Untargeted metabolomics unveils an accumulation of flavonoids associated with the microbiome of low-performing sorghum

The plant metabolome wields a strong influence on its associated microbiome, with feedback from the microbiome in turn influencing plant resilience and productivity. The root metabolome represents a key element of the chemical signaling that influences microbiome recruitment to plants. We examined how the root metabolome differs between high- and low-performing genotypes of a drought-resilient cereal, Sorghum bicolor L. Moench, and how these differences relate to the root microbiome in field-grown plants. Overall, lower-performing genotypes exhibited a distinct root metabolome from higher-performing genotypes. In particular, lower-performing genotypes exhibited an accumulation of flavonoids, a class of secondary metabolites involved in plant defense and stress response. Network analyses revealed microbes whose abundance covaried with flavonoid content and suggested that higher levels of flavonoids may hinder root colonization by specific microbes. Higher-performing genotypes further exhibited more discriminating metabolites with distinct levels between watering treatments as compared to lower-performing genotypes, pointing to the potential of higher performing genotypes to better cope with stress by modulating their microbiomes via root chemistry. We discuss how insights into crop performance from the lens of metabolomics can improve our knowledge of how crops may more effectively recruit beneficial plant microbiomes.