Warmer summers have the potential to affect food security by increasing the prevalence and activity of Actinobacteria

Climate warming impacts agricultural ecosystems in an unpredictable manner. Below-ground microbes are pivotal for aboveground productivity, but their influences on crop productivity in a warming climate are unknown. We conducted a regional-scale field survey in 253 rice‒wheat rotation systems using bacterial 16S amplicon sequencing and satellite-derived crop net primary productivity (NPP) data to investigate the relationships between soil bacteria and crop NPP under different temperatures. Actinobacteria were identified as the main driver of crop NPP, accounting for 4.2 % of the variation, with summer warming accounting for 11.9 % of the increase in their relative abundance. Summer warming resulted in an increase in antibiotic production genes within Actinobacteria, potentially reducing crop productivity by inhibiting seed germination and root elongation and by suppressing plant growth-promoting microorganisms. Taken together, our study indicates that warmer summers are expected to increase the relative abundance of soil Actinobacteria in rice-wheat rotation systems, which will negatively impact crop NPP due to their production of antibiotics that suppress beneficial plant microbes and/or inhibit crop seed germination and root elongation.