Gene flow between imidazolinone‐tolerant and – susceptible winter oilseed rape varieties

Abstract

Krato C & Petersen J (2012). Gene flow between imidazolinone‐tolerant and – susceptible winter oilseed rape varieties. Weed Research 52, 187–196.SummaryImidazolinone‐tolerant (IT) spring oilseed rape was developed in 1987 using conventional breeding methods and first marketed in Canada in 1996. IT winter oilseed rape will be introduced into the European market. On the one hand, the IT cropping system provides the opportunity for post‐emergence weed control in oilseed rape. On the other hand, the introduction of a new herbicide‐tolerance (HT) trait into the European cropping systems may lead to new challenges for weed control in crop rotations containing winter oilseed rape. In this study, a 2‐year field and glasshouse study was carried out to determine the transfer frequency of the HT trait from IT winter oilseed rape plants to adjacently grown susceptible winter oilseed rape plants. Furthermore, cross‐resistance to sulfonylureas and differences in herbicide response of heterozygous and homozygous IT winter oilseed rape varieties to triflusulfuron‐methyl were examined. The transfer frequency of the resistance trait and zygosity of the F1‐generation was investigated using a real‐time quantitative polymerase chain reaction (qPCR). Outcrossing frequencies ranged from 2.05% in a westerly direction and 0.57% in an easterly direction at the closest distance of 2 m between pollen donor (IT oilseed rape plants) and pollen acceptor (imidazolinone‐susceptible plants). Outcrossing events decreased significantly with increasing distance from the pollen donor, but IT F1‐plants were still found at a distance of 45 m. Of the analysed F1‐oilseed rape plants, 84% showed both independent tolerance genes for imidazolinone‐tolerance (PM1 and PM2) and were heterozygous for both genes. IT winter oilseed rape plants showed a cross‐tolerance against triflusulfuron‐methyl, and the corresponding resistance factors were higher for homozygous biotypes compared with heterozygous ones. Consequently, outcrossing can result practically in IT volunteers with cross‐tolerance to triflusulfuron‐methyl.