Effects of cypermethrin insecticide on the growth and plant growth-promoting activity of Burkholderia-like strain (UAGC867) and Pseudomonas-affiliated strain (UAGC97).

Brazil is a global leader in grain production, with corn reaching 122 million tons in the 2024/2025 harvest. Pest control, particularly of Spodoptera frugiperda, depends heavily on cypermethrin, a Class II hazardous synthetic insecticide with significant environmental risks. This study assessed the tolerance and degradation capacity of Pseudomonas-affiliated strain and Burkholderia-like strain in cypermethrin-contaminated environments, along with their indole-3-acetic acid (IAA) production and impact on early maize development. Both strains tolerated the insecticide and grew at varying concentrations, with Burkholderia-like strain showing superior degradation potential at 25 mg L⁻1. Microcosm respirometry indicated initial CO2 reduction post-inoculation due to microbial competition, followed by increased CO2 at 200 mg L⁻1, suggesting cypermethrin use as a carbon source by adapted microbes. IAA production by Burkholderia-like strain remained high despite contamination, whereas Pseudomonas-affiliated strain showed delayed synthesis. Growth assays revealed that Burkholderia-like strain (UAGC867) promoted shoot development and dry biomass accumulation in maize seedlings under cypermethrin stress, an effect not observed for Pseudomonas-affiliated strain. These findings highlight the potential of Burkholderia-like strain for bioremediation and plant growth promotion in insecticide-impacted agricultural systems, offering a sustainable approach to enhance productivity while reducing environmental harm.