# Pseudomonas sp. UW4 ameliorates continuous cropping by optimizing soil nutrients and combating garlic oxidative damage

## TL;DR

This study shows how a specific bacteria helps garlic grow better in soil that has been continuously farmed by improving soil nutrients and reducing plant stress.

## Contribution

The study reveals how PGPB bacteria ameliorate continuous cropping stress in garlic through soil and plant-level mechanisms.

## Key findings

- Pseudomonas sp. UW4 improved soil nutrient levels and enzymatic activity in continuously cropped garlic fields.
- The bacteria reduced oxidative stress in garlic by enhancing antioxidant defenses and root vitality.
- PGPB inoculation restored rhizosphere microecology and improved nutrient cycling and plant growth.

## Abstract

Continuous cropping obstacles have emerged as a major global challenge to sustainable agricultural production, inducing severe soil degradation and ecosystem imbalance. While root-associated microbiota have demonstrated ecological potential in ameliorating continuous cropping disorders, the specific application mechanisms of Plant Growth-Promoting Bacteria (PGPB) in garlic (Allium sativum L.) under continuous cropping stress remain insufficiently explored. This comprehensive study systematically investigated PGPB-mediated improvements in garlic’s morpho-physiological traits, antioxidant defense systems, and rhizosphere soil microecology under continuous cropping conditions, with a particular focus on deciphering the PGPB-driven remediation mechanisms. Principal Component (PCA) and RDA Analysis identified malondialdehyde (MDA) and hydrogen peroxide (H₂O₂) accumulation as sensitive indicators characterizing oxidative stress in garlic seedlings under continuous cropping regimes. Concurrently, we observed significant depletion of critical soil nutrients (available phosphorus: AP; available nitrogen: AN) and enzymatic activities (neutral phosphatase, invertase, urease, catalase), accompanied by progressive soil acidification (pH reduction). Soil environmental degradation acts synergistically to disrupt the development of root structures, reduce the efficiency of nutrient acquisition and affect above ground to root nutrient conversion. PGPB inoculation effectively reconstructed the rhizosphere microecological network by enhancing the synergistic coupling between AP/AN dynamics and enzymatic catalysis (UW4 application increased sucrase, polyphenol oxidase, catalase activity, phosphatase activity and urease activity by 13.43%, 8.88%, 5.44%, 5.80% and 9.65%). Microbial engineering intervention optimized the soil microenvironment through pH homeostasis and enzyme activation, revitalized root vitality via improved nutrient cycling (34% increase in root activity index), enhanced antioxidant capacity (28% reduction in ROS levels) ensuring efficient photo-assimilate partitioning to aboveground organs. These findings demonstrate that PGPB-mediated mitigation of continuous cropping obstacles operates through rhizosphere microecological reconstruction, root system functional enhancement and whole-plant antioxidant system fortification, which provides fresh insights into the development of microbiological solutions to address agricultural sustainability challenges.