Molecular detection and quantification of the seedbank in agricultural soils.

(Del.) Benth is a devastating parasitic weed in Sub-Saharan Africa (SSA) and its soil seedbank is the major factor contributing to its prevalence and persistence. To date, there is a little information on the seedbank density in agricultural fields in SSA due to the lack of reliable detection and quantification methods. We developed a high-throughput method that combines density- and size-based separation techniques with quantitative polymerase chain reaction (qPCR)-based detection of seeds in soil. The method was optimised and validated by introducing increasing numbers of seeds in two physicochemically different -free agricultural soils. The results showed that as little as one seed of per 150 g of soil could be detected. This technique was subsequently tested on soil samples of 48 sorghum fields from different agro-ecological zones in Ethiopia to map the geospatial distribution of the seedbank along a trajectory of more than 1500 km. Considerable variation in seed densities was observed. seeds were detectable in 75% of the field soils with densities up to 86 seeds per 150 g of soil. The seed density in soil and the number of emerged plants in the field showed a non-linear relationship. In conclusion, the method developed allows for accurate mapping of the seedbank in physicochemically diverse SSA field soils and can be used to assess the impact of management strategies on seedbank dynamics.