Soil water stress history wheat microbiome. soil metagenome

Even though some plant-associated microbes are known to help plants to cope with water stress, there is little understanding about how soil water stress history and host genotype influence the response of wheat-associated microbiome under short-term decreases in soil moisture. To address this, we investigated how plant breeding history (four wheat genotypes; two with recognized drought resistance and two without) and soil water stress history (same wheat field soil from Saskatchewan with contrasting long-term irrigation) independently or interactively influenced the response of the rhizosphere, root and leaf bacterial and fungal microbiota to short-term decreases in soil moisture. We combined amplicon sequencing (16S rRNA gene for bacteria and ITS region for fungi) with real-time PCR (qPCR) to quantitatively characterize the wheat microbiome. Fungal and bacterial communities responses to short-term decreases in soil water content were mainly constrained by soil water stress history, with some smaller, but significant influence of plant genotype. One exception was the leaf-associated fungal communities, for which the largest constraint was genotype, resulting in a clear differentiation of the communities based on the genotype’s sensitivity to water stress. Interpreting the data based on relative or estimated absolute abundances revealed substantial discrepancies, suggesting that important shifts might be missed using compositional data derived from amplicon sequencing. Overall, the results from this study highlight that both plant and soil histories need to be taken into consideration when trying to understand the response of plant-associated microbiome to short-term decreases in soil moisture.