The responses of crop – wildBrassicahybrids to simulated herbivory and interspecific competition: Implications for transgene introgression

Abstract

Brassica rapa grows as a wild and weedy species throughout the world and is the most likely recipient of transgenes from GM oilseed rape. For transgene introgression to occur, the critical step which must be realized, is the formation of an F1 hybrid. Concerns exist that hybrid populations could be more vigorous and competitive compared to the parental species. This study examines the effect of simulated herbivory and interspecific competition on the vegetative and reproductive performance of non-transgenic F1 hybrids and their parental lines. Several vegetative and reproductive performance measures were used to determine the effect of simulated herbivory and competition on the Brassica lines, including leaf length and biomass for herbivory and seedling height and biomass for competition. For defoliation experiments, B. rapa showed little response in terms of leaf length but B. napus and the F1 hybrid responded negatively. Brassica rapa showed elevated biomass responses, but B. napus and the hybrid demonstrated negative responses to defoliation. Defoliation at the cotyledon stage had a slight effect upon final biomass with the F1 hybrid performing significantly worse than B. napus, although seed counts were not significantly different. For the series of competition experiments, hybrids seemed to be more similar to B. rapa in terms of early seedling growth and reproductive measures. The underperformance of hybrid plants when challenged by herbivory and competition, could potentially decrease survivorship and explain the rarity of hybrids in field surveys. However, should transgene introgression occur, the dynamics of hybrids could change radically thus increasing the risk of gene flow from a transgenic oilseed rape crop to the wild recipient.

Pollen transport differs among bees and flies in a human‐modified landscape

“…Spatial heterogeneity in floral resources is therefore lower than that associated with more natural landscapes Tylianakis et al, 2008). This is ideal to examine differentiation in mobility patterns in contrasting pollinator species; (3) B. rapa attracts a diverse assemblage of insects (Feldman, 2006;Rader et al, 2009), displays increased seed set in the presence of insect pollinators (Free, 1993) and is ubiquitous in most agricultural landscapes as a crop/environmental weed (Feldman, 2006;Sutherland et al, 2006); (4) it is capable of forming hybrids with other Brassica species including B. napus and B. juncea (Scheffler & Dale, 1994;Hauser et al, 1998;Stewart, 2002), which are among the first crops to be genetically modified for herbicide resistance (Hauser et al, 1998;Rieger et al, 2002;Allainguillaume et al, 2006).…”

Scientific advice to the European Commission on the internal review submitted under Regulation (EC) No 1367/2006 on the application of the provisions of the Aarhus Convention against the Commission Implementing Decision 2015/687 to authorise genetically modified oilseed rape MON88302

“…However, fitness advantages due to reduced plant damage resulting from insect pest attack (herbivory) cannot be seen independently from other ecological factors that limit plant fitness. Fitness benefits may be offset by deleterious effects of hybridisation or expression of resistance, and will only be of ecological significance if suitable competition-free germination sites are available for recruitment from seed (Crawley and Brown, 1995;Hails et al, 2006;Sutherland et al, 2006). Theoretical studies predict that insect resistant plants might only be able to invade semi-natural habitats in situations where infestation by target insect pests is sufficiently high and the habitat for plant establishment suitable (Damgaard and Kjaer, 2009).…”

Scientific Opinion on application (EFSA‐GMO‐BE‐2011‐101) for the placing on the market of herbicide‐tolerant genetically modified oilseed rape MON 88302 for food and feed uses, import and processing under Regulation (EC) No 1829/2003 from Monsanto

“…Oilseed rape is generally regarded as an opportunistic species, which can take advantage of disturbed sites due to its potential to germinate and capture resources rapidly. In undisturbed natural habitats, oilseed rape lacks the ability to establish stable populations, possibly due to the absence of competition-free germination sites (Crawley et al, 1993(Crawley et al, , 2001Warwick et al, 1999;Hails et al, 2006;Sutherland et al, 2006;Damgaard and Kjaer, 2009). Moreover, in controlled sowings into road verges, field margins and wasteland, very few seedlings survived to maturity due to grazing (e.g.…”