Disentangling the importance of microbiological and physico-chemical properties of Ethiopian field soils for the Striga seed bank and sorghum infestation

Background: Striga hermonthica (Striga) is a parasitic weed that severely affects sorghum yield in sub-Saharan Africa. Recent studies highlighted the soil microbiome’s potential to suppress Striga through interference with specific stages in its life cycle. Results: Statistical analyses of data collected from 48 Ethiopian sorghum field soils sampled across a > 1000-km-transect revealed that microbial communities and their interactions with soil physico-chemical properties correlated with Striga occurrence in the field. Striga infestation of sorghum and seedbank levels were negatively correlated with potassium and sulfur soil content and positively correlated with calcium and magnesium nutrient profile proportions. Microbiome analyses indicated that fungal communities were more responsive than bacteria to changes in Striga infestation and seedbank levels, with distinct microbial composition even in soils where Striga was not detected. Specific fungal and bacterial genera showed both positive and negative correlations with Striga measures, but patterns rarely held across taxonomic levels. To begin to validate these correlations, we tested an isolate from the fungal genus Neocosmospora, which negatively correlated with the Striga seedbank, and showed that this isolate promotes Striga seed germination in vitro. The data and analysis methods are integrated and shared in a public Shiny App for broader analysis and continued research on soil-Striga interactions. Conclusions: This study highlights the complexity of soil-microbiome-Striga interactions and the potential for observational studies to reveal candidates for biological control of Striga.