Breeding selection imposed a differential selective pressure on the wheat root-associated microbiome

Abstract

Plants-microbiome associations are the result of millions of years of co-evolution. Due to breeding-accelerated plant evolution in non-native and highly managed soil, plant-microbe links could have been lost. We hypothesized that post-domestication breeding of wheat changed the root-associated microbiome. To test this, we analyzed root-associated fungal and bacterial communities shortly after emergence of seedlings representing a transect of wheat evolution including modern wheat, landraces and ancestors. Numbers of observed microbial taxa were highest in landraces bred in low-input agricultural systems, and lowest in ancestors that had evolved in native soils. The microbial communities of modern cultivars were different from those of landraces and ancestors. Old wheat accessions enriched Acidobacteria and Actinobacteria, while modern cultivars enriched OTUs from Candidatus Saccharibacteria, Verrucomicrobia and Firmicutes. The fungal pathogens Fusarium, Neoascochyta and Microdochium enriched in modern cultivars. Both bacterial and fungal communities followed a neutral assembly model when bulk soil was considered as the source community, but accessions of the ancient Triticum turgidum and T. monococcum created a more isolated environment in their roots. In conclusion, wheat root-associated microbiomes have dramatically changed through a transect of breeding history.

Keywords: bacteria; breeding; fungi; microbiome; root; selective pressure; wheat.