Impact of seed‐applied fungicide and insecticide on Azospirillum brasilense survival and wheat growth‐promoting ability

The use of Azospirillum brasilense as a crop inoculant has increased in recent years. Thus, the compatibility of the inoculation technology with seed treatments using pesticides needs to be evaluated. In this study, we evaluated the effect of an insecticide and fungicide formulation on A. brasilense strain FP2 population by culturing and culture‐independent approaches. In addition, we evaluated the impact of these pesticides on the ability of A. brasilense to promote plant growth by monitoring biometric traits (root and shoot dry mass and length) of wheat grown in Greenhouse conditions. Seed pesticide dressings, mainly fungicide, led to a significant mortality of A. brasilense over time. The ability of A. brasilense to promote wheat growth also decreased due to pesticide treatments combined with sowing delay. Considering that pesticides confer fitness advantages to the wheat in field condition, our results suggest that sowing within the first 4 h after inoculation maintain the beneficial effects of A. brasilense on wheat growth promotion. Furthermore, we conclude that inoculation and treatment of seeds with pesticides may be compatible techniques when carried out immediately before sowing. Significance and Impact of the Study: Wheat crop fields are adversely affected by biotic and abiotic stresses. Aiming to overcome these challenges, seed dressing with pesticides and Azospirillum brasilense have been widely used in wheat crop fields. The combination of culture and culture‐independent techniques allowed us to confirm that seed pesticide dressings, mainly fungicide, led to a significant mortality of A. brasilense which increased with storage time. Our results suggest that sowing within the first 4 h after inoculation maintains the beneficial effects of A. brasilense on wheat growth promotion.