Barley cultivars shape the abundance, phenotype, genotype and gene expression of their associated microbiota by differential root exudate secretion

Abstract

AbstractPlant associated microbes play vital roles in promoting plant growth and health, with plants secreting root exudates into the rhizosphere to attract beneficial microbes. Exudate composition defines the nature of microbial recruitment, with different plant species attracting distinct microbiota to enable optimal adaptation to the soil environment. To more closely examine the relationship between plant genotype and microbial recruitment, we analysed the rhizosphere microbiomes of landrace (Chevallier) and modern (NFC Tipple) barley cultivars. Distinct differences were observed between the plant-associated microbiomes of the two cultivars, with the plant-growth promoting rhizobacterial genusPseudomonassubstantially more abundant in the Tipple rhizosphere. Striking differences were also observed between the phenotypes of recruitedPseudomonaspopulations, alongside distinct genotypic clustering by cultivar. Cultivar-drivenPseudomonasselection was driven by root exudate composition, with the greater abundance of hexose sugars secreted from Tipple roots attracting microbes better adapted to growth on these metabolites, and vice versa. Cultivar-driven selection also operates at the molecular level, with both gene expression and the abundance of ecologically relevant loci differing between Tipple and ChevallierPseudomonasisolates. Finally, cultivar-driven selection is important for plant health, with both cultivars showing a distinct preference for microbes selected by their genetic siblings in rhizosphere transplantation assays.