Unveiling Pseudochrobactrum asaccharolyticum and associated rhizobacteria with Lepidium meyenii W.: PGPR potential and interaction with high Andean soil properties

Abstract

Intensive cultivation of maca (Lepidium meyenii Walp.) causes significant physicochemical degradation and a loss of microbiological resilience in High Andean soils. Native rhizobacteria-based biofertilizers emerge as a sustainable alternative to restore soil quality. This study explored the microbial diversity of the maca rhizosphere at extreme altitudes (>4000 m a.s.l.) and evaluated the potential of native isolates as plant growth-promoting rhizobacteria (PGPR). A total of 133 isolates were obtained using selective methodologies. Six elite strains were molecularly identified (16S rRNA gene) as Peribacillus, Pseudomonas, Pantoea, and notably, Pseudochrobactrum asaccharolyticum. Low microbial density was observed, likely linked to degradation from intensive monoculture. Microbial functionality was associated with soil management, enabling the identification of strains with high viability (>10¹⁰ CFU mL⁻¹) adapted to extreme conditions. In this study, the presence of P. asaccharolyticum was identified in association with maca crops. This species is of particular interest due to its previously recognized potential for soil bioremediation. These findings suggest functional specialization of the native microbiota and a high biotechnological potential for developing specific bio-inputs. These results contribute to mitigating monoculture impacts, restoring degraded soils, and promoting sustainable High-Andean agriculture.