Drought legacy enhances tea plant drought tolerance by modulating the rhizosphere core microbiota

Drought limits the cultivation and quality of tea plants, and the drought legacy effect will affect the drought tolerance of plants. However, there are few studies on the effects of drought legacy on tea plants. In this experiment, a two-stage pot culture method was used to test the drought legacy effect. The effects of drought legacy on tea plants were studied by physiological index determination and 16S rRNA gene high-throughput sequencing. The residual impact of drought conditions led to an increase in the root-to-shoot ratio of tea seedlings. Specifically, the root-to-shoot ratio in the DRY-D was 55.26% higher compared to the WET-D, accompanied by significant elevations in the levels of ABA, IAA, and TZR. Furthermore, drought residual effects induced notable alterations in the rhizosphere bacterial communities across treatments, with particular operational taxonomic units (OTUs) driving the restructuring of these microbial assemblages. Notably, the relative abundance of 54 OTUs differed significantly between DRY-D and WET-D. The drought residual effect also influenced the rhizosphere bacterial network of tea seedlings, which exhibited characteristics of a 'small-world' network and a modular architecture. Across all treatments, bacterial communities were predominantly governed by positive interactions and demonstrated considerable stability; however, the degree of cohesion among communities varied. In the WET-W, bacterial communities were primarily characterized by mutualistic interactions, whereas in WET-D, competitive interactions were intensified, thereby diminishing the predominance of positive interactions. The DRY-W displayed a balance between positive and negative bacterial interactions, while in DRY-D, positive interactions predominated. Core bacterial taxa were identified in each treatment, with 13, 5, 14, and 4 core bacteria detected in WET-W, WET-D, DRY-W, and DRY-D, respectively. These core bacteria functioned as central 'connection hubs' within the overall bacterial network, with those in the DRY-D treatment playing a critical role in maintaining the integrity and stability of the microbial network. Drought legacy enhanced tea drought tolerance via restructuring rhizosphere core microbiota that optimize hormonal balance and root growth, providing a basis for using microbial inoculation to improve tea drought resistance against climate change.