High Salt Levels Reduced Dissimilarities in Root-Associated Microbiomes of Two Barley Genotypes

Plants harbour in and at their roots bacterial microbiomes that contribute to their health and fitness. The microbiome composition is controlled by the environment and plant genotype. Previously, it was shown that the plant genotype-dependent dissimilarity of root microbiome composition of different species becomes smaller under drought stress. However, it remains unknown whether this reduced plant genotype-dependent effect is a specific response to drought stress or a more generic response to abiotic stress. To test this, we studied the effect of salt stress on two distinct barley (Hordeum vulgare L.) genotypes; the reference cultivar Golden Promise and the Algerian landrace AB. As inoculum, we used soil from a salinized and degraded farmland on which barley was cultivated. Controlled laboratory experiments showed that plants inoculated with this soil display growth stimulation under high salt stress (200mM) in a plant genotype-independent manner, whereas the landrace AB also showed significant growth stimulation at low salt concentrations. Subsequent analysis of the root microbiomes revealed a reduced dissimilarity of the bacterial communities of the two barley genotypes in response to high salt, especially in the endophytic compartment. High salt level did not reduce α-diversity (richness) in the endophytic compartment of both plant genotypes, but associates with an increased number of shared strains that respond positively to high salt. Among these, Pseudomonas species were most abundant. These findings suggest that the plant genotype-dependent microbiome composition is altered generically by abiotic stress.