Chenopodium album is a predominantly self-fertilising weed species common in temperate regions of the world that has developed resistance to photosystem II inhibitors. The genetic variation and population structure of eight populations from North West Europe were investigated using 416 amplified fragment length polymorphism (AFLP) markers. The populations were checked for their level of herbicide resistance by pot experiments and the investigated plants were genotyped for the Ser 264 to Gly mutation by cleaved amplified polymorphic sequence. Five populations were sampled in sugar beet, one population from a maize monoculture served as a triazine-resistant reference and the two other populations were susceptible reference populations. NeiÕs gene diversity within populations for the whole dataset was low (0.073), whereas, the differentiation among populations was significant (U ST = 0.26, AMOVA, P < 0.001). There was no correlation between geographical and genetic distance of population pairs. The allelic richness (estimated by Ôband richnessÕ and percentage of polymorphic loci) was lowest in the two populations with a complete set of herbicide-resistant plants and in one population with a mixture of herbicide-resistant and -susceptible plants, giving evidence for a historical bottleneck. However, the loss in genetic variation was not that large, indicating that herbicide-resistant populations may maintain their adaptive capacity. Furthermore, this study shows that different techniques can be used to extract information from AFLP markers for the investigation of the genetic background of weed populations. Knowledge about the origin and spread of herbicide-resistant weed populations may give opportunities to manage the resistance problem, with its associated ecological and economic consequences. REHEUL D (2010). The origin of herbicide-resistant Chenopodium album: analysis of genetic variation and population structure. Weed Research 50, 235-244.

Metamitron metabolism in C. album may act as a basic tolerance mechanism, which can be important in circumstances favouring this degradation pathway.

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Aper J, Mechant E, De Riek J, Van Laere K, Bulcke R & Reheul D (2012). Analysis of local spread of metamitron‐resistant Chenopodium album patches in Belgium. Weed Research52, 421–429. Summary 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 фPT 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.

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