Mechanism of the effect of Pseudomonas sp. AT2 on the growth of rice under atrazine stress

Atrazine residues in farmland soil readily pose a threat to sensitive crops following crop rotation. Employing functional microorganisms to regulate pesticide degradation in crops has emerged as an effective strategy to alleviate phytotoxicity. This study investigated the effect of atrazine on the microbial community and the abundance of atrazine-degrading genes in the rice rhizosphere soil. Furthermore, one atrazine-degrading bacteria Pseudomonas sp. AT2 was isolated and purified from rhizosphere soil. Pot experiments were conducted to explore the effect and mechanism of strain AT2 on rice growth and atrazine degradation. The results showed that atrazine significantly altered the structure of rice rhizosphere bacteria while increasing the abundance of atrazine-degrading genes TrzN, AtzB, and AtzC in the rhizosphere soil. In the presence of atrazine, the inoculation of strain AT2 significantly improved shoot and root elongation, dry weight, and chlorophyll content, and reduced MDA content, indicating that AT2 could alleviate oxidative damage in rice. Moreover, inoculation with strain AT2 promoted the degradation of atrazine in both the soil (with 14.9% decrease) and rice (with 47.1%-57.5% decrease) compared to the control. Under atrazine stress, rice inoculated with AT2 exhibited upregulated expression of some genes involved in atrazine degradation, with transcript levels 1.3-2.7 times higher than control. These findings demonstrate that colonization of degrading strains can facilitate the degradation of atrazine in the "soil-rice" system by activating the expression of degradative genes. This process helps alleviate the phytotoxicity caused by atrazine residues in the environment.