Gene Flow and Multiple Herbicide Resistance in Escaped Canola Populations

Abstract

Gene flow among herbicide-resistant (HR) canola varieties can lead to the development of multiple HR canola plants, creating volunteer canola management challenges for producers. In western Canada, escaped populations of HR canola are ubiquitous outside of cultivated fields, yet the extent of gene flow resulting in herbicide resistance trait stacking in individuals within these populations remains unknown. The objectives of this study were to document the presence of single and multiple herbicide resistance traits and assess the extent of gene flow within escaped canola populations. Seed was collected from 16 escaped canola populations along the verges of fields and roadways in four agricultural regions in southern Manitoba from 2004 to 2006. Glyphosate resistance was found in 14 (88%) of these populations, glufosinate resistance in 13 (81%) populations, and imidazolinone resistance in five (31%) populations. Multiple herbicide resistance was observed at levels consistent with previously published canola outcrossing rates in 10 (62%) of the tested populations. In 2005 and 2006, maternal plants from two escaped populations were tested using trait indicator test strips for glyphosate and glufosinate resistance to confirm outcrossing events. In 2005, two of 13 tested maternal plants with single herbicide resistance traits produced progeny with both glyphosate and glufosinate resistance. In 2006, of 21 tested plants, 10 single HR maternal plants produced multiple HR progeny, and five nonresistant maternal plants produced resistant offspring. This is the first report indicating that intraspecific gene flow results in stacking of herbicide resistance traits in individuals within escaped canola populations, confirming that multiple HR canola volunteers are not confined to agricultural fields. Results of this study suggest that escaped populations of crop plants can contribute to the spread of genetically engineered novel traits, which has important implications for containment, especially for highly controversial pharmaceutical and industrial traits in crop plants.

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

“…The feral 10 | P a g e two to three times higher than those observed in Selommes, while in western Canada, the seed yield from individual feral plants was comparable to that of the crop (Knispel et al, 2008).…”

“…In a continuation of the study by Charters et al (1999), it was observed that one population contained, over a period of twelve years, a genetic signature of a variety that had been obsolete for at least ten of those years. In contrast, based on a preliminary analyses of soil samples at feral oilseed rape roadside sites in western Canada in the greenhouse, Knispel et al (2008) indicated that feral oilseed rape roadside soil seedbanks are small (less than five viable seeds per square metre) and lack substantive dormancy. In total, however, the observations from Europe indicate that feral populations have been sufficiently consistent in their presence and abundance to act as a genetic bridge between past and current oilseed rape varieties.…”

“…While many feral populations observed over multiple years were transient at a local scale (e.g., Crawley and Brown, 1995, 2004;Knispel et al, 2008), this apparent transience is likely counterbalanced at a landscape scale by repeated seed addition and redistribution from various sources. Local declines or extinctions in feral populations are likely to be temporary and asynchronous at large spatial scales (Charters et al, 1999; Crawley and Brown, 2004;Peltzer et al, 2008;Knispel and McLachlan, 2009;Nishizawa et al, 2009).…”

“…In regions where GMHT oilseed rape is widely grown such as western Canada and the USA, monitoring surveys confirmed the widespread occurrence of feral GMHT oilseed rape plants along field margins of agricultural fields, as well as along transportation routes (such as road verges and railway lines). In the study of Yoshimura et al (2006), approximately 2/3 of the ferals sampled were transgenic, whereas all ferals sampled by Knispel et al (2008) exhibited the presence of the GLY or GLU tolerance traits (or both). In North Dakota (USA), 347 of the 406 oilseed rape plants collected, tested positive for the GLY or GLU tolerance trait (Schafer et al, 2010).…”

“…These data indicate that feral GMHT oilseed rape will be present along roadsides and other ruderal habitats in areas where GMHT oilseed rape is commercially grown or at points from where it is exported. The frequency of transgenes corresponds 11 | P a g e approximately to the proportion of oilseed rape grown or in transit that is transgenic (Yoshimura et al, 2006;Knispel et al, 2008).In regions where GMHT oilseed rape is currently not grown commercially, surveys, for example performed in and around major ports and along roads leading from these ports to inland processing facilities in Japan, revealed that feral oilseed rape plants can express/contain the GLY or GLU tolerance trait, and to a lesser extent both traits ( …”