Mucilage produced by sorghum (Sorghum bicolor) aerial roots supports a nitrogen-fixing community

Summary Sorghum ( Sorghum bicolor ) is gaining popularity as a sustainable energy crop due to its high biomass and potential for biofuel production. Some rare sorghum accessions develop many aerial roots that produce viscous carbohydrate-rich mucilage after rain. This aerial root mucilage is strikingly similar to that observed in specific landraces of maize ( Zea mays ) from southern Mexico, which have been previously shown to host nitrogen-fixing bacteria (diazotroph). The landraces displaying these traits can reduce nitrogen-based fertilizer input, mitigating their negative environmental impacts. In this study, we characterized the aerial root development of several sorghum accessions and successfully isolated more than 103 distinct diazotrophs from the sorghum mucilage. Using acetylene reduction and 15 N gas enrichment assays, we confirmed that sorghum plants acquire nitrogen from the atmosphere through the diazotrophic associations in the mucilage. This sorghum symbiotic relationships with diazotrophs offer a promising avenue for nitrogen fixation, potentially diminishing reliance on synthetic fertilizers and promoting sustainable agricultural practices.