Domestication caused taxonomical and functional shifts in the wheat rhizosphere microbiota, and weakened the natural bacterial biocontrol against fungal pathogens

Modern crops might have lost some of their functional traits, required for interacting with beneficial microbes, as a result of the genotypic/phenotypic modifications that occurred during domestication. Here, we studied the bacterial and fungal microbiota in the rhizosphere of two cultivated wheat species (Triticum aestivum and T. durum) and their respective ancestors (Aegilops tauschii and T. dicoccoides), in three experimental fields, by using metabarcoding of 16S rRNA genes and ITS2, coupled with co-occurrence network analysis. Moreover, the abundance of bacterial genes involved in N- and P-cycles was estimated by quantitative PCR, and urease, alkaline phosphatase and phosphomonoesterase activities were assessed by enzymatic tests. The relationships between microbiota and environmental metadata were tested by correlation analysis. The assemblage of core microbiota was affected by both site and plant species. No significant differences in the abundance of potential fungal pathogens between wild and cultivated wheat species were found; however, co-occurrence analysis showed more bacterial–fungal negative correlations in the wild species. Concerning functions, the nitrogen denitrification nirS gene was consistently more abundant in the rhizosphere of A. tauschii than T. aestivum. Urease activity was higher in the rhizosphere of each wild wheat species in at least two of the research locations. Several microbiota members, including potentially beneficial taxa such as Lysobacter and new taxa such as Blastocatellaceae, were found to be strongly correlated to rhizospheric soil metadata. Our results showed that a functional microbiome shift occurred as a result of wheat domestication. Notably, these changes also included the reduction of the natural biocontrol potential of rhizosphere-associated bacteria against pathogenic fungi, suggesting that domestication disrupted the equilibrium of plant-microbe relationships that had been established during million years of co-evolution.