Gene flow between oilseed rape (Brassica napus L. oleifera) and black mustard (Brassica nigra L.)

Over the past decade, plant genetic engineering techniques have been developed where specific characters (genes) can be introduced into a plant in a relatively straightforward manner, provided the genes coding for the character have been identified. Canola crops (Brassica napus L.) can suffer severe yield loss due to weed infestation. Since Brassica species can be readily transformed, and specific genes have been identified for herbicide resistance, it is no surprise that genetic engineers have targeted herbicide resistance in canola. (Moloney et al., 1989). A major concern of introducing herbicide resistant crops into agriculture is the spread of the engineered gene, particularly by pollen, to related weed species. The opportunity for gene escape via hybridization depends upon the presence of wild relatives capable of crossing with the crop under natural conditions (Ellstrand, 1988). There is substantial recent literature on intergeneric crosses within the Brassicaceae family, and an even larger number on hybridization between different Brassica species. Most of these hybrids do not produce mature seed; however normally incompatible interspecific hybridization can spontaneously produce a few seeds which usually yield true F1 plants as a result of unexpected ploidy changes (Nashiyama et al., 1991) This phenomenon has been documented between B. napus and B. nigra. The objectives of the present study were to determine the feasibility and frequency of gene flow between canola (B. napus) and a related weed species (B. nigra) by means of ISSR (Inter Simple Sequence Repeat) markers.