Abstract
Auxinic herbicides (e.g. dicamba) are extensively used in agriculture to selectively control broadleaf weeds. Although cultivated species of Brassicaceae (e.g. Canola) are susceptible to auxinic herbicides, some biotypes of Sinapis arvensis (wild mustard) were found dicamba resistant in Canada. In this research, dicamba tolerance from wild mustard was introgressed into canola through embryo rescue followed by conventional breeding. Intergeneric hybrids between S. arvensis (2n = 18) and B. napus (2n = 38) were produced through embryo rescue. Embryo formation and hybrid plant regeneration was achieved. Transfer of dicamba tolerance from S. arvensis into the hybrid plants was determined by molecular analysis and at the whole plant level. Dicamba tolerance was introgressed into B. napus by backcrossing for seven generations. Homozygous dicamba-tolerant B. napus lines were identified. The ploidy of the hybrid progeny was assessed by flow cytometry. Finally, introgression of the piece of DNA possibly containing the dicamba tolerance gene into B. napus was confirmed using florescence in situ hybridization (FISH). This research demonstrates for the first time stable introgression of dicamba tolerance from S. arvensis into B. napus via in vitro embryo rescue followed by repeated backcross breeding. Creation of dicamba-tolerant B. napus varieties by this approach may have potential to provide options to growers to choose a desirable herbicide-tolerant technology. Furthermore, adoption of such technology facilitates effective weed control, less tillage, and possibly minimize evolution of herbicide resistant weeds.
Highlights
Auxinic herbicides were the first synthetic herbicides discovered and have been in use for several decades in agriculture
Among two embryo rescue protocols used as described by Mithila and Hall [18], strategy II was best for producing B. napus x S. arvensis hybrids (Table 1)
Dicamba tolerance was confirmed by the presence of the M5 molecular marker in all dicamba-tolerant progeny from homozygous BC7F3 line (11-12-8), suggesting a true-breeding dicamba-tolerant line
Summary
Auxinic herbicides were the first synthetic herbicides discovered and have been in use for several decades in agriculture. These herbicides have been a favorite choice among farmers worldwide as they selectively control broadleaf weeds. Despite seven decades of extensive use, only 32 auxinic herbicideresistant biotypes have been documented worldwide [1]; a relatively low number compared to PLOS ONE | DOI:10.1371/journal.pone.0141418. Production of Dicamba-Tolerant Brassica napus are no further patents, products in development or marketed products to declare. This does not alter the authors' adherence to all the PLOS ONE policies on sharing data and materials
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