P-376 - Effects of Fungicidal and Biological Seed Treatments on Soybean Microbiomes

Seed treatments are an important tool for improving agricultural plant productivity and for defending against pathogens and pests. Despite 90% of soybean crops in the U.S. having received a seed treatment in 2024, little is known about how different types of treatments influence the plant and soil microbiomes. In this study, we explored the effects of the commonly used, non-systemic fungicide fludioxonil or a strain of Bacillus amyloliquefaciens on the soybean spermosphere, rhizosphere, and root endosphere microbiomes after planting in natural field soil. Our approach was to focus on the effects of these seed treatments on microbiome assembly intensely within the first few hours and days after planting and then weekly after the 14^th day through the V2 growth stage. The concentration of the Bacillus spores was consistently high during the transition from an imbibed seed to radical emergence, but the concentration of spores decreased as the root developed. Overall, the treatments did not have a significant effect on root dry weight or nodulation compared to the untreated controls. We are currently using Nanopore sequencing to generate microbial community fingerprints based on the small subunit gene and ITS region. These microbial community profiles will provide a better understanding of the effects of seed treatments on the assembly of the soybean spermosphere, rhizosphere, and root endosphere microbial communities to better understand how seed treatments influence plant growth.