Genetic variation was assessed in a range of populations of wild mustard (Sinapis arvensis L.) using random amplified polymorphic DNA (RAPD) analysis. Sixty markers were used to assess the extent of genetic variation in wild mustard populations sampled throughout 12 different locations in the United Kingdom, including herbicide treated and untreated sites. In addition, selected sites were sampled over two consecutive seasons. Individual plant analysis was required, since a high degree of intra-population genetic variation was observed. The apparent extent of genetic variation in a population at one site increased when the results from two consecutive seasons were assessed. The range of genetic variation was as high in the herbicide-treated populations as in those which were untreated. Genetic diversity was maintained in populations of wild mustard where rotational cropping and herbicide use was practiced. These results confirm the utility of RAPD for the determination of genetic variation in outcrossing species where no prior genotypic knowledge is available.
