 4). Seed productivity of BC 1 was remarkably reduced compared with that of both parents (Choudhary and Joshi 2001, Frello et al 1995, Heenan et al 2007, Kirti et al 1995, Liu et al 2010, Mathias 1985, Roy 1984, Schelfhout et al 2006, Song et al 2010), which was indicative of the degradation of female and male fertility of F 1 .…”

Biotechnology: Herbicide-Resistant Crops

“…Yet, all combinations of these resistances have been found in individual volunteer canola plants, both outside and within canola fields (Knispel et al, 2008;Schafer et al, 2012b). Gene flow can also occur between glufosinate-resistant canola and weedy relatives (Song et al, 2010). Fully introgressed bar genes into weeds have not been documented.…”