Shifts in Bacterial Community Structure and Phosphorus-solubilizing Bacteria Abundance in Rhizosphere of Tibetan Barley along a Gradient of Soil Phosphorus Availability

As the phosphorus (P) availability limits nutrient uptake and yield of crop plants, there is an urgent need to explore more P-solubilizing microorganisms and the influencing factors of their abundance in the field. However, it remains unclear how environmental and plant-related factors affect both total bacterial community and P-solubilizing bacteria in various P regime. In this study, we characterized the rhizosphere bacterial communities of Tibetan barley at 29 sites (classified into four soil types with varying AP contents) in a field survey as well as different barley origins in a field control experiment (located in Lasa and Linzhi) in China. We identified the P-solubilizing capacity of isolated bacterial strains in vitro and explored their distribution and relative abundance in the bacterial communities of Tibetan barley plants across sites and soil types. Our results found that Bacillus and Pseudomonas bacteria with the P-solubilizing capacity could be widely distributed in the rhizosphere of barley plants at different sites. Relative abundance of P-solubilizing bacteria and bacterial community structure, including the relative abundance of both dominant phyla and genera, OTUs richness, and Shannon index, varied greatly among the four soil types and was also related with soil available P content. These parameters were only affected by experimental location rather than plant seed origin, mainly due to a stronger influence of soil conditions in shaping root-associated bacterial community compared to plant-related factors. Overall, our study highlights the necessity of combining field survey and experimental approaches to explore the underlying mechanisms of plant-soil microorganism interactions.