Genotype-Specific Root Plasticity and Microbial Recruitment Partnerships Drive Phosphorus Acquisition in Cotton Under Low Phosphorus Stress

Phosphorus (P) scarcity is a major constraint to crop productivity due to its low bioavailability in soils. While plant-microbe interactions play a crucial role in enhancing P acquisition, their mechanisms remain poorly understood, particularly in economically important crops like cotton. This study investigated how low-P-tolerant (BX014) and sensitive (DLNTDH) cotton genotypes adapt to P deficiency by modifying root morphology, exudation patterns, and rhizosphere microbiota to optimize P utilization. A 60-day pot experiment with four P levels (0.01-0.5 g kg-1) was conducted to assess agronomic performance, root traits, organic acid anions (OAA) exudation, soil enzyme activity, and bacterial community dynamics using 16S rRNA sequencing and structural equation modeling (SEM). Results revealed that under low-P stress (P0), BX014 exhibited superior root plasticity, increased OAA exudation (formic, malic, lactic, acetic acid), and enhanced soil enzyme activity (S_ACP, S_UR, S_LAP ). These adaptations facilitated the recruitment of beneficial microbial taxa (Proteobacteri, Actinobacteria), leading to a 48.3% increase in P-use efficiency (PUE) compared to DLNTDH. SEM analysis confirmed that root exudates, microbial biomass, and soil enzyme activity collectively contributed to PUE, explaining 91% of the biomass variation in BX014. These findings highlight genotype-specific strategies to mitigate P limitation through root-microbe interactions. Leveraging such natural synergies could enhance sustainable agriculture by reducing fertilizer dependence and improving resilience in nutrient-deficient soils.