Tracing spread of weeds with molecular markers can give valuable information on the importance of migration mechanisms. This study investigated the local spread of metamitron-resistant Chenopodium album patches in the west of the province West Flanders (Belgium) using amplified fragment length polymorphism (AFLP) markers. During the summer of 2009, leaf samples of C. album plants were harvested in 27 patches, distributed over 10 sugar beet fields and one maize field. The fields were grouped in four local clusters, each corresponding to a farmer who cultivated these fields. A cleaved amplified polymorphic sequence procedure identified the Ser264 to Gly mutation in the D1 protein, endowing resistance to metamitron, a key herbicide applied in sugar beet. The majority of the sampled plants within a patch (97% on average) carried this mutation. Genetic variation among the four farmers’ locations (12%) and among the C. album patches within the farmers’ locations (14%) was significant according to amova (P < 0.001). In addition, Mantel tests confirmed a positive correlation between genetic distance (linearised ?PT between pairs of patches) and the logarithm of geographic distance for the complete data set (Mantel coefficient significant at P = 0.001), suggesting isolation by distance. Nevertheless, genetic similarity between patches from different fields indicated that seed transport by agricultural machinery and manure is likely to have an important impact on the spread of metamitron-resistant biotypes. Farmers should become aware of the resistance problem as soon as possible, in order to prevent further spread in their fields.
- herbicide resistance, fat-hen, CHEAL, amplified fragment length polymorphism, photosystem II inhibitors, genetic differentiation