Profiling of farmland microorganisms in maize and minor-grain crops under extreme drought conditions

Soil microorganisms are ubiquitous in farmland, however, knowledge regarding the drought resistance of minor grain crops from the perspective of root-associated microbial communities is still poorly understood. We investigated the composition, diversity, co-occurrence network, and assembly process of bacterial and fungal communities in rhizosphere and root of sorghum, broomcorn millet, and foxtail millet under extreme drought conditions, with widely planted maize as the control. These results showed that Firmicutes and Proteobacteria were enriched in rhizosphere and root of broomcorn millet, respectively, and the relative abundances of Sordariomycetes and Eurotiomycetes, and bacterial alpha diversity in rhizosphere and root of sorghum were the larger than those of the other three crops, which was attribute to the lowest contents of organic matter (OM) and total nitrogen (TN). The bacterial network of broomcorn millet and fungal network of foxtail millet were more complex than those of maize, showing higher nodes, edges, density, and average degree. The NTI values of bacterial community in rhizosphere and root of broomcorn millet were greater than those of maize, indicating broomcorn millet had closer phylogenetic relationships. This study revealed the significant advantages of planting minor-grain crops from the perspectives of microorganisms under extreme drought conditions, which can be used to optimize the planting management strategies of farmland.