The resistance of the wheat microbial community to water stress is more influenced by plant compartment than reduced water availability

Drought is a serious menace to agriculture across the world. However, it is still not clear how this will affect crop-associated microbial communities. Here, we experimentally manipulated precipitation in the field for two years and compared the bacterial communities associated with leaves, roots, and rhizosphere soils of two different wheat genotypes. The bacterial 16S rRNA gene was amplified and sequenced, while 542 microorganisms were isolated and screened for their tolerance to osmotic stress. The bacterial community was not significantly affected by the precipitation manipulation treatments but differed drastically from one plant compartment to the other. Forty-four isolates, mostly bacteria, showed high levels of resistance to osmotic stress by growing in liquid medium supplemented with 30% polyethylene glycol. The Actinobacteria were overrepresented among these isolates, and in contrast to our expectation, precipitation treatments did not influence the odds of isolating osmotic stress-resistant bacteria. However, the odds were significantly higher in the leaves as compared to the roots, the rhizosphere, or the seeds. Our results suggest that isolation efforts for wheat-compatible water stress resistant bacteria should be targeted at the leaf endosphere and that short-term experimental manipulation of precipitation does not result in a more resistant community.