The origin of herbicide-resistant Chenopodium album: analysis of genetic variation and population structure

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. Nei's gene diversity within populations for the whole dataset was low (0.073), whereas, the differentiation among populations was significant ((ST) = 0.26, amova, P <0.001). There was no correlation between geographical and genetic distance of population pairs. The allelic richness (estimated by 'band richness' 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