Differential Cadmium Accumulation and Exudation Patterns Drive Distinct Rhizosphere Microbial Communities in Soybean Cultivars

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Page: 102-105

Shivangi¹, Manoj Kumar², and Sajid Parwez³ (Department of Pharmacy, Sona Devi University, Ghatsila, Jharkhand^1,2 and Department of Psychology, Sona Devi University, Ghatsila, Jharkhand³)

Cadmium (Cd) contamination in agricultural soils presents a significant risk to human and animal health through its accumulation in crops (Alloway, 2013). Understanding the plant-level mechanisms that control Cd uptake and translocation is crucial for developing cultivars that minimize this hazard (Lux et al., 2011). This study investigated the physiological and ecological strategies of three soybean cultivars-Westag 97 (high root Cd accumulator), AC X790P (intermediate), and AC Hime (low root Cd accumulator)in response to Cd stress. It was hypothesized that Cd retention in roots is primarily driven by symplastic compartmentalization, which in turn influences the exudation of organic acids, shaping the functional diversity of the rhizosphere bacterial community (Rascio & Navari-Izzo, 2011). To test this, parallel experiments were conducted: a 14-day hydroponic culture quantified Cd distribution and organic acid exudation, while a 30-day soil culture assessed the physiological profiles of rhizosphere bacteria using Biolog® EcoPlates™ (Garland, 1997). Mild Cd stress, defined as a 2530% reduction in biomass, was induced in both systems (30 µM in hydroponics, 40 mg kg⁻¹ in soil) (Sharma et al., 2020). The high-accumulator cultivar, Westag 97, demonstrated greater symplastic compartmentalization of Cd in its roots compared to the low-accumulator AC Hime. While Westag 97 had the highest baseline exudation of citric, succinic, fumaric, and malic acids, the low-accumulator AC Hime exhibited a significantly stronger Cd-induced exudation response, with concentrations increasing up to 11-fold. In soil, the rhizosphere microbial community of AC Hime, the cultivar with the strongest Cd-induced exudation, showed a distinct carbon utilization pattern, as revealed by Principal Component Analysis. These findings establish a clear link between a plant’s internal Cd retention strategy and its external chemical signaling to the rhizosphere. The research highlights the importance of symplastic compartmentalization as a key trait for breeding low-Cd accumulating cultivars and provides a foundation for understanding the intricate plant-microbe interactions in contaminated soils.