title: Growth, productivity, and competitiveness of introgressed weedy Brassica rapa hybrids selected for the presence of Bt cry1Ac and gfp transgenes.
abstract: Concerns exist that transgenic crop x weed hybrid populations will be more vigorous and competitive with crops compared with the parental weed species. Hydroponic, glasshouse, and field experiments were performed to evaluate the effects of introgression of Bacillus thuringiensis (Bt) cry1Ac and green fluorescent protein (GFP) transgenes on hybrid productivity and competitiveness in four experimental Brassica rapa x transgenic Brassica napus hybrid generations (F1, BC1F1, BC2F1 and BC2F2). The average vegetative growth and nitrogen (N) use efficiency of transgenic hybrid generations grown under high N hydroponic conditions were lower than that of the weed parent (Brassica rapa, AA, 2n = 20), but similar to the transgenic crop parent, oilseed rape (Brassica napus, AACC, 2n = 38). No generational differences were detected under low N conditions. In two noncompetitive glasshouse experiments, both transgenic and nontransgenic BC2F2 hybrids had on average less vegetative growth and seed production than B. rapa. In two high intraspecific competition field experiments with varied herbivore pressure, BC2F2 hybrids produced less vegetative dry weight than B. rapa. The competitive ability of transgenic and nontransgenic BC2F2 hybrids against a neighbouring crop species were quantified in competition experiments that assayed wheat (Triticum aestivum) yield reductions under agronomic field conditions. The hybrids were the least competitive with wheat compared with parental Brassica competitors, although differences between transgenic and nontransgenic hybrids varied with location. Hybridization, with or without transgene introgression, resulted in less productive and competitive populations.
authors.affiliation: University of Tennessee, Department of Plant Sciences, Knoxville, TN 37996-4561, USA.
authors.forename: Matthew D
authors.initials: MD
authors.lastname: Halfhill
authors.forename: Jamie P
authors.initials: JP
authors.lastname: Sutherland
authors.forename: Hong Seok
authors.initials: HS
authors.lastname: Moon
authors.forename: Guy M
authors.initials: GM
authors.lastname: Poppy
authors.forename: Suzanne I
authors.initials: SI
authors.lastname: Warwick
authors.forename: Arthur K
authors.initials: AK
authors.lastname: Weissinger
authors.forename: Thomas W
authors.initials: TW
authors.lastname: Rufty
authors.forename: Paul L
authors.initials: PL
authors.lastname: Raymer
authors.forename: C Neal
authors.initials: CN
authors.lastname: Stewart
mesh_terms: D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins / Q000235:genetics*; D001427:Bacterial Toxins / Q000235:genetics*; D029688:Brassica napus / Q000235:genetics* / Q000254:growth & development*; D029741:Brassica rapa / Q000235:genetics* / Q000254:growth & development*; D003433:Crosses, Genetic; D004731:Endotoxins / Q000235:genetics*; D049452:Green Fluorescent Proteins / Q000235:genetics*; D006460:Hemolysin Proteins; D018515:Plant Leaves / Q000254:growth & development; D030821:Plants, Genetically Modified / Q000235:genetics / Q000254:growth & development*; D011897:Random Allocation; D014908:Triticum / Q000254:growth & development
chemical_list: D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins; D001427:Bacterial Toxins; D004731:Endotoxins; D006460:Hemolysin Proteins; C030956:insecticidal crystal protein, Bacillus Thuringiensis; D049452:Green Fluorescent Proteins