Status of feral oilseed rape in Europe: its minor role as a GM impurity and its potential as a reservoir of transgene persistence

Abstract

Feral oilseed rape is not a relevant source of macroscopic impurity at its present density in the landscape but provides opportunity for genetic recombination, stacking of transgenes and the evolution of genotypes that under strong selection pressure could increase and re-occupy fields to constitute an economic weed burden and impurity in future crops.

Feral genetically modified herbicide tolerant oilseed rape from seed import spills: are concerns scientifically justified?

“…A 10-year survey (1993)(1994)(1995)(1996)(1997)(1998)(1999)(2000)(2001)(2002), along road verges of a motorway revealed that most quadrats showed transient populations lasting one to four years (Crawley and Brown, 2004). These data and data from other demographic studies indicate a substantial turnover of populations of feral oilseed rape: only a small percentage of populations occurs at the same location over successive years, whereas the majority appears to die out rapidly (Crawley and Brown, 1995, 2004;Charters et al, 1999;Peltzer et al, 2008;Elling et al, 2009;Knispel and McLachlan, 2009;Nishizawa et al, 2009;Squire et al, 2011). However, if habitats are disturbed on a regular basis by anthropogenic activities such as mowing, herbicide applications or soil disturbance, or natural occurrences such as flooding, then feral populations can persist for longer periods (Claessen et al, 2005a;.…”

“…Demographic data on feral oilseed rape in different EU locations showed consistently that persistence in the soil seedbank allowed plants to recur after an absence of a year or more, while several populations persisted for two to four years (Squire et al, 2011). For the study site of Selommes, Pivard et al (2008a) estimated that up to 40% of the observed feral populations persisted mainly through seed emerging from the soil seedbank.…”

“…The size of such populations ranges from single plants to stands of over 1,000 plants with the majority of populations containing 100 plants or less (Squire et al, 2011). Comparisons of five demographic studies of feral oilseed rape in different EU locations (Denmark, Germany (2), France and the UK), constituting over 1,500 ha and 16 site-years of observations, showed that feral populations generally occur at relatively low densities, with a mean around one population per square kilometre, rising to 15 per square kilometre in areas with a high frequency of oilseed rape cultivation such as the study site at Selommes, Loir-et-Cher, France (Lecomte et al, 2007;Messéan et al, 2009;Squire et al, 2011).…”

“…Comparisons of five demographic studies of feral oilseed rape in different EU locations (Denmark, Germany (2), France and the UK), constituting over 1,500 ha and 16 site-years of observations, showed that feral populations generally occur at relatively low densities, with a mean around one population per square kilometre, rising to 15 per square kilometre in areas with a high frequency of oilseed rape cultivation such as the study site at Selommes, Loir-et-Cher, France (Lecomte et al, 2007;Messéan et al, 2009;Squire et al, 2011). The spatial variation in feral populations in part reflects differences in frequency of oilseed rape cultivation and abundance of in-field oilseed rape volunteers in the landscape (Knispel and McLachlan, 2009).…”

“…Secondary dormancy is complex: it can be induced by a range of factors such as low temperature, soil dryness, and darkness through burial in soil (López-Granados and Lutman, 1998;Squire, 1999;Marshall et al, 2000;Momoh et al, 2002;Gruber et al, 2004Gruber et al, , 2010Gulden et al, 2004a). Recently, dormant oilseed rape seed has been found in the soil seedbank in non-till systems, indicating that seed can fall dormant on the soil surface, and need not to be buried in the dark (Gruber et al, 2010).Evidence on the contribution of seed from the seedbank is not entirely consistent, however.Biochemical and molecular analyses indicated that feral sites can contain plants with the same varietal profile consistently for at least three years, and can contain varieties last commercially grown three or more years previously (Squire et al, 2011). Since individual varieties of oilseed rape are sown for only a few years before being superseded by new varieties, the existence of markers from previous varieties indicates the possibility they persisted as ferals, provided origins from farm-saved seed or persistent volunteers can be 9 | P a g e ruled out (SIGMEA, 2010).…”