Citrus Cultivar Influences the Response of Rhizosphere Microbial Communities to Drought Stress

Drought stress profoundly impacts citrus growth and soil health, yet the role of rhizosphere microbial communities in plant drought tolerance remains poorly understood. This study investigated the rhizosphere microbial structure, soil enzymatic activities, and physicochemical properties of drought-tolerant (DR) and drought-sensitive (DS) citrus varieties under drought stress condition. High-throughput sequencing revealed that drought significantly altered microbial community composition, enriching for gram-negative, stress-tolerant, and potentially pathogenic bacteria, as well as plant pathogenic fungi, while reducing undefined saprotrophs. Notably, the DR variety exhibited more stable and complex bacterial network, higher enrichment of beneficial fungi like Penicillium and Trichoderma, and unique recruitment of mycorrhizal fungi, which were absent in DS. Furthermore, soil catalase and urease activities downregulated under drought, whereas acid phosphatase activity upregulated, particularly in drought tolerant cultivar. Correlation analyses indicated that these microbial shifts were closely linked to changes in soil nutrient availability. Our findings demonstrate that the drought-tolerant citrus variety modulates its rhizosphere microbiome towards a more cooperative and resilient state, highlighting the critical role of host-specific microbial recruitment enhances plant adaptation to drought stress for sustainable agriculture.